How to grow 3 perennial edibles

When you're considering edibles to add to your garden, choose a few perennials, like asparagus, Jerusalem artichokes and rhubarb, that will come back year after year.

Despite what you've heard, you don't have to wait until the third year to pick asparagus.

• Begin harvesting a few spears the second year during the month before your last spring frost. Each season, harvest all of the spears that emerge early, because they will probably be frozen back anyway.
• Once your patch is three or more years old, harvest for six weeks every spring, or until the average size of the spears declines to the diameter of a pencil.

Grow an all-male asparagus plot

• Older open-pollinated strains, such as 'Martha Washington', include both male and female plants, but all-male hybrids grow faster and bear much bigger spears.
• To make sure your plants are male, use 'Jersey Giant', 'Jersey General', 'Jersey Knight', or other all-male Jersey hybrids. Another reliable hybrid is the productive 'UC 157'.

Be sure to plant plenty

• Put in about 25 asparagus roots for each member of your family — more if you want to freeze some for later. To set out 50 plants, use a nine-metre double row, one metre wide.
• Beyond attentive weeding for two years, an asparagus plot needs little attention to produce well for 10 to 20 years.

Give the plants a soft blanket

• Mulch your asparagus bed every fall and spring to maintain a continuous 10- to 15-centimetre cover of compost and rotted manure.
• Not only will you keep weeds away and conserve moisture, but you'll build a compost pile right on top of the dormant crowns, assuring your crop a long, productive life.
• Don't use sawdust or bark; both are too acidic for asparagus.

Jerusalem artichokes — also called sunchokes — aren't artichokes at all, but rather native perennial sunflowers.

• Even though you will dig up most of the roots every fall, a few will slip by you and grow into new plants the next spring, so plant them behind asparagus, which often stays put for decades.

Use them as flowering screens

• In rich soil and partial shade, Jerusalem artichokes can grow two to four metres tall. Pick a spot where they shade other plants.
• With their head-high yellow flowers, they make a good screen for compost heaps or other unsightly areas.

Watch out for problems

• Dig all the roots you can find in fall until the ground freezes and then again in spring as soon as the soil has thawed.
• In a heavily mulched bed, the tubers can even be dug from underneath a blanket of winter snow.
• Plots left undug can grow so well that the plants become invasive.

A rare vegetable perennial well suited to cool climates, rhubarb plants live for a long time. A well-tended rhubarb plant, started from seed or a root crown, can be harvested from for decades.

• 'MacDonald' has bright red stalks and excellent flavour, while 'Starkrimson' is less acidic and prized for its sweetness and deep red colour.

When to harvest rhubarb

• Rhubarb stalks are ready to pull when they are 30 to 45 centimetres long. The newly developing stalks of the deepest red usually have the best flavour.
• Pulling season is over when emerging stalks stay small.

Spare the knife

When harvesting, never cut a rhubarb stalk off the plant, or the remaining stub will bleed and invite rot.

• Instead, hold the stalk near the base and give it a slight twist as you pull it away.