The iron cross begonia (Begonia masoniana), is one of the most charismatic pieces of greenery out there. This plant store money maker has small spikes that grow from its stem and leaves, giving it the texture of a wirehaired terrier. The stem and leaf lining are red, and there’s a black spot in the middle of each leaf that I would describe more as a Bat-Signal than an iron cross.
This summer, on the first day that reached above 90 degrees Fahrenheit, three of my iron cross begonia’s largest leaves grew brown patches and died over the next few days. Turns out that the sweat-inducing extremes we experience in the middle of the year are not only annoying to us, but can negatively affect plants. That includes the summer heat, and the artificial cold blast of your trusty air conditioning unit.
Study the evolutionary history of your plant
Knowing where your plant came from and what its natural habitat is like will give you a good hint about how well it adapts to summer conditions wherever you are.
My iron cross begonia likes high humidity, but if any dewdrops gather on the leaves, they will rot and die. That’s because this plant is from northern Vietnam and southern China, where the breeze will usually drive away any excess water from the surface of the foliage.In practice, this means that I have to carefully pour water around the leaves and stem to prevent any of it from touching the plant directly. The temperature in the iron cross begonia’s native habitat usually doesn’t go above 90 degrees, which is probably why the leaves in mine burned like hands on a stove.
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The popular Pilea peperomioides, also known as Chinese money plant, evolved to grow on rocks, so it might be more understanding of a missed watering day or the dryness of your air-conditioned apartment. Pothos varieties are invasive species in many parts of the world, taking over your heart and all possible soil real estate as quickly as possible—especially in humid environments.
Rick Schoellhorn, former horticultural professor at the University of Florida and member of the American Begonia Society, suggested I pursue easier houseplants. “You have picked the begonia that I would rate as being one of the expert or advanced begonias to try and grow,” he says.
I moved from San Francisco to Brooklyn last year, and my plants have had a difficult time adjusting, I explained. Since the climate is no longer on my side, and there’s no way I’m giving up my begonia, I have to step up my artificial strategies.
Do a threat analysis
Most plants spend the winter dormant and begin to grow in the spring. By this point, they may be low on basic nutrients, suffocating in a year’s worth of salts and minerals from tap water, or their roots may have reached the limits of their pots. That’s why it’s a good idea to replant and fertilize your green housemates in early springtime, though late is better than never.
Cold blasts can also be a problem if your plant thrives in tropical weather, so make sure to keep it away from any air conditioning vents. Also, a window unit might require some sill Tetris. When finding a new location for your leafy companions, try to find a place where they get as much light as they did before. If you can’t, consider a grow light. This tool can also help if the angle of the sun coming through your window has changed and you’re not getting as much direct light as you used to.
Just like heaters in the winter, air conditioning makes the air drier, which is unfortunate since most plants prefer more humid lodgings. You can soothe the quickly crisping leaves by misting water on them, but there’s only so much you can spray and there’s controversy over whether this technique actually improves humidity. A less involved solution is to put a plate of water under your plants, maybe with some rocks. But that method can let most of the evaporate spread all over the room, not necessarily right where your plants are. That’s why Schoellhorn recommends a terrarium.
Surround your plant in glass
A glass container, Schoellhorn suggested, could stabilize the temperature and humidity of my plant while still letting in light.
This isn’t a new idea. The Wardian case is a type of enclosure made of wood and glass that allowed plant transportation across oceans in the mid-1800s. Anyone can replicate a Wardian case in their homes—you can place a glass bell jar over your plant, or get a roomier solution with a glass terrarium.
And if a fancy glass terrarium is too expensive, Schoellhorn has a more frugal suggestion. “Find the clear salad bowls, and take one and invert it on top of the other,” he says. If you find that two same-sized bowls are unstable, you can get a slightly smaller one and put it over a large one to prevent top-heaviness.
If you want a bigger humid environment for your plants, you can also find other solutions. There’s a whole corner of social media, including multiple videos on YouTube and TikTok, and even an entire Instagram account, devoted to turning Ikea cabinets into indoor greenhouses. Schoellhorn added that even clear and semi-clear plastic containers can work in a pinch for plants that don’t mind the plastic-dappled light.
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If you get tired of the maintenance work, don’t be afraid to throw in the towel. You can donate your plant to friends, Craigslist’s free page, your local Facebook buy-nothing group, or a plant shop in your area.
Then you can get a plant that’s easier to take care of in your weather conditions. Your local nursery will have recommendations. “For a lot of people, the whole beauty of the houseplant is ‘I’ve had that thing for 10 years and I’ve never repotted it, I’ve never done anything to it, and look, it still looks nice,’” says Schoellhorn. “I mean, that’s success.”
