Grow Asparagus—The Perennial Vegetable!
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Question. I planted asparagus in a raised bed two years ago. I did not harvest the first year, have lots of ferns still standing, and hope to enjoy my first spears this spring. Do I need to do anything special to the plants? And what should I do over the winter?
---Tuna Bob in West Chester, PA
Hi Mike! I would like some tips on planting an asparagus bed this spring. Hope I am not too late. Is it OK to use corn gluten when I plant to prevent weed seeds from growing? I would like suggestions on amending the soil as well; should I use composted horse manure? And I'm told my soil is acidic. Should I lime to make it more alkaline?
---Michele in Locust Grove, VA
Answer. It's not too late at all, Michele! One of the firm rules of gardening is that you shouldn't work wet soil, and your Washington, DC area had a very wet winter; so you might actually need to cool your heels a bit. Some people even wait until the end of summer to plant, when the soil is generally drier and easier to work. (The asparagus doesn't care; Spring or Fall, its all the same to the spears.)
Completely composted horse manure—no heat, no odor—is one of the classic components of an asparagus bed. However, recent findings indicate that asparagus actually craves potassium and phosphorus as much as nitrogen, so feel free to substitute high-quality compost for the manure. No matter what, sprinkle liberal amounts of rock phosphate or bone meal in at planting time. And asparagus thrives all the way from an acidic 6 to a neutral 7; so if your soil's pH tests in or near that range, leave it alone
Most important is to begin with a bed that drains exceptionally well and is filled with rich organic matter. So remove all the soil down to a foot deep and use a garden fork or pry bar to bust up the bottom of the bed for drainage. Then fill it about half way back up with a mixture of the best of the excavated soil—no big clumps of clay—and compost or composted manure.
Mix the rock phosphate or bone meal in and lay your crowns on top of the amended soil. The crowns look like octopuses; if they're dry, soak them in water for an hour before planting. Then cover them with a few inches of organic matter and soil, but not all the way to the top. Fill the rest in gradually over the course of the season until the bed is level with the surrounding soil. Trust me on this one.
Oh and yes, feel free to dust a little corn gluten every time you add soil to prevent weed growth; weeds are this tasty treats' biggest foe.
Neither of you should harvest any spears the first year. Let them all blossom into those lovely asparagus fronds. Gardeners in the South can harvest some spears the first year without decreasing yields; the warmer the clime, the safer this is. If in doubt don't. Harvesting first year spears in the North can cut future production almost in half.
Mulch the bed in the Fall—and every fall—with compost, straw or well-shredded leaves; no wood mulch! Everyone can harvest a few spears the second year. But the further North you are, the more cowardly you should be; the more discipline you have early on, the better the patch will produce over the next couple decades. No matter where you are, only pick spears for the first two weeks that second year. Snap the stalks off to harvest. If you use a knife, be sure not to cut into the roots. From year three on, see below:
Question. I put an asparagus bed in about 6 years ago (two rows of five crowns each) and am having trouble finding reliable harvest and growing info. I let the ferns stand over the winter, clear them out in late winter or early spring, then feed the patch with compost or leaf mulch. I get asparagus, but only a few at a time; not really enough for a single meal. I'm also curious as to why sometimes I get a mixture of fat and skinny stalks. And how long IS the season for fresh asparagus in this area?
- ---Jennifer in Allentown, NJ
You also need to change your feeding schedule and fertilize right after you finish picking in the summer; Spring is way too late. Try dusting some rock phosphate on the bed after this year's harvest, cover that with some aged horse manure; and then mulch the bed with compost in the Fall.
Harvest typically lasts four to eight weeks in Spring, and often includes spears of varying thicknesses. Pick by height; eight inches is the recommendation. Stop harvesting when you no longer get ANY thick spears, and let that last run turn into those beautiful fronds.
If you have problems with aphids or asparagus beetles, cut the fronds off after a couple of hard frosts, clean out any old mulch and put fresh mulch down for the winter. If you don't have serious pest problems, let the fronds stand until late winter or early spring.
Question. Mike: Did I hear you suggest putting salt on established asparagus beds? Should I do this? Thank you!
---Suze in the mountains of rural western NC
Answer. Sprinkling some rock salt on the bed in winter often increases your yield, and it definitely helps suppress fusarium root rot. But it also sends earthworms and other soil life packing. If yields are good and plants are healthy, I would not salt. But I would also not hesitate to sprinkle a bit around if I had disease or yield issues.