Tropical plants make a smooth transition as houseplants

Houseplants live outside somewhere.

Hibiscus, bougainvilleas, philodendrons and so many of the tropical and subtropical plants that we can enjoy in our gardens can only survive through winter in greenhouses in most other climates in America. Many of our tropical houseplants though, seem to be the same everywhere. Houseplants are generally grown in our homes not because they can not survive in our gardens, but because they ‘can’ survive in our homes.

Yes, houseplants are merely any plants, tropical or otherwise, that we grow in our houses. Yet, most and perhaps almost all of the plants that are best adapted to surviving as houseplants happen to be tropical plants. Tropicals do not need the seasons that they would get outside. Because many are native to dense and very competitive tropical forest environments, they are adapted to the sort of shade that they get in our homes, and survive on minimal volumes of soil that they have available while potted.

Nonetheless, they miss their tropical lifestyles. They only tolerate dry interior air, but would prefer more humidity. They would likewise prefer to be rinsed of dust more often than they can be in indoors. A regular supply of fresh organic debris to supply nutrients would be nice. However, if merely fertilized instead, tropicals are sensitive to salts and other toxins that eventually accumulate in the soil.

This is why some of the more resilient houseplants like to be brought outside for a gentle rinsing during a mild rain. As long as it is not too cool or windy, gentle rain rinses dust from the foliage and toxins from the soil. Plants can be brought out in the morning and brought in late to get as much time out in the rain as possible, but should not be left out overnight when it may get too cool. Even though they do not need any more moisture, plants can be watered by hose a few times to allow water to rinse freely through the soil.

Plants in overly decomposed potting soil are easier to repot with fresh soil while they are outside. Those that do not need to be repotted might still like getting grungy and potentially toxic mineral deposits scrubbed from their pots and drainage pans.

Burro’s Tail

Burro’s Tail is old fashioned, but can also be contemporary.

Back when big spider plants or Boston ferns suspended in fancy beaded macrame were all the rage through the 1970’s, burrow’s tail, Sedum morganianum, was an unusual but also trendy succulent perennial for sunny spots in the home or sheltered and slightly shaded spots in the garden. The refined foliar texture and light bluish green color contrasted nicely with the big and deep green leaves of comparably trendy philodendrons. The thin stems are too limber to stand up, but cascade excellently. Plants in the garden that get pruned back while dormant in winter can easily get two feet long through summer. Without pruning, big plants can get longer than six feet. Pruning scraps and even the small but plump leaves can be rooted and grown into new plants. It is impossible to prune or even move burro’s tail without dislodging some of the leaves anyway. Watering should be regular but not excessive, but then minimal for plants in the garden through winter.

Potted Plants Need Work Too

Most potted plants would prefer to be in the ground, . . . if possible.

Potted plants can be a problem any time of the year. Some want more water than get. Most get too much water or do not drain adequately. Large plants get constricted roots if pots are too small. The roots of some plants get cooked in exposed pots that collect too much heat from sunlight. Besides, too many pots just seem to be in the way in otherwise useful spaces on decks, patios and anywhere else trendsetting landscape designers want to put them.

Now that the weather is getting cool and rainy, potted plants are not as active as they were during warm weather. Many are dormant. Although few demand the attention that they got during warmer weather, plants still need to be tended to appropriately through autumn and winter.

Cool season annuals, which are also known as ‘winter’ annuals, should get groomed as long as they are performing in the garden, just like warm season annuals get groomed through summer. Deteriorating flowers should be plucked from pansy, viola, primrose, Iceland poppy, calendula, dianthus, stock, chrysanthemum and cyclamen because they can mildew and spread mildew to developing flowers and foliage. Unplucked cyclamen and calendula can develop seed which diverts resources from bloom.

Pots that are out in exposed areas will not need to be watered while they get enough water from rain. The problem is that many that do not drain adequately can get too much water from rain and stay saturated. Dormant and defoliated plants do not need much moisture at all. Even evergreen plants do not need as much as they do while active during warm weather, because cool and humid weather inhibits evapotranspiration (evaporation from foliar surfaces).

Potted plants under eaves also need less water while the weather is cool and humid, but need to be watered nonetheless because they are sheltered from rain. Plants in hanging pots typically drain and dry more efficiently, so probably want a bit more water. Even a few sheltered small plants in the ground may occasionally want to be watered during rainy weather if they do not extend enough roots where they can get moisture from rain beyond the sheltered area. Sheltered plants are actually the most likely to be neglected because watering does not seem so important when it is raining.

Angel Wing Begonia

Begonia involucrata at Monte Verde

The simple pink or sometimes red or white flowers of angel wing begonia are not as flashy as those of other begonias, and are not abundant enough to provide much color. During warm weather, they are merely a minor bonus to the striking foliage. As the name implies, the big and angularly lobed leaves are shaped like wings of angels. Upper surfaces are glossy and dark green with irregular silvery spots. Undersides are even glossier and reddish bronze. With support, the lanky cane stems can get more than twelve feet tall. However, because older tall canes produce runty foliage, they are often pruned out to promote more vigorous and lushly foliated young canes.

Because they are sensitive to frost, and also because they are ideal houseplants, angel wing begonias are typically grown in containers. They like rather regular but not excessive watering, and rich potting soil. Abundant sunlight enhances foliar color; but harsh exposure roasts foliage. Partial shade is not a problem.

Philodendron selloum

Philodendron selloum is unfamiliar with autumn.

There are all sorts of philodendrons with all sorts of fancy names. Yet, the biggest and boldest lacks a common name (at least one that is actually ‘common’), and is most popularly known by a Latin name that is not even correct. The proper name for Philodendron selloum is really Philodendron bipinnatifidum. It is a big awkward plant with big and deeply lobed leaves on long petioles (leaf stalks), and weirdly thick aerial roots. Well exposed plants can stand on wobbly trunks. Partly shaded plants can creep along the ground, and prefer to grab onto and climb tree trunks, fences or anything that they can get a hold of. The aerial roots are harmless to trees, and generally too slow to catch a healthy cat, but will take paint off of walls. All parts of Philodendron selloum are toxic.

String Of Pearls

Weird but elegantly pendulous string of pearls likes to hang around. It cascades nicely from hanging pots or tall urns.

It is difficult to see how string of pearls, Senecio rowleyanus, is related to much more colorful daisies and asters. The small, fuzzy and sickly white flowers are not much to look at, and only clutter the elegantly pendulous and oddly succulent foliage. The round leaves are light bluish green, so actually resemble peas more than they resemble pearls. The stems are so very thin and limber that they can only stand a few inches high, but can cascade to three feet!

Although evergreen, stems of outdoor plants can be cut back while dormant through winter to promote fresher growth in spring. The pruning scraps are very easy to propagate as cuttings. Roots are undemanding and sensitive to rot, so should be allowed to get nearly dry between watering. Bright ambient light without too much direct sun exposure is best. Incidentally, all parts of Senecio rowleyanus are toxic.

Coleus

Coleus works both inside and out.

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.

Houseplant Culture That Contradicts Gardening

Some ferns are popular as houseplants.

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. 

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. The 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.

Coleus

No flowers needed with this foliage!

Out in the garden, coleus, Plectranthus scutellarioides, prefers partial shade where the foliage is less likely to get roasted during arid and warm summer weather. It is grown as a warm season annual instead of as a perennial, because it gets so tired through winter, and can be killed by even a very mild frost. Its sensitivity to exposure in the garden is probably why it is more familiar as a houseplant.

The flashy and sometimes deeply lobed foliage is variegated with any combination of green, chartreuse, yellow, orange, red, burgundy, pink, white, brown and almost black. Flower spikes should be snipped as they develop to keep foliage dense. The tiny purple flowers are not much to brag about anyway. Large plants can get to two feet tall and broad. Cuttings root easily in rich and regularly moist potting soil or just plain water. Seeds need sunlight to germinate, so should only be pressed onto the surface of damp potting soil without getting covered, and misted daily.

Houseplants Bring The Outdoors In

Many houseplants will not live outside.

There is someplace in the world for the brethren of each and every houseplant to grow wild. All houseplants do not originate from the same regions, and many were bred in cultivation, but all originate from somewhere. They are houseplants only because they are plants that can live in a house.

Most houseplants are from tropical regions, and many are understory plants that grow in the partial shade of taller trees. They are naturally tolerant of the mild temperatures and partial shade within the home. Not many deciduous plants will be happy without a winter chill.

Confinement is also a concern, since houseplants need to be potted, and stay below ceilings. Plants that need to disperse their roots will not work. Neither will plants that can not be pruned down as they grow. Some palms that work well in malls have leaves that get longer than the distance between the floor and ceiling in the home!

Most houseplants are grown for foliage instead of flowers, not only because a lack of seasons inhibits bloom, but also because their foliage is naturally so appealing. African violets are one of the more notable exceptions. Amaryllis is all flower with almost no foliage, but typically gets discarded when done blooming.

Coleus and caladiums have such colorful foliage that there is no need for flowers. Bloom actually compromises their foliar quality anyway, which is why flower spikes get snipped from coleus. Mauna loa lily is grown for excellent rich green foliage, but sometimes adds clear white blooms as a bonus.

All sorts of ferns are very good houseplants. However, a few, including the popular Australian tree fern, produce coarse fuzz that can be irritating to the skin. A few others, like sword fern, produce messy spores that can permanently stain fabric and carpet. Just because they can live in the home does not mean that they should.

The various ficus are excellent houseplants because they can grow quite large, but can also be pruned to fit into their particular situations. The popular weeping fig (Ficus benjamina) has an abundance of small glossy leaves. Rubber tree and fiddle leaf fig have big thick leaves. Creeping fig is even more distinct from the others, as a wiry vine that is popularly grown in hanging pots.