Ponytail Palm

In its native ecosystem, ponytail palm grows as a small tree.

Some succulent plants and their friends do not mind being grown as houseplants. Ponytail palm, Beaucarnea recurvata, is one of those rare friends of succulents that actually prefers to be inside, at least during winter when they can be damaged by cool weather and moisture. Plants that are houseplants through winter and get moved out to the garden through summer should be protected from harsh direct exposure since their foliage is adapted to the home environment. Otherwise, ponytail palm likes the sunniest rooms in the house.

The weird distended caudex at the base of the stem is the most distinctive feature of the ponytail palm, which as actually neither a palm, nor outfitted with ponytails. However, almost like a palm, pruning a solitary top down will likely be fatal. (Pruning the terminal bud off the top of a palm will necessarily be fatal to the affected trunk.) Unlike (solitary) palms, ponytail palm can eventually develop multiple trunks, which can be pruned off if absolutely necessary.

In their natural environment, ponytail palms can get to be shade trees with sparse limbs terminating with tufts of narrow strap shaped leaves. Yet, as slowly growing houseplants confined to containers, they rarely get more than six feet tall after many years. They really need good drainage, and prefer to be watered only about twice to four times monthly.

Rubber Tree

Big glossy leaves of the familiar rubber tree like a sunny spot in the home, away from sources of heat.

Pruning a rubber tree, Ficus elastica, in the home takes a bit of acrobatics, since any wound immediately bleeds staining white latex. While pruning with one hand, the other hand must catch the latex with a rag. A third hand is needed to catch the bleeding piece of stem that gets pruned away. To make things more complicated, all three hands should avoid the potentially caustic latex. Even if it is harmless to the skin, it is a painful irritant if it gets into the eyes.

Young trees have larger glossy leaves that may be as long as a foot and half as broad, although most are about half as long and broad. Many modern cultivars have variegated or bronzy foliage. Where it gets enough sunlight as a houseplant, rubber tree will eventually need to be pruned for confinement. After all, in the wild, it can get more than a hundred feet tall and almost two hundred feet tall, with trunks more than six feet wide! In the garden, it needs shelter from frost. Aerial roots can develop in humid environments.

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.

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.

Boston Fern

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This fern is nowhere near Boston.

It is not actually from Boston. The first Boston fern, Nephrolepis exaltata ‘Bostoniensis’ was merely discovered in Boston, as a mutant in a shipment of otherwise normal ferns. Unlike the more upright parent plants, Boston fern has softly arching fronds that can hang vertically at the ends.

The fronds are typically about a foot and a half long, and can be a few feet long in humid and partly shady environments. Each frond is comprised of many pinnae that are neatly arranged on both sides of a wiry rachis (leaf stalk). Each leaflet is an inch or two long or longer. Delicate aerial roots sometimes dangle below the foliage.

Through the 1970’s, Boston fern was one of the most popular houseplants. Yet, it really prefers more humidity than it gets inside. It is actually happier on porches or in atriums where it is sheltered from frost and harsh sun exposure. It prefers partial shade outside, but likes abundant ambient sunlight as a houseplant.

Ornamental Pepper

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Colorful but not flavorful ornamental pepper.

The red, orange, yellow, purple, white or almost black fruit of ornamental pepper that naturally develops in summer can be seen at any time of year because the plants are grown in artificial greenhouse environments. The peppers are usually small and narrow, and stand upright above their glossy rich green foliage. Some are narrower. Others are a plumper. Technically, the fruit is edible, but it is not as flavorful as peppers grown for culinary purposes.

Because the plants are sensitive to frost, they are more often grown as houseplants than out in the garden. In the garden, they need shelter to survive as perennials. As houseplants, they need warm and sunny exposure in order to bloom and develop fruit. They should be watered regularly, but only as their potting soil is starting to get dry.

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Look but do not bother tasting.

Tropical Plants Far From Home

P80811+++++Plants can inhabit nearly every climate on Earth. They live in hot and dry deserts, cold arctic regions, rainforests and just about everywhere in between. Plants seem to have it all figured out. Some even know how to live in our homes as houseplants, although they probably did not plan it that way. Most houseplants are tropical plants that are naturally endemic to tropical ecosystems.

It is actually their tropical heritage that makes them more comfortable in our homes. Tropical climates tend to be conducive to proliferation of all kinds of plants. Those that want to live there must be competitive. Trees compete by growing faster and taller than other trees. Vines compete by climbing the trees. Understory plants that live under taller plants compete by needing less sunlight.

It is these understory plants that do not mind the shade of our homes. Even those that like bright ambient light might never expect to get direct sun exposure. The various ficus trees that might naturally grow tall enough to reach the top of a forest canopy in the wild are still understory plants while young. Because they know how to use resources efficiently, tropical plants do well in pots.

However, these advantages are not so useful out in the garden. Tolerance to partial shade also means that some tropical understory plants need to be sheltered. If too exposed, foliage can get roasted by sunlight or arid wind. (Most tropical climates are more humid than local climates are.) Complaisant roots do not disperse well enough to sustain lush foliage without regular watering.

Ironically, roots of the various ficus trees are very aggressive because they to not disperse deeply, but instead spread out at the surface of the soil where they grow into exposed root buttresses.

The most familiar weakness of tropical plants is their susceptibility to frost. Even though it does not get very cold here, it gets cool enough in winter to offend plants that would never experience cool weather in the wild. Actual frost can severely damage foliage, and can even kill some tropical plants.