How to grow edible perennials

(Chelsea Conrad/Washington Post illustration)
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My backyard is a graveyard, littered with the sad reminders of failed edible perennials. There’s a forlorn square along the western fence that was an attempt at a strawberry bed. A few feet away lies a bit of dead space where I failed to cultivate a rhubarb patch. Out front by our stone walkway languishes a bit of sunny side yard I thought would be the perfect spot for a raspberry bramble. I was wrong.

These plants are supposed to be set-it-and-forget-it types — easy to maintain and everbearing. Although I have a green thumb when it comes to my vegetable and herb gardens, edible perennials are clearly my weak spot. My disappointment runs deep. I have a vision of a yard ringed with dependable producers, reliable sources of fruits and vegetables throughout the year to help keep my cooking fresh and interesting.

Determined to finally bring my dream into fruition, I turned to four gardening experts to get their insights into what options are best for the DC region, and growing tips to ensure success. Armed with this knowledge, I plan to turn my backyard graveyard into a lively collection of edible perennials — and you can, too.

“When the zombie apocalypse comes, this is going to be the most reliable vegetable in your garden,” says Kathy Jentz, editor of Washington Gardener magazine.

The tubers produce prolifically, which is both a pro and a con. Left to their own devices, sunchokes can take over your garden. To avoid this, plant them in a separate bed, preferably away from your others, perhaps along a property line. Along the edges of the bed, insert a root barrier into the ground extending three feet deep. The location receiving full sun is best. Unless there are drought-like conditions, no watering is required. Plan on harvesting in October, then covering the patch with mulch or hay for the winter.

“Just put it in the ground and get out of the way,” says Lincoln Smith, founder of Forested, a forest garden design company. “It’s a perennial for dummies.”

Plant horseradish roots in a location receiving full sun. They should be in a separate bed; the fiery herb will run rampant and take over whatever else is growing nearby. Get the ground ready for planting by tilling up the earth about 10 inches deep, removing rocks and mixing in compost. Horseradish root can be harvested throughout the year, except when the ground is frozen.

If you have a sweet tooth and don’t want to do a lot of work, raspberries are a surefire bet, says Meredith Sheperd, founder of Love & Carrots, a garden design and installation company. “They self-pollinate, they produce the first year, and they produce densely.”

Choose a 3-by-10-foot section of your yard that receives at least four to five hours of sun a day, although six to eight hours is ideal. (My own raspberries failed because they didn’t have enough room or light.) The brambles will naturally fill up the space over time without any extra attention. Expect to harvest them throughout the summer. Generally, raspberries are very low-maintenance; just cut them back in the fall.

To succeed with these succulent berries, find a spot in your yard that gets at least eight hours of sun a day. Then consider how much room you can devote to them. “Strawberry beds are taking off,” says Dominique Charles, founder of Plots and Pans, which specializes in edible gardens and landscapes. “So you need a lot of space or a way to contain them, such as raised beds, stackable strawberry planters or root pouches.”

After planting, she fertilizes strawberries with earthworm casings to encourage a hearty harvest, which happens sometime between mid-May to July, depending on the varietal. Water your bed daily until after you’ve gotten all the fruit for the season. Cover the bed with straw for the winter. In spring, once the patch starts growing again, Charles recommends clipping any dead brown matter.

The verdant spring favorite requires patience in the beginning. You won’t harvest any for at least a year, probably two, if you plant mature asparagus roots, known as crowns. (It’ll be three years before a harvest if you plant seeds.) “But then they’re set it and forget it,” Charles says. “All you have to do is weed them and eat them.”

For optimal growth, asparagus requires at least eight hours a day of sunlight. Generally, asparagus can be sown directly into the ground; no raised bed is required unless you have extremely acidic soil. Simply dig a six-inch trench and lay the crowns at the bottom. Don’t crowd the bed. Leave 18 inches between each crown and a foot between each row. Water asparagus daily, but don’t overwater, which can rot the roots and destroy your bed.

The vegetable that most people think is a fruit isn’t a slam dunk in this region, which is often too hot. However, some gardeners do experience serious success, reaping plenty of stalks for pies, crumbles, jams and more. Consider rhubarb one of those plants that require a little luck to flourish. For the best chance of success, place a few roots in a six-foot square plot that gets a full day’s worth of sun. Over time, the plants will divide and fill the area. They require little maintenance; just keep them weeded and lightly fertilize them in spring.

Rhubarb is also the waiting game. “I wouldn’t touch it the first year. The second year you might be able to harvest a few stalks,” Sheperd says. “The third year you should be good to go with a full harvest from late spring until later in the summer.”

Unless you have a large yard with lots of extra space, dwarf highbush blueberry plants are best, because they grow about one to two feet high and equally wide. Many are bred for container gardening, making them ideal for patios and porches. You’ll need at least two plants, so they can cross-pollinate, although more is recommended to guarantee a sizable berry yield. Plan on harvesting blueberries later in summer, usually July and August. To ensure you don’t lose too many berries to neighborhood critters, cover the plants with netting. “But check the netting every morning and evening to make sure a little songbird or snake didn’t get snarled in it,” Jentz says.

Before winter, mulch the bushes. At some point during the cold-weather months, prune them to remove dead and damaged branches. When spring arrives, use a fertilizer designed for acid-loving plants.

Martell is a writer based in Silver Spring, Md. His website is also nevinmartell.com. Find him on Twitter and Instagram: @nevinmartell.