UNITED STATES—Houseplant culture is a unique type of horticulture. It involves almost no gardening. Most houseplants live exclusively indoors. Many inhabit homes and offices that lack gardens. Only a few fortunate sorts get to occasionally enjoy mild weather in home gardens. Such indulgences are generally brief and sheltered. Most houseplants are innately vulnerable.
Of course, no houseplant is native to domestic situations. Every houseplant lives outside somewhere. Most are from lush tropical rain forests, where they must compete with other foliage for sunlight. Many are understory plants that naturally live within the partial shade of bigger tropical vegetation. That is why they adapt so efficiently to partial shade inside.
That is also why most houseplants actually want to live inside here. They do not like the chill of winter, even if mild. Many or most succumb to minor frost if too exposed. They are simply unaccustomed to it. Since they adapt to shelter and partial shade inside, they are also sensitive to direct sunlight exposure. Foliage that becomes too exposed can scorch.
A houseplant here might be a garden plant there.
Tolerance of weather is as regional for houseplants as it is for garden plants. That is one commonality of gardening and houseplant culture. The various species of Ficus that are common trees in landscapes of Los Angeles are strictly houseplants in San Jose. They tolerate the minor winter chill of Los Angeles, but not the slightly cooler frost of San Jose.
Some ferns are popular houseplants because, like tropical plants, they generally tolerate partial shade. However, many are less tolerant of the minimal humidity of home interiors. Regular watering can compensate. Irregular watering might be distressful for some ferns. Fortunately, most ferns can recover from brief desiccation, even if their foliage dies back.
Succulents are completely different. They are intolerant of partial shade, and crave sunny and warm situations. They are nonetheless popular for houseplant culture because they generally tolerate minimal humidity. Cacti prefer aridity, and are very susceptible to rot in damp conditions. Succulents wilt to warn before they succumb to deficiency of moisture.
Without bloom, the richly vibrant foliar colors of coleus, Coleus scutellarioides, rival floral color of other warm season annuals. Striking foliar patterns are as exquisite as any floral display. Growth is efficient through the warmth of spring. Foliage might last until autumn. Late in its season, spikes of tiny blue flowers can be trimmed off to promote more foliage.
With bright ambient sunlight, coleus is more perennial as a houseplant. However, it may get persistent with pesky bloom as it matures. Some who grow it prefer to let bloom, and then prune it back afterward. Recovery from such pruning can be slow. Vegetative stems, without bloom, root easily as cuttings even in water. New cuttings can replace old plants.
Coleus foliage is intricately variegated with countless combinations of green, chartreuse, yellow, orange, red, burgundy, pink, white and brown. Variegation can be symmetrical or random. Leaf margins may be deeply lobed or just serrate. Modern cultivars might be no better than old fashioned sorts. Mature plants can get as tall and broad as about two feet. Some stay lower.
Horticulturist Tony Tomeo can be contacted at tonytomeo.com.