No matter how early the garden is planted, the time between sowing seeds and the first harvest seems interminable. That's why I cultivate perennial edibles, many of which are ready to eat earlier in the growing season than annual crops. The rosy knobs of rhubarb, for example, push through the soil just as I'm sowing pea seeds. Like a well-synchronized orchestra, lovage and other perennial herbs emerge in tune with the asparagus, one of the first vegetables of spring. The tiny white flowers of alpine strawberries above shiny green foliage are a sign that this sweet taste of spring is near.
A wide range of perennial edibles—vegetables, herbs, and fruits—is available to the gardener. Because of their permanence, perennials benefit from careful soil preparation. But once the plants are well established in the garden, they spring to life each year, heralding good things to eat and becoming the part of the kitchen garden that never stops giving. As you plan your spring garden, consider allocating some ground to the four hardy perennial plants that follow. They are both ornamental and productive and are mainstays of my Vermont kitchen garden in USDA Plant Hardiness Zone 4.
Asparagus produces young edible shoots in the spring and is the best-known and most widely planted perennial vegetable. If managed correctly, it can provide several months of fresh eating and many years of reliable growth. For those who have seen asparagus only on their dinner plate, the tall, ferny growth of mature asparagus plants comes as a surprise.
Because asparagus will occupy its space in the garden for a long time, it makes sense to build proper soil in advance. One of asparagus's requirements is a near-neutral pH, between 6.7 and 7.0. While it will grow at lower pH, research conducted at Michigan State University shows that low soil pH is more conducive to fusarium wilt, a fungal disease. Keep the 6-foot height of the summer foliage in mind; don't plant asparagus where it will shade other crops. Choose a well-drained location in full sun.
Plant asparagus during its dormant period: early spring where winters are cold; fall or winter in milder climates. Dig a trench a foot wide and nearly as deep, incorporating plenty of compost and a handful of high-phosphate organic fertilizer. Space the crowns about 18 inches apart and cover them with 2 to 3 inches of rich soil. Add more soil as the plants grow to gradually fill the trench.
Asparagus has been a staple in vegetable gardens for centuries. 'Mary Washington' and other Washington varieties are traditional favorites, grown from seeds or crowns and including both male and female plants. Rutgers University introduced the hybrid Jersey strains, such as 'Jersey Giant', 'Jersey Knight', and 'Jersey Supreme'. These all-male hybrids are said to be more productive because none of their energy is wasted on seed formation. Some varieties produce purple spears, which turn green when cooked.
Once planted, it's best to leave asparagus for 2 or 3 years before harvesting the first spears. In the fourth spring and thereafter, the plants should be vigorous enough to yield 8 weeks of harvested spears. Charlie Nardozzi, author of Vegetable Gardening for Dummies, offers a technique, dubbed the mother stalk technique, for extending the harvest of established asparagus beds. "Instead of harvesting all the spears as they emerge from the soil, allow three large spears per crown to grow ferns," Nardozzi says. "By leaving three spears, the crown is being constantly fed through photosynthesis in the ferns. You can harvest asparagus weeks longer than normal—right into August in Zone 6." Once the diameter of the new spears becomes smaller than a pencil width, stop harvesting and allow the foliage to develop.
Asparagus is susceptible to asparagus rust, a fungal disease that is evident when yellow to orange spots appear on the foliage. Avoid it by selecting resistant varieties, such as the Washington and Jersey cultivars. Asparagus beetles can appear later in the season and will weaken the roots by defoliating the ferns. Control by hand-picking the beetles. After frost, remove and destroy the dried foliage to eliminate sites for beetles to overwinter.
From the unassuming green fronds that emerge slowly in early spring, lovage rapidly unfolds into a dramatically statuesque plant that towers above everything else in the herb garden. "Lovage lends stature to the herb garden and is extremely ornamental," says Rose Marie Nichols McGee, president of Nichols Garden Nursery, a seed and herb retailer. If planted in rich, well-drained soil, the plant can grow to 3 feet across with thick, tubular stems as tall as 7 feet. "Keep it on the edge of the garden, or it will shade surrounding plants," Nichols McGee says. She advises against growing lovage in a container, because the root system is massive.
Widely planted in Europe, lovage was originally cultivated for its aromatic roots and, to a lesser degree, its leaves and seeds. Lovage leaves impart a celery flavor with a strong hint of licorice. This distinctive taste works with tomatoes in a cold soup or blended into a cream sauce to bake over scalloped potatoes. A little lovage goes a long way, which is ironic considering the size of the plant. One plant is plenty for the average family. Rather than starting from seed, purchase a plant from an herb specialist.
Lovage is susceptible to aphids, which should be hosed off the plant promptly. Occasionally, leafminers tunnel into the foliage, causing white blotches. Remove and destroy the affected leaves.
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A true harbinger of spring, rhubarb provides thick, tart leaf stalks, or petioles, that combine well with strawberries and other fruits in jams, pies, and cakes. A single plant yields enough for a family of four and is highly ornamental, measuring 3 feet tall and wide.
It's best to purchase rhubarb crowns, rather than start from seeds, and plant them in early spring or late fall. Rhubarb cultivars vary in the color of their stalks, from red to pink to green. The deep ruby-red color is the more popular, yet the green varieties are often more productive and more tolerant of hot weather in the South and desert Southwest, where rhubarb struggles to survive.
Plant rhubarb in rich, well-drained soil in full sun or light shade, placing the crown just below the soil surface. Keep plants watered until established and during dry weather. Nourish the soil around the plants with compost in spring and fall.
Allow 2 years for new plants to establish themselves before the first harvest. Harvest by gently tugging and twisting at the base of a stalk. Discard the leaves, which are toxic, into the compost pile. Continue harvesting until the leaf stalks of new growth are slender. Remove seed stalks as soon as they appear.
Rhubarb is generally pest-free but can appeal to slugs during rainy spells. Remove the lower leaves if they harbor slugs.
Woodland strawberries, one of humankind's oldest forage foods, have become a kitchen-garden favorite. Also called alpine strawberries or fraises des bois, they are prized for the intense, sweet flavor of the petite berries. Plants remain compact, and many varieties produce no runners, a trait that makes them ideal as an edging or in a container such as a strawberry pot. Barbara Pierson, nursery manager at White Flower Farm, admits that woodland strawberries are an acquired taste. "They are not the huge, fat strawberry," Pierson says. "The small, pointed berry is very sweet, with an intense strawberry flavor that bursts on your tongue. Yet don't expect to harvest enough to make jam." What the harvest lacks in quantity it makes up for in duration, from late spring into fall.
Just a few varieties of woodland or alpine strawberries are available to the home gardener, including some with white fruits. Grow the plants from seed or, to save time, purchase virus-free plants from a nursery. Plant them in early spring in full or part sun. Woodland strawberries need only 6 hours of intense sun in order to fruit; this makes them especially good around the base of fruit trees or bordering the edge of a kitchen garden.
Prepare the soil deeply and add plenty of compost. Space plants 8 inches apart, fanning the roots in the soil and positioning the crown—the thick bit of "stem" just above the roots—at soil level. It does not take long for the plants to establish; harvest can begin the same season. Some varieties send out runners, which can be used to propagate new plants or trimmed off to divert energy to fruit production.
Woodland strawberries are generally resistant to many of the diseases and pests that afflict standard June-bearing strawberries, yet they are susceptible to slugs, whiteflies, and aphids. Maintain fertile soil and adequate space between plants to help minimize these pests.
When watering strawberries, water only the soil and not the foliage, as moisture on the leaves encourages growth of fungus.
At the end of the harvest season, top-dress the strawberry bed lightly with compost. Plan to divide crowns every third spring, or when they become clumpy. "They are tough plants, and you can rip them into pieces," Pierson says. "They are very forgiving that way."