Florida's climate allows homeowners to grow fresh, delicious vegetables nearly year-round. Basic vegetable gardening information, planting dates, reliable varieties, and much more can be found in the Florida Vegetable Gardening Guide, available from your county Extension office or online at https://edis.ifas.ufl.edu/vh021.
This publication is meant to be a companion document to the Florida Vegetable Gardening Guide. It is intended for the home gardener who prefers to use natural and organic materials and methods that are compatible with the philosophy of organic gardening. Commercial organic producers should refer to Introduction to Organic Crop Production https://edis.ifas.ufl.edu/CV118.
What is "organic"?
The term organic gardening is of fairly recent origin. The word organic describes the "natural method of gardening and farming" and is commonly attributed to J. I. Rodale, founder of the Rodale Institute and publisher of Organic Gardening magazine. However, the first documented use of the term was by Lord Northbourne in his 1940 publication Look to the Land. Today's organic gardeners acknowledge their debt to these promoters of good husbandry of the land.
Organic production standards for commercial farms fall under the National Organic Program (NOP). The NOP is managed by the United States Department of Agriculture and is a federally regulated consumer protection label for agricultural products. Commercial producers who want to advertise crops as organic must be certified if they gross more than $5,000 a year. Part-time market gardeners who gross less than $5,000 a year from organic products are not required to be certified, but they are required to comply with all regulations established by the NOP. Home gardeners who consume or freely share the bounty with friends and family are not required to be certified and, in fact, are not allowed to use any NOP labels or organic logos. For more information, visit the NOP website (http://www.ams.usda.gov/AMSv1.0/nop ), also listed in the Additional Resources section at the end of this document.
Be careful when buying garden supplies with the term organic on the label. Organic does not necessarily mean the product is approved for use in organic gardening or farming, but rather that the product contains organic material, or material that is high in carbon. The term certified organic is used only for commercial agricultural outputs—namely food, fiber, and seed, but not for inputs such as compost, manure, or soil. Products approved for use in commercial organic production (such as pesticides and fertilizers) will have the Environmental Protection Agency (EPA) label "For Organic Production" (Figure 1) or the OMRI (Organic Materials Review Institute) seal (Figure 2). The OMRI seal can also be found on numerous garden products sold at nurseries and home supply stores.
Seeds and Transplants
Organically produced seeds are now available from many online or mail-order catalogs as well as local garden centers. Organically produced transplants are not as widely available, but may occasionally be purchased at farmer's markets or from a certified organic producer. Currently, the demand for organic seeds and transplants exceeds supply, so these organic products can be more expensive than nonorganic products. Be aware that certified organic seeds of the crop and variety that you desire may not be available because the organic seed industry is still in development.
No matter the approach (organic or nonorganic), it is important to use a quality soil mix (medium) when growing transplants from seed. Sterilized, soilless mixes are readily available and minimize the risk of soil borne diseases and weeds. However, many commercially available mixes have synthetic wetting agents and starter fertilizers that are prohibited in commercial organic production. Therefore, purist organic gardeners should look for mixes approved for use in organic production or make their own by buying bulk ingredients and mixing by hand. A large trash can with a secure lid is an inexpensive container for mixing and storing soil mixes. Be advised that aluminum or plastic cans are probably much more acceptable than galvanized cans, which can impart zinc (Zn) to the soil.
There are several reliable recipes for organic soil mixes, but trial and error is the only way to know which blend works best for the seedlings you want to grow. One simple recipe is two parts compost, six parts peat moss or small pine bark chips, and two parts perlite or vermiculite. For best results, the mix should have a pH between 5.5 and 6.5; otherwise, some nutrients may not be accessible to the plants. If perlite is used, adjust the pH with dolomitic limestone (dolomite), which provides magnesium (Mg) as well as calcium (Ca). Since Mg is already present in vermiculite, regular agricultural limestone is sufficient to raise the pH if necessary. Add the liming material at a rate of 5 pounds to every cubic yard of mix. Be sure to mix the media in a well-ventilated area and wear gloves and a mask designed to trap fine particulates to avoid inhaling potentially harmful dust. If using the trash can approach, simply alternate the addition of ingredients until the can is no more than ¾ full, secure the lid, and roll until mixed. For a list of organic potting media suppliers and more media recipes, see Potting Mixes for Certified Organic Production on the National Sustainable Agriculture Information Service (ATTRA) website. Table 1 summarizes selected media ingredients allowed in organic production.
Fertilize transplants 10–14 days after germination with a soluble fertilizer such as liquid fish emulsion or liquid kelp; mix and apply according to product directions. Gardeners with an interest in using compost tea should refer to that section below. Transplants grown indoors need to be prepared for the more stressful conditions outdoors. Move the transplants outside for about a week and check them daily. They are ready to be planted in the ground when their stems are firm but not woody. Woody stems are a sign that growth has slowed, and these plants may have difficulty resuming active growth. Transplants should be planted prior to flowering to ensure rapid growth and establishment.
One key tenet of organic gardening is to increase the soil's organic matter content. A soil's organic matter consists of plant and animal residues (e.g., animal manures, plant manures (cover crops), compost) that are either fresh, partially decomposed, or fully decomposed. Florida soils typically contain less than 1.5% organic matter. It is possible to increase the organic matter in Florida's subtropical environment, but it takes regular additions of organic amendments over several years before an increase can be documented.
Organic matter is central to many beneficial ecological processes. Over time, organic matter is slowly transformed by earthworms and microorganisms, such as fungi, algae, bacteria, and beneficial nematodes, into soluble nutrients that plants use for growth and development. Organic matter also provides the following benefits:
Improves soil structure.
Improves the ability of soil to hold water, nutrients, and air.
Improves the "buffering" capacity of soil (i.e., improves the soil's resistance to sudden changes in pH).
Provides a source of carbon to sustain the biological life in the soil.
Stimulates microbial processes that help convert insoluble natural additives, such as ground rock, into plant-usable forms.
Suppresses nematode populations.
Recycles organic waste products.
Before adding any nutrients or amendments to the soil, all gardeners should submit a soil sample for analysis to a licensed soil laboratory.
Compost is decomposed organic matter that is produced by combining "green" organic materials, such as yard trimmings and food wastes, with "brown" organic materials, such as fallen leaves, animal or plant manure, or even unbleached paper. Mixing the green and brown materials with water and air encourages microbial decomposition. Some gardeners add organic fertilizers, topsoil, lime, or minerals to enhance the nutrient concentration of compost. There are many recipes and several methods of composting from which to choose. Table 5 provides a list of materials and what each might contribute to the compost. For more information regarding home composting methods, see Compost Tips for the Home Gardener https://edis.ifas.ufl.edu/ep323 and visit the UF/IFAS Composting Center http://sarasota.ifas.ufl.edu/compost.
Compost for the garden should be ready within 2 months to 1 year, depending on the time of year, type of materials added, and how intensely the compost is managed. When the compost is broken down into a somewhat homogenous mixture, smells sweet, and is not hot, it is ready for use as a mulch or soil amendment. At 2–3 weeks before planting, broadcast the compost over the entire garden and incorporate into the soil to a depth of 6 inches. If you have only a small quantity of compost, it may be mixed into the soil along each planting furrow.
Special consideration should be given to compost and other inputs used in school gardens, gardens for the elderly, and other at-risk populations. To minimize risk of illness, look for the US Composting Council's (USCC) Seal of Testing Assurance (STA) (Figure 3). The USCC regulations have specific time/temperature requirements to ensure pathogen destruction. The seal assures that the compost was made according to EPA standards and is of the highest quality. STA compost is considered certified pathogen-free for fecal coliform bacteria or Salmonella. The STA label is voluntary; thus there may be other compost suppliers offering properly composted manures with minimum risk of fecal coliform bacteria. These companies keep composting records and most provide certificates of analysis upon request. Most states require commercial facilities to obtain permits to sell compost. In Florida, permits can be obtained from the Department of Environmental Protection.
When animal manures are available, they are a very good source of nutrients and organic matter for the organic gardener. When obtained from a local source, transportation costs are minimized, a waste product is recycled, and the gardener learns first-hand about animal diets and litter materials. However, there are disadvantages of using raw manure, including its strong odor, plant damage resulting from its high salt and N concentration, and risks to human health due to the potential transfer of pathogens such as E. coli, Salmonella, and Listeria from animals to humans. For these reasons, it is always preferable to compost fresh animal manures. Composting removes most of the problems with raw manures and improves the quality of the organic matter being added to the garden. Please refer to the section on compost above to avoid many of the pitfalls of using raw manures. Manure from pigs, dogs, and cats should never be used in gardens because of the risk of contamination by parasites such as roundworm or tapeworm.
The National Organic Program has strict rules regarding the use of fresh animal manure for commercial vegetable production, and it is recommended that home gardeners follow them if using fresh (raw) manure. In certified organic systems, raw manure must be applied at least 90 days before harvesting a crop where the edible portion is not in contact with the soil (e.g., sweet corn) and at least 120 days before harvesting a crop where the edible portion does touch the soil (e.g., watermelons, potatoes). This practice is commonly referred to as the "90/120 day rule." Most composts contain N (nitrogen), P (phosphorus), and K (potassium), but may supply too much of one and not enough of the other, a problem frequently overlooked with organic sources. N availability in compost is slower than P and K availability because N must be transformed by microbes before plants can use it. For that reason, compost application rates might be best calculated based on P in P-sensitive areas of Florida. For an accurate recommendation, submit a sample of your compost to the UF/IFAS ESTL http://soilslab.ifas.ufl.edu/ESTL Home.asp for nutrient analysis.
Keep in mind that manure generally releases nutrients slowly and should be mixed into the soil before planting. Soil incorporation also reduces the potential for nutrient losses from runoff in heavy rains or volatilization of selected nutrients, such as N. Manures vary greatly in their nutrient content according to the type, age, and condition of the animal; the kind of feed used; the manure's age and moisture content; and the kind and amount of litter or bedding mixed in the manure. Table 3 shows nutrient concentrations of N (nitrogen), P (phosphorus), and K (potassium) as well as recommended application rates of raw manures based on their wet weights. Animal manures also provide most of the micronutrients needed by plants. Keep in mind that manure is not always a complete, well-balanced fertilizer. Depending on soil test results and the type of manure used, it may be advantageous to apply a complete fertilizer or ground rock phosphate and potash in addition to the manures. Because P, Cu (copper), and Zn (Zinc) are frequently added to poultry feed, repeated applications of poultry litter on the same location should be avoided. This practice prevents accumulation of heavy metals at concentrations toxic to plants and reduces the chance of P contaminating surface water like lakes and rivers. Many analytical labs offer manure analysis for a nominal fee. Gardeners who plan to use the same manure source for several years should consider having the source analyzed. Before planting, broadcast the manure evenly over the plot and spade, till, or otherwise work it evenly into the top 6 inches of topsoil. Clumps of partially decomposed organic matter not only interfere with planting, but may also result in nutrient deficiencies and possible soil borne disease problems, such as "damping-off" of young seedlings. Use the "90/120 day rule" described above for human and plant safety.
Some farmers and gardeners have reported damage to crops that has been associated with the class of herbicides known as pyridine carboxylic acids (PCA) (aminopyralid, clopyralid, fluroxypyr, picloram, and triclopyr). These herbicides are registered for use in pasture, row crops, roadsides, and some vegetables and fruits. In pastures, these herbicides are important to control toxic weeds that can sicken or kill grazing livestock. According to the Environmental Protection Agency, the compounds pass safely through the animal's digestive tract and are excreted as urine and manure. Typically, the compounds break down through natural processes (i.e., sunlight, heat, biological decomposition) within 30 days, but sometimes the compounds can persist in manure, compost, and baled hay, especially if stored in static piles. Persistent PCA herbicide activity has, on occasion, resulted in poor seed germination; twisted, cupped, or elongated leaves; and reduced fruit development. Keep in mind there are many factors that can cause these symptoms (e.g., disease, insects, herbicide drift from a neighbor). Gardeners should ask for a history of herbicide use prior to obtaining manure, compost, or hay. If in doubt, a simple test can be conducted (see Bioassay Test for Herbicide Residues in Compost: http://www.co.laplata.co.us/UserFiles/Servers/Server_1323669/File/Government/Departments/Weeds/Education%20and%20Resources/bioeassy_herbicide_compost.pdf).
Cover Crops and Green Manure
Cover crops are short-term plantings that benefit the garden, but are not grown for harvest. Cover crops
reduce soil loss during heavy rains,
provide habitat for beneficial insects, and
when in bloom, provide pollen and nectar for pollinators.
Cover crops in the grass family have large, fibrous root systems that are known to improve the soil's physical structure. Legume cover crops benefit the garden by providing a source of N for subsequent crops. Some cover crops also help to reduce nematode populations. For more information, see Additional Resources at the end of this publication.
Green manure is typically defined as a cover crop that is plowed into the soil while still fresh and green. Growing cover crops during the off season is a good way to give the garden a rest from tillage. Cowpea, velvet bean, soybean, and sunflower are recommended in summer (June through September), and cereal rye (cv. FL 401), crimson clover, and Austrian winter pea are recommended in winter (November through February). Buckwheat is easily grown during the cooler spring and fall seasons.
Compost tea is made by soaking or steeping compost in water and, in the process, extracting microorganisms. In theory, the beneficial microbes in the compost tea provide some protection against disease pathogens when the tea is applied to the soil or foliage. Because results depend on complex environmental and biological conditions, scientific studies on the effectiveness of compost tea to suppress pathogens are not consistent. Generally, there are many other cultural practices that can be used to discourage diseases (e.g., crop rotation, selecting resistant cultivars, etc.). Compost tea does not provide a measureable amount of nutrition to plants.
There are several recipes and methods for making compost tea. Make the tea with potable water and mature compost that has reached high temperatures (i.e., measured with a compost thermometer). Some recipes call for a sugar source to boost microbial activity, but gardeners should be aware that compost tea made this way can also increase the number of pathogens in the tea, and therefore that practice is discouraged by the National Organic Standards. While there are benefits to inoculating the garden with biologically active inputs, keep in mind that tea made from raw manures, even if solely plant-based, may contain microbes that are harmful to human health. To minimize risk of microbial-induced illness, wash hands with warm soapy water after gardening and before handling food, clean tools and surfaces that come into contact with food with an appropriate food grade sanitizer, and wash produce before it is consumed. More information about compost tea can be found in the Additional Resources section at the end of this publication.
UF/IFAS Extension encourages all gardeners to use appropriate rates of fertilizer and amendments in the garden and to follow local ordinances on the use of nitrogen (N) and phosphorus (P) to protect Florida's natural resources. Before adding any nutrients or amendments to the soil, all gardeners should submit a soil sample for analysis to a licensed soil laboratory. UF/IFAS offers a soil test for home gardeners for a nominal fee. Visit the Extension Soil Testing Laboratory's (ESTL) website http://soilslab.ifas.ufl.edu/ESTL Home.asp or check with your county Extension office http://solutionsforyourlife.ufl.edu/map/ for more information about how to collect and submit a soil, manure, or compost sample, and to obtain additional guidance about fertility management. Soil test results include a recommendation for fertilizer application based on the planned crops. The UF/IFAS ESTL can determine the percentage of soil organic matter for an extra fee. The section below provides an overview of the most common fertilizers used in the home garden.
Nutrients from Natural and Organic Fertilizers
Vegetables need a variety of nutrients. A primary nutrient refers to N, P, and K, which are used in considerable quantities by crops. Secondary nutrients refer to calcium (Ca), magnesium (Mg), and sulfur (S), which are used in moderate quantities by plants and influence soil pH. Sometimes, primary and secondary nutrients are grouped together and called macronutrients. Micronutrients, trace, or minor elements refer to the essential plant nutrients used in relatively small quantities. These micronutrients include boron (B), copper (Cu), iron (Fe), chloride (Cl), manganese (Mn), molybdenum (Mo), and zinc (Zn).
Nitrogen (N). Nitrogen is frequently the most limiting nutrient in vegetable production systems, and N management can be challenging in organic gardening because of the variability of N concentrations in organic amendments. Organic N must be converted by microorganisms into inorganic N (nitrate) before plant roots can absorb it. Furthermore, because the rate of N release depends on many environmental factors, such as temperature, soil moisture, and microorganisms, even the best estimate may not always reflect the actual release rate. Nevertheless, N from organic sources is typically sufficient to support crop growth.
The application of N depends largely on the crop's requirements and the form that is being applied. Soluble forms of N (often present in synthetic fertilizers) are avoided in organic gardening because of the philosophical opposition to using synthetic products, as well as the scientific observations that highly soluble nutrients contribute little to the soil biology. However, keep in mind that misapplication of N in any form poses a risk to ground and surface water quality.
Phosphorus (P). Phosphorus is plentiful in many Florida soils. Rock phosphates are natural deposits of phosphate in combination with Ca. The material is hard and yields P slowly (months to years). When finely ground and with impurities removed, the powdery material is only slightly soluble in water, but becomes available if and when the phosphate rock reacts with acids from the decaying organic matter in the soil. Colloidal phosphate is also available and widely used. A soil test will reveal whether additional P is needed. Since phosphate materials are so slowly decomposed, side dressings are seldom beneficial. Only the minimum amount of P should be used because of its negative impact on water quality.
Potassium (K). Potassium is widely distributed in nature, occurring in rocks, soils, plant and animal tissues, and in sea and lake water. In gardening, materials containing potassium, such as wood ashes, seaweed, potash salts, greensand, and ground rock potash, are used alone or in combination with other materials such as manure or compost. Since potash-bearing materials vary so much in composition and rate of decomposition, application rates must be determined for each.
Secondary and Micronutrients. An advantage of using organic materials as fertilizers is that these organic sources often contain many other elements that plants need in addition to N, P, and K. Plant nutrients are also found in naturally occurring materials such as marl (Ca), dolomite (Ca and Mg), limestone (Ca), and gypsum (Ca and S). Gypsum is used where Ca is needed, but a pH adjustment is not. Micronutrients are needed by plants in very small quantities and are present in many organic sources. For example, Mn is typically present in manure. Avoid phytotoxicity problems by applying micronutrients only when indicated by a soil or plant tissue test. Boron (B) is commonly sold as Solubor®. However, approved products containing other micronutrients (such as Zn, Cu, and Fe) can be difficult to locate. Try to find formulations that are chelated (or coated) with natural agents. Never apply foliar nutrients during the hottest time of day.
Lime. Reducing the acidity of the soil is the primary purpose for using lime in the garden. Lime should be applied only when the need has been established by a reliable soil pH test. Off-the-shelf soil pH test strips only provide a measure of the active acidity in the soil and are not an accurate method to determine the amount of lime needed. The UF/IFAS ESTL uses a special extraction (the Adams Evans buffer) to determine the amount of lime needed. Liming materials also provide nutrients for plant use. Natural liming materials that an organic gardener might use are limestone, dolomite, shell, and marl. All of these forms must be finely ground to provide maximum benefit to the soil and plants. Apply lime well in advance of the planting date, preferably 2–3 months before the garden is planted. Mix well with the soil and keep moist for best results. Application closer to planting time is permissible, but benefits will be delayed.
Developing a Fertilizer Plan
Many fertilizer products are approved for use in organic production. These nutrient blends are made of different combinations of organic materials derived from plants, animals, and natural deposits of rocks and minerals. In addition to store-bought bags and boxes of fertilizers and amendments, gardeners may want to use animal manures, compost, and/or cover crops in the garden. Most gardeners use some combination of all the above.
Gardeners who have a soil test-based recommendation can develop a plan to provide nutrients to crops with the following considerations: nutrient concentration, estimated percent of nutrient available during the season, and nutrient balance. Tables 3, 4, and 5 provide estimates of the nutrients found in common organic fertilizers and amendments. If manure or compost will be used, begin your fertilizer plan by first estimating the amount of N, P, and K the input will provide. Once the concentrations of these nutrients are determined, consider the rate at which they will become available to plants. For example, approximately 20% of the total N in horse manure will likely be available during the year; 50% from poultry manure. That percent is significantly lower for composted materials (e.g., 10% for composted horse manure, 20% for composted poultry litter, and 10% for vegetable waste). Although most gardeners estimate compost and manure rates based on N, compost can also contain a significant amount of P. Adding mature compost to garden soil slows the loss of P to the environment because the organic matter helps to hold the P in place. Gardeners should determine their application rates of N or P based on the nutrient that poses the greatest threat to local water quality.
The following example shows how to estimate the amount of compost and manure to apply. Applying 100 lbs of compost (containing 1.5% N) to 100 square feet of garden area provides 1.5 lbs of potentially available total N per 100 square feet. Assuming 10% of that N will be available to plants after microbial transformations, only 0.15 lbs is useable by plants during the season. Using a similar calculation, but this time with broiler house poultry manure (containing 3.6% N), 100 lbs of manure applied to 100 square feet of area provides 3.6 lbs of potentially available total N. However, poultry manure is much more readily transformed by microbes. In fact, 45% of the total potential N will likely be available for an estimated 1.62 lbs of N useable by plants during the season. Based on nutrient rates recommended for commercial, diversified vegetable producers, gardeners should apply 0.46 lbs N, 0.40 lbs K2O, and 0–0.34 lbs P2O5 for every 100-square-feet of garden depending, again, on local conditions.
If the P and K concentration is low in your manure or compost, you can obtain these two nutrients from other sources. Slowly available P sources, such as rock or colloidal phosphates, limit risk to the environment while providing valuable nutrients. Apply at the rate of 2–5 pounds per 100 square feet of garden soil. If compost is being applied, add 2½ pounds phosphate per 25 lbs compost. Broadcast the material over the soil surface and work into the top 6 inches of soil before planting. Potassium is soluble in the soil and quickly available. Ground rock potash at 5 pounds per 100 square feet may be incorporated into the soil 3 weeks before planting. Langbeinite (Brand name: Sul-Po-Mag®) is used at 1 pound/100 square feet.
Liquid fertilizers can provide plants with nutrients in the short term. These fertilizers are derived from fish, seaweed, compost, and other materials and may be good sources of N and micronutrients. These fertilizers can be applied to the root zone or the plant leaves to complement fertilizer applications to soil.
There are numerous off-the-shelf fertilizer products to choose from. Remember to follow the label's instructions and not to exceed the UF/IFAS recommended fertilization rates. Finally, to ensure the nutrients in the garden are available, manage the soil pH when needed by adding lime. In most Florida soil conditions, applications of 2–5 pounds of finely ground dolomitic limestone per 100 square feet increases the soil pH by one unit.
When irrigating the garden, apply enough water to thoroughly moisten the root zone. A section of bed that is 1 foot wide by 1 foot deep and 100 feet long requires 24 gallons of water. On average, about ¾ of an inch of water can be stored in every foot of soil. Light sprinklings every day merely tend to wet the surface and encourage shallow root growth. Excess irrigation pushes valuable nutrients below the root zone and out of reach of plants. Drip or trickle irrigation is encouraged as a method for conserving water. Drip irrigation uses water up to 35% more efficiently than overhead sprinklers because the water is placed directly on the soil. Established plants need water at least weekly, either by rainfall or irrigation. Most water from wells in Florida is high in Ca and Mg and increases the pH of the soil. If you plan to irrigate from well water, be careful not to add too much lime to the soil.
Mulch refers to any material placed on the soil surface around plants. Mulch provides the following benefits: (a) conserves soil moisture, (b) conserves nutrients, (c) reduces soil erosion, (d) reduces crop loss from nematodes, (e) reduces weed growth, (f) provides a barrier between fruit and soil, thus reducing rotting of fruit, and (g) moderates soil temperature. Organic mulch can attract many insects, including beneficial spiders and ground beetles, but may also attract organisms like slugs or snails that can damage crops. Organic materials most commonly used for mulching are oak leaves, grass clippings, Bahia hay, pine straw, and mature cover crops, which have been cut and returned to the garden as mulch. Apply mulch before or after seeding or transplanting. Generally, 3–4 inches of moderately packed mulch is recommended to prevent weeds. Hardwood or pine mulch chips are best used in walkways and border areas around the garden. These mulches are slow to break down, provide a surface to walk on when the garden soil is wet, and can reduce weeds. Adding a weed barrier or even several layers of newspaper under the chips reduces weed growth even further. The most affordable way to purchase mulch is in volume. Mulch is typically sold by the cubic yard. One cubic yard (yd3) covers 100 square feet spread 2–3 inches deep.
At the end of the garden season, organic mulch may be removed and composted or incorporated into the garden soil. If the mulch consists mainly of dry and woody plant stems (which have a high concentration of carbon), add manure or other N-rich organic fertilizer to promote their decomposition.
Synthetic mulch materials, including plastic, are allowed and used frequently in commercial organic systems in combination with drip irrigation. These mulches can be reused for several seasons before needing replacement. Black mulch and Infra-Red Transmitting (IRT) mulch increase soil temperature—an advantage in the winter season. White mulch reflects the sun's rays and keeps the soil cooler than other types of mulches. White mulch is best used when daytime temperatures are high enough to slow plant growth. Clear plastic mulch has the disadvantage of allowing weeds to grow underneath it because of light penetration. Gardeners relying on compost and other solid materials to fertilize their crops need to apply those materials before laying down synthetic mulch.
The main objective of many organic gardeners is to produce food that has not been exposed to synthetic pesticides. Pests include weeds, insects, diseases, nematodes, and even animals like raccoons and birds. The first step to effective pest management is good cultural practices, such as observing correct planting dates, using fertilizer and water appropriately, rotating crops, and controlling weeds that harbor certain pests. Selecting vegetable varieties that are resistant or tolerant of pests is another approach that should be integrated into a home gardener's pest management plan. Seed catalogs, seed packets, and transplant labels often indicate pest resistance. For example, a tomato variety name may be followed with VFNTA indicating that it is resistant (in this case) to Verticillium (V) and Fusarium (F) wilt diseases, Nematodes (N), Tobacco Mosaic Virus (T), and Alternaria fungus (A). The Florida Vegetable Gardening Guide (https://edis.ifas.ufl.edu/vh021) provides an extensive list of "no-pesticide" approaches to pests. Table 6 provides a list of pesticides that are approved for use in organic vegetable production.
Crop Rotation. Changing the location of crops within your garden is called rotation. Rotation is an essential component to pest management because it interferes with the life cycles of pests in the soil (such as nematodes and soil borne diseases). Many pests are attracted to plants that are in the same plant family. For example, bell pepper, tomato, and eggplant are in the family Solanaceae. Avoid planting crops from the same family in the same section of the garden in consecutive seasons. Some pests can persist in the soil for years, so it may be necessary to allow several planting seasons or years to pass before repeating a crop in a problematic section of the garden. Moving the garden plot from one part of the yard to another is also helpful.
Many gardeners find it helpful to draw a sketch of the garden and the succession of crops to be planted. Try to plan at least 2 years in advance; 3–5 years is even better. Refer to the Florida Vegetable Gardening Guide (https://edis.ifas.ufl.edu/vh021) for planting dates and plant families to help plan crop succession.
Weed Management. A few herbicides are labeled for use in organic systems, but they are expensive and not very effective. When it comes to controlling weeds, prevention is best. As previously discussed, mulches are effective at preventing weeds. Select a garden site that is as free of weeds as possible. But fair warning, just because weeds are not currently present as plants, weed seeds are definitely present below the soil surface. Some weed seeds can survive in the soil for hundreds of years, so you most likely have a weed seed "bank" in your soil that is just waiting to germinate. They are naturally managed to some extent by diseases that kill them and insects, microbes, and small rodents that consume them. Weed seeds may be introduced into the garden in transplants, improperly prepared compost, plant mulches, and animal manures.
After the initial soil preparation for the garden is complete, it is beneficial to avoid disturbing the soil surface so new weed seeds are not exposed. Weeds are best controlled when they are small and have not begun to consume soil nutrients. Hand pull weeds or use one of the many excellent hand tools available for weed control. Only shallow cultivation is advised so as not to damage the crop root system. If weeds are too large to cultivate with hand tools, then cut them off at the soil with pruning shears. Never allow weeds to flower and produce seeds, or they will reseed themselves and reappear in the future.
Nematode Management. Nematodes are microscopic worms that feed on roots and seriously reduce growth and yield. Some vegetables, such as okra, are more susceptible to nematode attack. Others, like 'California Blackeye 5' pea, are tolerant of nematode damage and continue to produce fruit even when nematodes are present. Many kinds of nematodes can damage plants. Sting nematodes cause roots to appear stunted or "stung." Root knot nematodes infect roots and form galls—swollen areas in the root that contain female nematodes and their young. Do not confuse these galls with another type of swollen growth called nodules. Nodules are formed by Rhizobium, a beneficial bacterium that inhabits root systems and provides N to leguminous plants. Nodules are easily distinguished from galls because they turn pink when sliced open and are easily removed from the root (Figure 4).
Nematode damage is less likely in soils with high levels of organic matter and where crops are rotated so that members of the same family are not planted repeatedly in the same area. Excessive nematode populations may be reduced temporarily by "soil solarization" (Table 2) and other techniques described in Nematode Management in Organic Agriculture (https://edis.ifas.ufl.edu/ng047). See Additional Resources for more information.
Insect/Mite Management. Florida is home to many insect and mite pests and a host of beneficial organisms that naturally suppress them. Certain cover crops attract beneficial insects. Another approach is to plant a border of flowering plants known to attract natural enemies. Examples of such plants include sunflower (Helianthus spp.), mustards (Brassica spp.), alfafa (Medicago sativa), and Queen Ann's lace (Daucus carota). Buying and introducing beneficial insects into the home garden is expensive and seldom necessary.
Research studies have shown that excess N increases insect and mite populations. This finding creates a balancing act for gardeners who must provide enough N to grow a good crop without attracting pests. Weather patterns can also influence insects and mites. For example, hot, dry conditions tend to be associated with spider mites. It is a good idea to scout the garden weekly. Many insects are small even as adults and prefer to remain out of direct sunlight. Check the undersides of leaves, inside the whorls of new growth including flower buds, and at the soil surface near the base of plants. See Additional Resources for more information.
Disease Management. Diseases must be prevented because there are few curative controls available. Sanitation, resistant varieties, biological controls, rotation, and other cultural practices are common approaches to disease prevention. Sanitation practices include avoiding introducing diseased transplants into the garden and disinfecting tools following use. Sanitizing materials, including hydrogen peroxide, chlorine, and sodium hypochlorite (plain bleach), are generally allowed for use in organic production systems for sanitation purposes. Prevent crop-to-soil contact by staking or mulching. Avoid keeping the plants and soil too wet by using raised beds and drip irrigation. Water only during daylight hours and allow vegetable foliage to dry before moving through the garden.
In organic gardens, pest management relies primarily on cultural practices; pesticides should be used only as a last resort. For more information about pest management in the home garden, refer to https://edis.ifas.ufl.edu/topic_vegetable_garden_pests and the Florida Vegetable Gardening Guide (https://edis.ifas.ufl.edu/vh021).
When problems persist, it may be wise to submit a plant and/or soil sample for diagnosis to your local UF/IFAS Extension office. Contact information for UF/IFAS Extension offices is located at http://solutionsforyourlife.ufl.edu/map/. Your local UF/IFAS Extension agent may refer you to one of UF/IFAS's diagnostic labs listed in Additional Resources.
ATTRA (National Sustainable Agriculture Information Service)
Search here for publications on compost tea, seed and fertilizer sources, alternative soil testing labs, and more.
FOG (Florida Organic Growers and Consumers, Inc.)
OMRI (Organic Materials Review Institute) http://www.omri.org/
Search here for a list of allowed materials and organic seed sources.
University of Georgia Extension
How to Convert an Inorganic Fertilizer Recommendation to an Organic One
SARE (Sustainable Agriculture Research and Education)
NOP (USDA National Organic Program)
Compost Task Force Report
UF/IFAS EDIS Publications of Interest to Organic Gardeners
Florida Vegetable Gardening
Florida Vegetable Gardening Guide: https://edis.ifas.ufl.edu/VH021
Minigardening (Growing Vegetables in Containers): http://ufdcimages.uflib.ufl.edu/IR/00/00/34/28/00001/VH03200.pdf
Growing Potatoes in the Florida Home Garden: https://edis.ifas.ufl.edu/HS183
Index for specific vegetable guidelines: https://edis.ifas.ufl.edu/TOPIC_Vegetables_A_thru_Z
Growing Heirloom Tomato Varieties in Southwest Florida: https://edis.ifas.ufl.edu/HS174
Compost and Soil Amendments
Compost Tips for the Home Gardener: https://edis.ifas.ufl.edu/EP323
Producing Garden Vegetables with Organic Soil Amendments: http://ufdcimages.uflib.ufl.edu/IR/00/00/33/94/00001/MG32300.pdf
Cover Crop Benefits for South Florida Commercial Vegetable Producers: https://edis.ifas.ufl.edu/SS461
Cover Crops: https://edis.ifas.ufl.edu/AA217
Management of Nematodes with Cowpea Cover Crops: https://edis.ifas.ufl.edu/IN516
Biological Control for Insect Management in Strawberries: http://www.hos.ufl.edu/protectedag/EDIS/HS18000.pdf
Coping with Deer Damage in Florida: https://edis.ifas.ufl.edu/UW128
A Series on Diseases in the Florida Vegetable Garden: Tomato: https://edis.ifas.ufl.edu/PP121
Insect Management in the Home Garden: https://edis.ifas.ufl.edu/VH036
Management of Nematodes with Cowpea Cover Crops: https://edis.ifas.ufl.edu/IN516
Natural Enemies and Biological Control: https://edis.ifas.ufl.edu/IN120
Nematode Management Using Sorghum and Its Relatives: https://edis.ifas.ufl.edu/IN531
Nematode Management in Organic Agriculture: https://edis.ifas.ufl.edu/ng047
Diagnostic Labs and Clinics of the UF/IFAS
Plant Disease Clinic: http://plantpath.ifas.ufl.edu/extension/plant-diagnostic-center/
Insect Identification Service: https://edis.ifas.ufl.edu/sr010
Florida Nematode Sampling Instructions: https://edis.ifas.ufl.edu/SR011
The Florida Plant Diagnostic Network: https://edis.ifas.ufl.edu/PP151
Soil Testing Laboratory: http://soilslab.ifas.ufl.edu/
Landscape and Vegetable Garden Test Information Sheet: https://edis.ifas.ufl.edu/SS187
Altieri, M. A, C. I. Nicholls, and M. A. Fritz. 2005. Manage Insects on Your Farm: A Guide to Ecological Strategies. Beltsville, MD: Sustainable Agriculture Network. To purchase: 301-374-9696 or http://www.sare.org/WebStore
Free online version: http://www.sare.org/publications/insect/insect.pdf
Caldwell, B., E. B. Rosen, E. Sideman, A. Shelton, and C. Smart. 2005. Resource Guide for Organic Insect and Disease Management. Geneva, NY: Cornell University.
Free online version: http://web.pppmb.cals.cornell.edu/resourceguide/
To purchase: 315-787-2248 or http://calsbookstore-lamp.cit.cornell.edu/catalog/
Coleman, E. 1995. The New Organic Grower. White River Junction, VT: Chelsea Green.
To purchase: 800-639-4099 or www.chelseagreen.com
Ellis, B., and F. M. Bradley (eds.) 1996. The Organic Gardener's Handbook of Natural Insect and Disease Control. Emmaus, PA: Rodale Press.
Stephens, J. M. 1988. Manual of Minor Vegetables. Gainesville: University of Florida Institute of Food and Agricultural Sciences.
Stephens, J. M. 1999. Vegetable Gardening in Florida. Gainesville: University Press of Florida.
More for-sale resources about Florida vegetable gardening and pest management are available through the UF/IFAS Extension Bookstore: 800-226-1764 or http://ifasbooks.ifas.ufl.edu/
Common ingredients for a soilless organic potting media.1
Soil sterilization methods for the home gardener.
Raw manure nutrient concentration and recommended application rates on vegetable gardens 90–120 days in advance of harvest.1, 2
Average nutrient content of plant and animal materials suitable as organic fertilizer (percentage based on dry weight).1
Average nutrient content of mined or natural amendments used in organic production (percentage based on dry weight).1
Pest management products for organically managed home gardens.1