Perennial Vegetables: What You Plant Once

The waiting period is real, and it is the whole decision

Perennials cost you time before they pay anything, and the wait is longer than most people expect.

Asparagus is the extreme case. You plant crowns and you do not cut a spear the first year at all. Light cutting starts in year two, and a full cutting season starts around year three. That is two seasons of watching a bed produce nothing you can eat, while weeding it.

Rhubarb is a shorter version of the same story: plant it, leave it alone the first year, take a light pull in year two, and harvest properly from year three. Horseradish is the fast one at roughly 150 days to a first root, and sunchokes give a crop the first fall.

So the honest way to think about perennials is that you are planting them for the person who lives in your house in three years. If that is you, they are among the best returns in the garden. If you are renting year to year, put the money into annuals.

• Asparagus: no harvest year one, light year two, full from year three. Then 15 to 20 years.
• Rhubarb: light harvest year two, full from year three. Then decades.
• Artichoke: about 85 days from transplant, treated as an annual in cold winters.
• Horseradish: about 150 days to first roots, and then it is permanent whether you want it or not.
• Sunchoke: crops the first fall, spreads aggressively after that.

Put them where the tiller does not go

This is the placement rule that decides whether a perennial bed survives. A perennial cannot be dug up every spring, which means it cannot live in your rotation.

Give perennials their own ground, at the edge of the garden, along a fence, or in a dedicated bed you never turn over. Anything that gets forked, tilled, or replanted annually will eventually take the crowns with it.

Height matters here too. Asparagus is short in spring and then ferns out to well over 4 feet through the summer, which is tall enough to shade whatever is behind it for the rest of the season. Artichokes get large and wide. Both belong on the north edge so their summer bulk lands on a path, not on a row of peppers.

And put them where you will walk past them. A perennial bed you cannot see is a perennial bed you do not weed, and weeds are what actually kill asparagus plantings, not winter.

How many to plant

Perennial yields per plant are low, and the counts run higher than people expect because you are harvesting a narrow window each spring rather than all season.

Asparagus gives about 0.5 lb per plant across roughly 6 weeks of cutting. That means a household wanting asparagus as a regular spring vegetable rather than a novelty needs a real bed, not three crowns. Plant 10 to 12 crowns per person if you actually like it. Spacing is 18 inches in the row with 48 inches between rows.

Rhubarb gives about 3 lb per plant, so two or three crowns cover most households and a fourth is for giving away. Give each one 36 inches, because a mature rhubarb is a big plant.

Artichokes give about 1.5 lb per plant on 36 inch spacing. Horseradish gives about 1 lb of root per plant, and one plant is genuinely enough for most kitchens for a year.

Sunchokes give about 2 lb per plant, which is the least useful number here, because the real constraint is that they spread and you will be digging them out of that area indefinitely.

The two that will take over

Horseradish and sunchokes are worth growing and worth containing, and people learn this the hard way.

Both regrow from any piece of root left in the ground, and both will be back next year no matter how carefully you think you dug them. Planting either one in the middle of a vegetable bed converts that bed into a horseradish bed over about three seasons.

The fix is to give them a spot you are willing to lose: a corner, a strip along a fence, or a large buried container with a solid bottom. Mint has the same problem for the same reason and gets the same treatment.

Sunchokes have a second issue worth knowing before you plant a lot. They contain inulin rather than starch, and a large first serving causes serious digestive upset in many people. Start with a small portion the first time.

Prepare the soil once, properly

With an annual bed a soil mistake costs you one season. With a perennial bed it costs you fifteen years, because you cannot amend deeply under a crown without digging it up.

So do the work before planting, not after. Get the weeds out, especially perennial weeds like bindweed and quackgrass, which are nearly impossible to remove later from inside an asparagus row. Work compost through the full depth. Test and correct pH now, since surface-applied lime moves down slowly.

The one test worth running first is drainage. Dig a hole about a foot deep, fill it with water, let it drain, then fill it again and see how long the second fill takes to disappear. Water still standing after a few hours means heavy, slow soil, and asparagus and rhubarb crowns both rot in ground that stays wet. Fix it with a raised bed rather than hoping.