2 Plants for Tropical and Interior Landscaping

Plant species that are native to regions around the equator are described as tropical. They are adapted to climate conditions with an average temperature of 18^οC (64.4^οF), no chance of frost, and considerable precipitation at least part of the year. Depending on the latitude, plant species may be adapted to tropical humid (rain forest) or tropical dry (savanna) conditions.

Rain forest vegetation is lush with tall trees and thick lianas forming a dense canopy that filters sunlight from the smaller trees, vines, palms, orchids, and ferns growing in the understory. Examples of plant adaptations for high humidity and competition for light include large leaves with waxy surfaces and pointed tips that shed water. More information about interesting plant adaptions for this hot, humid climate is available at this link to The Tropical Rainforest [New Tab].

Grasses, shrubs and trees of the tropical savanna are well adapted for climate extremes. Long tap roots, thick fire resistant bark, tree trunks that store water, leaf drop during the dry season, and storage organs like bulbs and corms allow plants to survive an extremely hot, long dry season and a very wet season. Learn about some of these unique plants at this link to The Savanna [New Tab].

Many tropical rain forest plants are available year round in temperate climates for use in interior landscaping. Some common indoor plants include Codiaeum variegatum  var. pictum (croton),  Dieffenbachia seguine (dumb cane), Dypsis lutescens (Areca palm), and Epipremnum aureum (devil’s ivy, golden pothos). The morphology of these plants can be readily recognized as belonging to particular family groups and related genera share identifiable morphology. It is often possible to use vegetative features alone to identify these family groups, relying on reproductive features only when needed. For example, the square stems and opposite leaf arrangement of Solenostemon x hybridus (coleus), an indoor house plant and outdoor bedding plant, can be recognized as a member of the mint family, Lamiaceae. The morphological characteristics used to identify some plant families and genera commonly used in interior landscapes are summarized below. Access to images of the genera is available at this link to the KPU Plant Database [New Tab].

Araceae – arum family

Members of the arum family are called aroids. There are over 100 genera and 2500 species distributed on every continent, with the majority in North Africa and Mediterranean regions. These moncots are known as much for their magnificent foliage as for their characteristic inflorescence. In natural habitats, they range from shrubs such as Dieffenbachia seguine and climbers such as Epipremnum aureum to enormous herbs with corms or tubers.

The leaves are mostly spirally arranged and often parallel but sometimes net-veined and either simple or compound. The petiole has a membranous, sheathing base. The roots of all species are adventitious (i.e., they can arise anywhere on the stem) and are without root hairs. Climbing and epiphytic aroids have two kinds of roots, ones that are absorbent and grow downwards into the soil, and clasping roots that grow into crevices, away from light.

Individual flowers are tiny, and are borne on specialized inflorescence called a spadix. In the majority of species the spadix is surrounded by a leaf-like bract called a spathe. The spathe is frequently colored and serves as a pollinator attractant. In most cases, aroids are pollinated by flies; the resultant fruits are typically berries. Species grown in interior landscapes will prefer bright, indirect light and moist, well drained fertile soils, and evenly warm temperatures. The ARACEAE family has many familiar shrubs and climbers for indoor containers, including:

• Aglaonema (Chinese evergreen)
• Anthurium (flamingo flower)
• Caladium (elephant ear)
• Dieffenbachia (dumb cane)
• Epipremnum (devil’s ivy)
• Monstera (split-leaf philodendron)
• Philodendron (philodendron)
• Scindapsus (silver pothos)
• Spathiphyllum (peace lily)

Arecaceae – palm family

The palms comprise a large family (more than 200 genera and 2650 species) of evergreen trees and rattans (climbers) with primarily tropical and warm temperate distribution (few in Africa). Palms such as Dypsis lutescens are immediately recognizable to most people, having spirally arranged, often very large leaves in terminal rosettes.

The slender, unbranched stem of the coconut palm (of tropical-island-paradise fame) is typical of many palms, but there are other distinctive shapes and sizes of palms. Palms are usually categorized as either feather palms (pinnate leaves) or as fan palms (palmate leaves), and may be stout or slender, solitary or suckering, and from dwarf to full-size.

Flowering is rare in indoor cultivation, except with some smaller species (especially Chamaedorea). Flowers are usually small, yellow, 3-parted and partially embedded in the flower stems. After successful pollination, palms generally produce a rounded, fleshy or fibrous drupe (seldom as large as a coconut nor as succulent as a date). Depending on the species, palms grown in interior landscapes will prefer indirect bright to low light and loose well drained soil with regular fertility. Genera commonly cultivated indoors in atriums and containers include:

• Caryota (fishtail palm)
• Chamaedorea (parlour palms)
• Chamaerops (european fan palm)
• Chrysalidocarpus (butterfly palm)
• Dypsis lutescens (areca palm)
• Howea (Kentia, sentry palms)
• Phoenix (date palm)
• Ravenea (majestic palm)
• Rhapis (lady palm)
• Trachycarpus (windmill palm)

Euphorbiaceae – spurge family

The spurge family is large with more than 300 genera and 7500 species of annual and perennial flowering herbs, shrubs, trees, and some climbers growing in tropical and temperate climates.  Some species are succulent and cactus-like and some are characterized by  milky sap that may be poisonous. Genera are commonly used in both indoor and outdoor landscapes for their colorful bracts and unusual forms. Tender species such as Codiaeum variegatum var. pictum, an ornamental shrub with attractive, multicolored foliage, is commonly used in interior landscaping.

Family members usually have simple or sometimes palmately compound leaves that may be sessile or petiolate, often with stipules, and alternately arranged on the stem. Species are frequently monoecious with a raceme or cyme inflorescence and often a radially symmetrical cyathium that is composed of 5 colorful bracts surrounding  the reproductive flower parts. The fruit is usually a capsular schizocarp.  Euphorbs grown indoors will prefer bright light and well drained soil with moderate to low moisture and fertility. Some examples of genera used for interior landscaping indoor include:

• Acalypha (chenille plant)
• Codiaeum (croton)
• Euphorbia (spurge)