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.

Not All Plants Like Fads.

Ornate pots and planters can be as decorative as the plants within them, and provide extra accommodation for more plants.

Like so many fads too often are, container gardening is overrated, and is actually contrary to the currently most faddish of fads; sustainability. Plants in containers need more regular watering than those that can disperse their roots more extensively into the ground. Those that are so indulged also want fertilizer to be applied more regularly, but are more likely to be damaged if fertilized too generously. Because confinement is stressful, plants in containers are innately more susceptible to disease and pests. Some plants need more pruning for confinement.

Then there are the problems with the containers. If exposed to sunlight, thin plastic containers get warm enough to cook roots within. Pots that do not drain adequately or that sit in their own drainage basins can stay saturated enough to kill roots. Water in drainage basins allows mosquitoes to proliferate. Seepage from large pots can rot decks and stain pavement. Self watering containers work nicely for houseplants (if used properly!), but lack drainage, so can not be used out where they are exposed to rain.

The advantages to container gardening are actually quite limited. Containers are obviously needed for houseplants, and where exposed soil is not available, like on balconies. They are also convenient for plants that want better soil than they can get in the garden, especially if the rest of the garden is responsibly landscaped with sustainably undemanding plants that do not require soil amendment or regular watering. Frost sensitive plants can be moved easily to sheltered locations if contained. Flashy plants like orchids and tuberous begonias that get displayed prominently while blooming can be concealed while not so impressive.

Of course there are many pendulous plants like Boston fern, spider plant, string or pearls and burro’s tail that really are at their best in hanging pots. It is also hard to deny that there are all sorts of artsy containers, like colorfully glazed pots and sculptural concrete urns, which are appealing enough to justify growing plants in them, even if just to show off the fun containers. Bonsai requires containers, but that is another big topic!

Cyclamen

Autumn is not far behind cyclamen.

The advantage of cyclamen, Cyclamen persicum, is nonconformity. Bloom begins in autumn when there are not many other flowers to provide color, and continues until spring. Cyclamen then defoliate and go dormant through summer while most other plants enjoy the warm weather. Even their red, pink, white, purple or salmon flowers are inside out, with petals flared back. The flowers can stand as high as six inches, just above the somewhat rubbery foliage. The rounded leaves are mostly dark green with silvery or gray marbling

If used as annuals for one season, cyclamen are uniform enough for bedding. However, if later overplanted with warm season annuals and allowed to stay through summer dormancy, regeneration the following season is variable, with larger and smaller plants, and some that do not survive. As perennials, cyclamen therefore work best in mixed plantings, where variety is not a problem. Cyclamen should be planted with their tubers about halfway above the soil level, and should not be mulched. Soil should be rich and drain well.

Japanese Aralia

The bold foliage of Japanese aralia is quite striking, whether kept low and dense, or suspended on taller lanky stems.

It may not grow too rapidly, but Japanese aralia eventually gets nearly eight feet high and wide, and commands a bold presence. The deeply and symmetrically lobed leaves can get as broad as a foot and a half, on long petioles (stalks). The foliage of ‘Vairegata’ emerges with a yellow border that turns pale white. ‘Moseri’ stays quite compact.

Plants grown for their foliage can be maintained by cutting the oldest stems to the ground as they begin to deteriorate, so that newer stems can replace them. Alternatively, lower growth can be pruned away as it develops to elevate the canopy and expose interior stems. However, individual stems do not last indefinitely, and will eventually need to be replaced by any convenient watersprouts.

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.

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.

Drought Tolerance Versus Container Gardening

Drought tolerant plants loathe root confinement.

There are probably just as many reasons to not grow plants in containers as there are reasons to justify container gardening. Some potted plants consume less water than they would in the ground, but only because their demand is proportionate to their limited size. They only want more water in the ground because they can grow larger.

The most drought tolerant of plants are actually the least practical for pots or even large containers. They tolerate drought because they efficiently disperse their roots so extensively. Since they can not adequately disperse their roots in pots, they rely on what they can get from a relatively limited volume of soil. However, even if watered generously, many drought tolerant plants simply can not produce enough finely textured roots to absorb enough moisture.

For example, eucalyptus trees want to begin dispersing their roots while very young. If confined, their long and wiry roots simply go around within their limited volume of soil, trying to find a way out. They can develop a few more fibrous roots than they typically would, but probably not enough to compensate for limited root dispersion.

Wild lilac (Ceanothus spp.), flannel bush, manzanita and smoke tree are not only sensitive to confinement, but have difficulty recovering from confinement if put into the ground after their roots have circled too much within a container. Pines and many other conifers are likewise sensitive to confinement, but some types can recover if the binding roots get severed before they go into the ground.

Plants with dense and fibrous roots are more adaptable to containers. Most succulents and common yucca are good choices. Ferns and some grasses also work nicely, but need to be watered rather regularly. Some types of arborvitae and juniper work better than larger coniferous evergreens. Some small bamboos can stay potted, but not larger types.

Annuals, compact perennials and many ground covers that provide color and fill in space around larger plants are naturally adaptable to container gardening, but their need for regular watering can not be denied. There simply is no practical way of combining container gardening and drought tolerance.