If only these houseplants could talk.
It’s easy to imagine they’d be screaming their indignation at the wintertime perches we’ve assigned them — places of painfully low light near some drafty window — in the inhospitable arid zone that is indoor heating season.
“Enough, I’m begging you!” And: “Get me out of here!”
But they don’t scream, except maybe through body language, dropping leaves or looking crispy to tell us that this just isn’t working for them.
Houseplants don’t read, either, as Karl Gercens, the conservatory manager at Longwood Gardens in Kennett Square, Pa., is quick to point out. That’s our job.
It’s up to prospective plant parents, he said, to identify houseplants “that will thrive, not just survive” under our particular conditions.
That doesn’t just mean learning textbook protocols by rote. It means learning to read the plants, too: watching for trouble signs — the way the leaves of a spider plant (Chlorophytum comosum) will turn a shade of gray, for example, when a drink is required — and figuring out how to get ahead of them.
Rather than inviting another winter of their discontent, Mr. Gercens challenges us to rethink which houseplants we grow and how we care for them.
In the case of this self-described “rule-breaker” — he has been a houseplant person since he was 5, when his family inherited Great Grandma’s collection — that doesn’t always mean using the gentlest hand. When some plants grow leggy or weak, he’ll deliver hard cutbacks.
And he advises that we get braver about repotting, as well — not just up to roomier quarters, but sometimes down.
Where he never applies tough love: by forcing a plant to grow where it doesn’t belong.
The two-acre conservatory at Longwood Gardens, with its ample light and climate-controlled environment, can support most anything. At his home, as in ours, the conditions are less ideal.
Success hinges on an honest assessment of your light and humidity conditions, and matching plant to place.
“Face it: If you only have north-facing windows, there are just a certain number of plants that will work,” Mr. Gercens said.
Don’t set your sights on orchids (or if you do, invest in grow lights). The corn plant (Dracaena fragrans) or peace lily (Spathiphyllum) are better candidates. In low humidity, he recommends stalwarts like the snake plant (Sansevieria) or cast-iron plant (Aspidistra elatior).
But even when selecting for durability, don’t take dull for an answer. As he put it, “You don’t have to just have a plain-Jane green plant.”
Look past generic choices and search out White Aspen, a corn plant cultivar with striking white margins, or Sweet Pablo peace lily, which blooms more heavily than some. Other options include the Black Gold snake plant, which has leaves edged in yellow, and Snow Cap aspidistra, whose foliage is flushed with white.
That’s where he wants to steer us: to workhorse plants that match our conditions, yes, but in their most exciting incarnations.
Like Your Favorite Shirt, but in Unexpected Colors
In 25 years of working in the Longwood conservatory, Mr. Gercens estimates that he has witnessed more than a million display plants move through the galleries, as the team mounts shows like the current “Winter Wonder” (through Mar. 26).
But that parade of plants, including many rarities, hasn’t tarnished his lifelong affection for one of the most common, easiest houseplants, the upright-growing rubber tree (Ficus elastica), with its broad, glossy leaves. His choice: the cultivar Ruby, whose red new growth and variegation form a mosaic of salmon, sage, red, gray and green.
“It makes me chuckle that for so many years, I was happy with just a green plant,” he said. “It’s like you were happy wearing a burlap bag and calling that an outfit, but now you’ve got cashmere and you just didn’t know how good it could be.”
Anticipating any plant-snob pushback, he added: “You might think, ‘Ugh, I’ve done Ficus.’ Have you done all the Ficus, though? I don’t know if it’s me and my lack of fashion sense, but I find a shirt that I like, I get multiple colors. It works for me. The same I think is true with plants.”
Consider holiday cactus (Schlumbergera). Before you say “boring,” visualize a variegated selection with butter-yellow-splashed foliage. Mr. Gercens got cuttings of Norris Variegated five years ago from a collector in Maine, and rooted them.
Start your own quest the way he does, by searching social media for the genus you’re after and then networking with its fans.
Another startling twist on the familiar is a variegated form of foxtail asparagus fern (Asparagus densiflorus Myersii). It has the characteristic “tactile, firework-y plumes,” but its new foliage starts out stark white. Mr. Gercens first saw one at the Philadelphia Flower Show maybe 15 years ago, and finally scored a piece big enough to fill a four-inch pot eight years ago.
Now it’s in a container many times that size — but he chose one with a crack, so he won’t mind losing it. The asparagus fern’s thick roots swell according to how much water it gets; a tight fit can suddenly become too tight.
“Never put them in a container you love, because they will blow that pot up,” Mr. Gercens warned.
A ‘ZZ Plant’ of a Different Color
One of the breakout plants of the internet houseplant craze has been Zamioculcas zamiifolia, known as the “ZZ plant.” This aroid family member withstands low light and low humidity, and is among the toughest of the tough.
But even with a relatively “new” species — Zamioculcas made its way into the trade only in the 1990s — Mr. Gercens touts an improved version, called Raven or Dowon, whose young green foliage ages to purplish black.
Recounting stories of past fads, like the Victorian orchidomania, when the latest plants were for the wealthy only, he mused about how high-tech propagation methods have changed that for many plants, including Raven.
“It is unusual, but I’m not going to call it rare,” he said. “It could have been rare, but it has been propagated to the point that really anybody can have one. Never has such an unusual plant been available to everyone at one time.”
The Basics: Soil, Water, Fertilizer — and a Good Rinse
Those of us who want improved results need to get our houseplant basics down.
First assignments: “Finding a trusted potting mix,” Mr. Gercens said, and checking your water source.
Not all bagged soil is created equal. A good growing medium is light and fluffy, not dense; try squeezing the bag for an indication of its texture.
Then do some amending. Mix that potting soil with as much as 50 percent of an even more porous material, he suggested, like bagged orchid bark or a potting soil labeled for orchids, to achieve the improved air circulation that roots are happiest in.
Next: What are you watering with? Tap water that has been softened for household use is not suitable for plants, as it often contains excess salts. If you have a softener, use water from a tap that doesn’t flow through the device.
The best choice, Mr. Gercens said, is rainwater. That gives you another reason to set up a rain barrel (or at least set out a bucket).
Whatever the source, deliver water to plants at room temperature, not cold.
Mr. Gercens advises doing a small amount of fertilizing year-round — a tactic often called “weekly, weakly” — to promote consistent growth. Apply a liquid feed at half the strength recommended on the label. Fertilizer can be another source of harmful salt buildup, though, so remember to flush out the pots periodically.
“We are all fearful of water escaping the tray and getting onto the floor or carpet,” Mr. Gercens said, “so we just give them a little bit of water each time. We really never leach the soil of all those excess salts.”
He is the kind of dinner guest who will scan your terra-cotta pots for signs of crusty buildup. If it’s present, he’ll tell you how to correct it, and how to clean photosynthesis-inhibiting grime off the foliage: Everybody into the shower for a good rinse.
Downsizing: Stern Cutbacks and Smaller Quarters
Struggling plants, or those that have outgrown the space or pots you can accommodate, should be slated for pruning, repotting or both in early spring, “as growth is beginning,” Mr. Gercens said. “You want plants to be on the upswing when doing that.”
Are some too tall, stretched out or straggly? A hard cutback near the base can rejuvenate many, including Pothos (Epipremnum), various Ficus, spineless yucca (Yucca elephantipes), Schefflera and corn plant. But go carefully: Palms and cycads won’t rebound.
With succulents, including Schlumbergera and jade plant (Crassula ovata), tip pruning is recommended. Let the cuttings sit a few days so the ends form a callous and then root them, yielding fresh new plants.
When to pot up to bigger quarters is probably obvious, but plants displaying weak growth may actually need a smaller pot to thrive. “A too-large pot can hold onto unnecessary moisture and cause root rot,” Mr. Gercens said.
In that case, unpot the plant, tease the excess soil off the roots, and then prune them a bit before replanting the vigorous divisions in a pot, or pots, of fresh soil. “So many times people are afraid to cut the roots,” he said.
But as with his plant choices, he’s clear on this: Go ahead and dare.
Margaret Roach is the creator of the website and podcast A Way to Garden, and a book of the same name.
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