Beet, Carrot, Radish, and Sweetpotato Botany and Planting

Beet—Beta vulgaris, Chenopodiaceae

Carrot—Daucus carota, Apiaceae (Umbelliferae)

Radish—Raphanus sativus, Brassicaceae (Cruciferae)

Sweetpotato/Boniato—Ipomoea batatas, Convolvulaceae

Cultivars

Tropical Root Crops

Tropical root crops are planted primarily for their edible roots, tubers, corms, or cormels. In this regard, tropical root crops require a longer period of time to mature than many other vegetable crops. Some root crops take as long as 14 months to reach maturity. Some people also eat the edible leaves of sweetpotato/boniato, cassava, and taro. In the case of these crops, plants grown for edible leaves can be grown in cooler locations than would otherwise be possible. For pest control products, these crops are included in root and tuber vegetables.

Botany and Planting

Cultivars

Cassava—Known the world over by a variety of names, including manioc, yuca, mandioca, balinghoy, kamoteng, kahoy (Philippines), mogo (Africa), tapioca root (India), and manioc root in its native South America. Though the exact origins of cassava are unknown, it was likely domesticated between 7,000 and 9,000 years ago in the Amazon. This root crop is grown throughout the tropics and has become an important dietary staple in many parts of the world.

Varieties are often separated based of their cyanogenic glucoside (HCN) content into either low HCN, a.k.a. “sweet,” or high HCN, a.k.a. “bitter,” types. The term “bitter” comes from a bitter flavor that is commonly believed to accompany the HCN. Though no named varieties are currently known in southern Florida, ‘Senorita’ was locally popular in the 1980s, and attempts were made to introduce the CIAT variety ‘Mantiqueira’ at that time because it produced acceptable yields even with high levels of root-knot nematode infestation. The range of local genotypes covers a few unnamed clones that have been imported from various Caribbean basin countries. However, federal regulations prohibit further importation of cuttings or botanical seed.

Root development may occur as early as 28 days after planting, though it may take about six weeks before fibrous roots begin to thicken rapidly with starch granules. There does not appear to be any specific trigger to root thickening, but the number of roots that will eventually thicken is determined early in the life of the crop, with little change in the number of thickened roots after three months. A soil fertility analysis is conducted as a routine practice to ensure an adequate amount of potassium is maintained in the soil to improve root development for improved yield. The amount of nitrogen available to the crop is often limited because excessive nitrogen increases vegetative growth rather than the root development.

For people who are able to find cuttings, follow the technique developed by scientists at the International Institute for Tropical Agriculture (IITA) in Ibadan, Nigeria, where one makes 2-node cuttings, or ministakes, which can provide a 5-fold increase in the production of propagules from each parent cassava plant. According to IITA, “[t]hese ministakes are easily moved and protected in plastic sacks until they can be grown on and hardened in individual plastic bags or nursery beds before being planted in the field.”

It takes 8–12 months for cassava roots to reach maturity. Plants are often cut back two weeks prior to harvest, resulting in increased tuber size and yields about 10% higher.

Preferences for specific varieties of cassava used for edible leaves may exist among consumers, though the ability to satisfy these requests is very limited, given the very small number of varieties currently grown in the United States.

Tannia is widely grown and used in the tropics. It has been grown since 1963 on a limited commercial scale in south Florida, where it is typically planted in the spring because the crop requires 9 to 10 months to reach maturity and can be injured by frosts. Tannia can be propagated by several methods: (1) plant the top (head), (2) plant the whole main tuber, (3) plant pieces of the main tuber, or (4) plant individual secondary tubers. Propagative materials should be set 3 to 5 inches below the surface. ‘South Dade White’ produces white-fleshed cormels; ‘Malanga Amarilla’ produces a yellow-fleshed edible corm. ‘Vinola’ produces purple-fleshed cormels.

Taro—‘Malanga Isleña’ produces one large white-fleshed central corm; a few unnamed Polynesian types are grown for the Asian market. The name "taro" is generally used to refer to Colocasia esculenta, one of several major root crops in the Araceae (Aroid) family.

There are several important crops throughout the tropical regions of the world related to taro and grown in certain Florida locations. These include the giant swamp taro, the giant taro, and cocoyam. Each of these Aroids has several other common names in different regions of the world.

Information about taro in Florida is limited due to a small acreage. However, taro can be cultivated under both wetland and dryland conditions, with the latter referred to as “dasheens” in Florida. Most will mature in 6 to 10 months, with corms being dug up with modified potato harvesters in commercial production. The corms are washed of soil, sorted by size, and packed. The recommended cold room temperature for prolonged storage is 45°F–50°F with a relative humidity of 85.

Tropical sweetpotato or boniato—‘Picadito’ is the main variety grown in Miami-Dade County. Sweetpotato usually has shallow-lobed leaves and wine-colored skin with orange flesh. However, boniato, which is predominantly grown in Miami-Dade County, has deeply lobed leaves and wine-colored skin with white flesh.

It is illegal to import sweetpotato/boniato into the United States due to soil pests, such as sweetpotato weevils, and there is no program to produce disease-free planting material of ‘Picadito’ in Florida. Other sweetpotato growing states have developed red-skinned, white-fleshed sweetpotatoes, which may grow well in Florida and which may be available from those plant breeders or through certified slip producers.

In regard to other tropical root crops, such as daikon radish or turmeric, readers may refer to Chapter 5, “Ethnic Vegetable Production.”

The following tables list registered pesticides that should be integrated with other pest management methods. Additional information on integrated management methods can be requested from UF/IFAS Extension horticulture or agriculture agents. A list of local UF/IFAS Extension offices is available at https://sfyl.ifas.ufl.edu/find-your-local-office/.