Introduction
There are two basic types of marigolds: the large-flowered American (also referred to as African) marigold tagetes erecta and the smaller-flowered French marigold tagetes patula. A less well-known species, Tagetes tenuifolia, has smaller flowers and leaves than most other marigolds. Yellow, orange, golden, or bicolored flowers are held either well above the fine-textured, dark green foliage or tucked in with the foliage, depending on the cultivar. They brighten up any sunny area in the landscape and attract attention. As flowers die, they hang on the plants and detract from the appearance of the landscape bed. Cut them off periodically to enhance appearance. Marigolds may be used as a dried flower and are planted 10 to 14 inches apart to form a solid mass of color. Some of the taller selections fall over in heavy rain or in windy weather.
Credit: Edward F. Gilman, UF/IFAS
General Information
Scientific name: Tagetes tenuifolia
Pronunciation: tuh-JEE-teez ten-yoo-iff-FOLE-lee-uh
Common name(s): signet, signet marigold
Family: Compositae
Plant type: annual
USDA hardiness zones: all zones (Figure 2)
Planting month for zone 7: Jun
Planting month for zone 8: May; Jun
Planting month for zone 9: Mar; Apr; Sep; Oct; Nov
Planting month for zone 10 and 11: Feb; Mar; Oct; Nov; Dec
Origin: native to North America
Invasive potential: not known to be invasive
Uses: container or above-ground planter; edging; border; attracts butterflies; accent
Availability: somewhat available, may have to go out of the region to find the plant
Credit:
Description
Height: 1 to 2 feet
Spread: 1 to 2 feet
Plant habit: round
Plant density: dense
Growth rate: moderate
Texture: fine
Foliage
Leaf arrangement: opposite/subopposite
Leaf type: odd-pinnately compound
Leaf margin: serrate
Leaf shape: oblong
Leaf venation: not applicable
Leaf type and persistence: not applicable
Leaf blade length: less than 2 inches
Leaf color: green
Fall color: not applicable
Fall characteristic: not applicable
Flower
Flower color: orange; yellow; golden; bicolored
Flower characteristic: showy
Fruit
Fruit shape: no fruit
Fruit length: no fruit
Fruit cover: no fruit
Fruit color: not applicable
Fruit characteristic: inconspicuous and not showy
Trunk and Branches
Trunk/bark/branches: not applicable
Current year stem/twig color: green
Current year stem/twig thickness: thin
Culture
Light requirement: plant grows in full sun
Soil tolerances: clay; sand; acidic; loam
Soil salt tolerances: unknown
Plant spacing: 12 to 18 inches
Other
Roots: not applicable
Winter interest: not applicable
Outstanding plant: not particularly outstanding
Pest resistance: very sensitive to one or more pests or diseases which can affect plant health or aesthetics
Use and Management
Provide fertile soil and at least six hours of sun. Marigold holds up well during the hot summer days in north Florida if watered regularly. Mites and worms destroy the foliage in central and south Florida during the summer. Too much watering may cause dwarf types to rot. Too much nitrogen or shade causes leafy plants with few flowers. Marigold is suitable for summer use throughout the southeastern part of the country. Large plants may be transplanted if enough of the root system is dug up.
The seed germinates in one week at 70°F to 75°F. If the growing area is too hot the plants become leggy. Some horticulturists recommend setting the plants a little deeper than they were in the pot.
Many cultivars have been developed for flower color and plant size. One or more are usually available at local garden centers.
Pests and Diseases
Mites are the most frequent pest on marigolds, especially during hot weather. The leaves lose their green color and severe infestations cover the plant with fine webbing.
Tarnished plant bug causes distorted flowers and leaves.
Leafhopper causes cupping and in-rolling of leaf margins. The petioles are twisted, and the underside of infected leaves turn purplish as they are exposed to the sun. The branch tips and leaflets wilt, and the leaflets turn yellow and dry. New shoots develop below the point of attack. Dwarf varieties are more severely infested than taller types. The repeated killing of the branch tips delays flowering.
Greenhouse leaf tier webs the leaves or flower buds together. The insect feeds on the undersides of the leaves.
Slugs may be detected by the silvery slime trails they leave. Slugs can be controlled with slug baits used according to label directions.
Leafminers also can destroy the foliage.
Predatory mites and wasps have been used successfully for pest control.
Botrytis blight causes the flowers to turn brown and decay, especially in wet weather. A gray mold forms on the fading flowers. Pick off and destroy the infected flowers.
The same wilt that attacks China aster may infect marigold, particularly French and dwarf types. Infected plants wilt and die. Remove and destroy infected plants.
A leaf spot causes oval to irregular, gray to black spots on the leaflets. The spots may be speckled with black fruiting bodies. The disease starts on the lower leaves and progresses upward. Varieties of African marigolds are most susceptible.
Stems infected with wilt and stem rot turn brown and shrivel at the soil line. The foliage wilts and the plant dies. African types are most susceptible. Remove and destroy infected plants.
