My wife and I just finished cleaning up and mulching the asparagus beds and I thought it was a good time to talk about how we grow asparagus. It is a popular but sometimes challenging vegetable for most gardeners to grow, and we often get questions about it. Questions like “how long do you harvest?” (usually for eight weeks) or “how long has it been planted?” (since 2007).
Folks also want to know what varieties we planted. We have one row each of Jersey Giant, Jersey Knight, and Jersey Supreme. All three are hybrids developed by the Rutgers Asparagus Breeding program. I have not really seen significant differences in how the three perform here.
And how long are those rows? They are 30 feet long, and 4 feet apart. How did I plant them? After roto-tilling the soil, I dug a shallow trench about six to eight inches deep, planted the crowns with roots spread out in all directions, and then covered with a little soil. I gradually filled in the trench as the spears started coming up, and I kept them well watered during that first year.
I always tell people that if you like to eat asparagus, planting it is an investment with great returns. A well-tended bed can bear for 25 or more years. We took small harvests from ours in 2009 and 2010, and then began harvesting for eight weeks in 2011. Our total harvested from the beds is now 165 pounds, including the 35 pounds we got this year. It is safe to say the plants have paid for themselves by now – and then some!
Once the plants are established, weed management is probably the biggest challenge. This year my wife got out before the spears started emerging and cut down the dead foliage from last year. This can be done any time after the foliage is thoroughly brown and dry, from late winter until early spring. Then she weeded the beds and mulched between the rows with a layer of cardboard covered with straw. We have also used newspaper in the past, though cardboard seems to do a better job of keeping down the weeds. Our experiment with landscape cloth did not work very well, as weeds came up through it too easily and getting them out was difficult. She also likes to spread shredded paper or newspaper down the rows where the spears come up. That’s the hardest part to keep weeded.
After the eight week harvest window, we weed and mulch the beds as soon as possible, which this year was a couple of weeks ago. Then we let the new spears grow into the ferns that will grow until freezing weather arrives, replenishing the roots and crowns for next year’s crop. As you can see in the below photo, we still need to weed a bit between the rows, and then add more straw. Once the ferns fill out, the foliage will form a canopy that will shade the beds and help keep down weeds.
Another question I often get is about fertilizing asparagus, which I do once a year. The general advice is either to do it in early spring before the spears emerge, or after the harvest is finished for the year. This year I applied the fertilizer in June as we were weeding and mulching the beds. I spread it down the center of each row where the crowns are located.
And how much fertilizer do you need to use? Of course that sort of depends on the type of soil you have and its fertility. The advice I have seen, including this bulletin from the University of Missouri Extension, generally says to add between .1 and .15 pounds of nitrogen annually per 100 square feet of growing area. Since our beds are about 360 square feet that would mean between .36 and .54 actual N. Asparagus also needs moderate amounts of phosphorus and potassium for good results, and since I know our soil is low in those two nutrients, I used a fertilizer mix that supplied NPK plus I added kelp meal for its many micro-nutrients.
The only real pest problem we have had with asparagus over the years is the asparagus beetle. Both the adults and their larvae feed on the spears and ferns. They can be controlled with hand picking the adults or with a pyrethrin spray if the outbreak is really bad. But we did something different this year that really helped with that problem. In past years we harvested only spears that were larger than 1/4 inch in diameter, at least as big around as a pencil. We left the smaller spears. This year we followed advice to cut all spears regardless of size. This had the benefit of keeping down the beetles, since they had very little to feed on during the harvest season when they are typically a problem. I’ll monitor the foliage throughout the summer to make sure they don’t get out of control then.
Asparagus is a delicious and nutritious perennial vegetable, and its tender spears are often one of the first harvests each spring. If you are thinking about growing it, a little planning and annual effort can lead to a crop that will keep on feeding you for years to come. I hope you have found this information useful, and I’ll be back soon with more happenings here at HA.
For more information about growing asparagus:
Growing Asparagus In The Home Garden (OSU)
How To Grow Asparagus (Rodale’s Organic Life)
All About Growing Asparagus (Mother Earth News)
I wish I could grow it here. I’m not sure why it dies, but even if it lives the first year after a couple of years it will be dead. I’ve tried in a couple of different spots too, just in case there was something in the soil in one spot. So I will live without it sadly.
Have you ever tried mulching it with a living mulch of clover? I know there has been some research done on that. Though personally I thin living mulches are harder to weed. Real mulch is so much easier.
A white clover mulch sounds interesting. I know it works well in fruit plantings and orchards. We do have a Bermuda grass problem, and the clover in the yard is no match for it. That was one problem with the landscape cloth, since the Bermuda grass would go under it and come out the other side.
I think you answered all my questions! Wish I had 4 – 30′ rows, but I’ll have to make due with 3 small beds. I finally finished them and transplanted the seedlings a few weeks ago. Most look good (I think one died) but they are so tiny & fragile still – not even the width of a blade of grass. I’ve heard a couple of people now say that when they grew asparagus from seed, it didn’t make it through the first winter. What a disappointment that would be!
Getting the asparagus established the first year is always a challenge, even if you start with year old roots. I would mulch it good before winter and then hope for the best!
I wish I had the space to invest in a bed of asparagus. But even if I did I think the battles with the gophers would be epic. Maybe I’m better off relying on the local farmers. 🙂 Great tutorial.
We are lucky the deer don’t eat it. They actually bed down in the straw sometimes, but we’ve never seen signs of them munching on it. They do leave signs they’ve been there though!
Having never seen asparagus grow, I thought planting an open pollinated variety from seed would be a fun challenge. I chose Mary Washington and planted the seeds in the spring of last year. After life in a temporary bed, I transplanted the best looking three dozen into their permanent new raised beds this spring. The plants and roots got bigger in that first year than I had expected. So far this second spring, most look pretty good but some are just short little bushy ferns without any decent sized spears. Hopefully they’ll beef up in their third spring. Thank you for all the info. I am going to mulch this weekend. I hope to have a very small harvest next spring.
I wondered about the asparagus beetle. It is a real nuisance here and can turn the ferns into skeletons in a matter of days.
Thanks for the asparagus tutorial, I too wish I had space for a bed of asparagus, I planted 8 plants (all the space I had) last year 7 survived our severe winter, did not harvest any spears this year, hoping to get a few next year.
Your techniques are obviously working, what an amazing harvest you’ve had! I started two years ago with 12 crowns (Mary Washington). This is the first year that I really harvested anything as I didn’t want to ruin all that work by taking too much prior. But still, I only took a small amount for the first couple of weeks. I’m looking forward to when I can start the 8-week harvesting.
Dave, the Doppler radar shows some REALLY heavy rain in your neighborhood Sunday a bit after 6 pm PST. It might be 8 pm or 9 pm your time. I hope you aren’t flooded out. Please let us know how your garden fared.
Hi Lou. My weather station says “it’s raining cats and dogs”, which it is, but we’re not under water yet. The garden isn’t under water either, though I won’t have to irrigate anyways soon!
Phew! Thanks for the quick response. That was a nasty storm cell that moved through your area, and I really was worried about you. I had been watching the Spencer area, where my grandparents lived, long ago, because Spencer was under a tornado warning. When I zoomed out, I saw that your area was getting more than your fair share of rain. Wish we could have some of it. It is as hot as August here is soCal, and dry, dry, dry.
Interesting reading, My bed is 3 years old this year, I’m getting a lot of weeds, someone told me to put salt on the bed to stop the weeds, is this correct?
I would not recommend using salt in your asparagus bed. It will not only kill the weeds, it may kill the asparagus too and poison your soil for years to come. Plants can’t take too much sodium in the soil. I recommend using newspaper or cardboard sheets between rows, and shredded paper or cardboard among and around the asparagus plants. That will smother the weeds, and as it decomposes it will add organic material to the soil. I hope that helps!