A Seattle gardener shares his culture tips for growing tropical plants.
If exotic plants tickle your fancy, you're probably keenly aware of all the sub-tropical plants available at nurseries and garden centers these days. Heat-loving plants are becoming focal points in backyards everywhere — even in places you might not expect them. Take Seattle, for example. In the heart of the Pacific Northwest, this city receives about 150 days of rain each year, and while that sounds tropical, the temperature doesn't get hot enough to grow tropical vegetation.
"Here I am in Seattle, surrounded by houses," says tropical plant expert Jeff Hedgepeth, "but when I walk in my tropical garden, I feel like I'm somewhere. According to master gardener Paul James, the real magic in this garden is the tropical feel that Hedgepeth has created by combining lots of plants, including a few Fahrenheit-finicky tropicals.
Hardy plants such as English laurel, or Prunus laurocerasus, golden hops (Humulus lupulus), assorted clematis and an Asian pear tree tolerate Seattle's cooler temperatures and make up what Hedgepeth calls the backbone of the garden. Ideal backbone plants include low-maintenance plants that drape the yard in foliage and fill every space, leaving not a bare spot of earth.
"I then look for the true tropicals that really add zing to the garden," he says. "My favorite is Canna 'Tropicana'. Who couldn't love a plant that has green-, orange-, brown- and yellow-striped leaves?"
Cannas and bananas surround the cabana and set the mood. "Believe it or not," says James, "these true tropicals grow very well anywhere the climate is moderate to warm, like summers in Seattle. But as the mercury drops, so will these special plants, if they don't get some special care."
Generally, if you're going to leave plants in the ground, you're not going to be able to protect the plant more than maybe one or two climate zones beyond the one you live in. This Australian tree fern, or Cyathea australis stays in the ground with a little over-winter help.
To provide some protection, Hedgepeth builds a simple cloche using bamboo poles for structure, plastic sheeting for insulation and clips to secure the sheeting in place. This structure will buy 5+ degrees of frost protection. "If I hear that we're going to have a serious cold spell, I'll often come out and plug in a little heat lamp as an extra source of heat just to raise the temperature a degree or two," says Hedgepeth.
The general cold-weather rule for tropicals and subtropicals is acclimate or hibernate. Tender cannas need more warmth in the winter than a cloche provides, so for them, it's time to come in from the cold. After the first frost, when the tops have been knocked to the ground, Hedgepeth digs up his cannas. What you get is a root ball that looks like this.
After cleaning off as much soil as possible from the root ball, Hedgepeth washes it with a hose, dries it for a few days, then wraps it in newspaper before storing it in a cool, dry place for the winter. The same procedure goes for the banana. The idea is to put the plant into dormancy during the cold winter.
Protecting tender subtropicals can also be as easy as bringing potted plants indoors or snuggling them up to the house. According to Hedgepeth, the best part is that it only takes a day to put his garden to bed in the winter and a day to bring it back out in the spring. "It really isn't that much work, and you just get such cool plants if you take the time," says Hedgepeth.
While it may never get warm enough in Seattle for some of the more exotic plants to fruit, a tropical flavor permeates the yard in other ways. Take this empress tree or Paulownia tomentosa, which grows so well that pruning is necessary to keep it in check. And even pruning has its advantages.
When pruned, the tree produces large, lush, tropical leaves compared to the small contrasting leaf size of the same tree left unpruned. There's no cutting back on the beauty of Hedgepeth's garden. By combining hardy plants with heat-loving plants, the tropics feel right at home even this far north of the equator.