Horticulture Principles and Practices

such as rosemary, sage, thyme, marjoram, basil, catnip, peppermint, lavender, and
spearmint. Apart from being useful for medicinal and culinary purposes, mints
are used as ornamentals in landscaping.
5. Solanaceae (nightshade family). The nightshade family is noted for the
poisonous alkaloids many of them produce (e.g., the deadly drug complex
called belladonna that is extracted from the nightshade plant). Other drugs
produced by this family are atropine, scopolamine, nicotine, solanine, and
hyoscyamine. Important vegetable plants in this family are tomato
(Lycopersicon esculentum), eggplant (Solanum melongena), pepper (Capsicum
spp.), and potato (Solanum tuberosum). Other important plants are tobacco
(Nicotiana tabacum) and petunia (Petunia hybrida). When potato tubers are
exposed to the sun, they produce a green color at the surface. These green areas
are known to contain toxins.
6. Apiaceae (carrot family). Plants in the carrot family frequently produce
numerous tiny flowers that are arranged in umbels. The plants of horticultural
importance include vegetables and herbs such as parsley, carrot, celery, dill,
coriander, and parsnip.
7. Cucurbitaceae (pumpkin family). The pumpkin or gourd family is characterized
by prostrate or climbing herbaceous vines with tendrils and large, fleshy fruits
containing numerous seeds. Important plants include pumpkin (Cucurbita
maxima), melon (Cucumis melo), watermelon (Citrullus lunatus), and cucumber
(Cucumis sativus).
8. Asteraceae (sunflower family). The sunflower family has the second largest
number of flowering plant species. Flowers in this family occur in a compact
inflorescence or head (Figure 2–31). Some of the members are edible and
others ornamental. Important plants include sunflower (Helianthus annuus),
marigold (Tagetes spp.), Dahlia spp., Chrysanthemum spp., Aster spp., and
edible plants such as lettuce (Lactuca sativa), Jerusalem artichoke
(Helianthus tuberosus), and endive (Cichorium intybus). The common
dandelion, (Taraxacum officinale), a noxious weed in lawns, belongs to this
family.
9. Euphobiaceae (spurge family). Most members of the spurge family produce
milky latex, and the family includes a number of poisonous species. The largest
genus in this family is the Euphorbia. Important plants include the Christmas
plant, or poinsettia (Euphorbia pulcherrima); a root crop, cassava (Manihot
esculenta); and the castor bean (Ricinus communis).
10. Rutaceae (rue family). Most of the species in the rue family are aromatic shrubs or
trees. An important and popular genus is the Citrus, which includes plants such
as mandarin, lemon, lime, grapefruit, and sweet orange.
11. Ericaceae (heath family). The heath family consists of shrubs that are adapted
to acidic soils. The genera of horticultural importance include Rhododendron
(rhododendron and azalea) and Vaccinium (blueberry and cranberry).
2.6.2 GYMNOSPERMS
Gymnosperms have naked seed. There are four divisions of gymnosperms with living
representatives: Cycadophyta (cycads), Ginkgophyta (ginkgo, maidenhair tree),
Coniferophyta (conifers), and Gnetophyta (gnetophytes). The most widespread of
these divisions is the Coniferophyta, which consists of about 50 genera and 550
species. The most familiar of all conifers are the pines of the family Pinaceae. The
important genera of conifers other than the pines are the firs (Abies), spruces (Picea),
hemlocks (Tsuga), Douglas firs (Pseudotsuga), cypresses (Cupressus), and junipers
(Juniperus). These predominantly evergreen trees and shrubs occur primarily in temperate
areas.
Gymnosperms
Plants that bear seeds that
are not within fruits
(naked).
2.6 Some Families of Horticultural Importance 59