Questions on: Asparagus

Ron Smith, Horticulturist, NDSU Extension Service

Q: Could you tell me when the best time is to plant asparagus? Do you plant it in the spring or fall? Should I use seeds or plants from a greenhouse? Any information would be appreciated. I'm sure this would be for next spring's harvest. (e-mail reference)

A: No doubt about it, crowns are the best way to go. Be sure to take the time to properly prepare the soil and you should get some spears to harvest next spring! Go to my Web site at to download "Asparagus Growing for the Home Gardener." Enjoy!

Q: Should new asparagus plants be watered or should I just let nature run its course? (e-mail reference)

A: If you are in the middle of a long, dry period, such as two weeks or more, give it a good dose of water. Sometimes Mother Nature’s course is harmful to certain plants being established.

Q: I have two rows of asparagus with annual weed (kochia, pigweed and sow thistle) problems. Is there an application that I can use to control these weeds and not harm the asparagus? In addition, my neighbor and I have beds with a prickly pear-type cactus that are infested with quack grass. Is there anything that will remove the grass without killing the cactus? (Glenburn, N.D.)

A: Try Vantage in the cactus beds. For asparagus, go to for more information. Generally, any weed control has to come before the asparagus emerges or after it is heavily frosted in the fall.

Q: I suspect I have aphids in my asparagus. How can I tell for sure? What should I spray it with and how often? (e-mail reference)

A: Aphids should be visible to the naked eye. They are very vulnerable to Insecticidal Soap, which is safe to use. Be sure to get good coverage to assure control.

Q: When is the best time to move asparagus plants? (Linton, N.D.)

A: In the spring, as soon as the soil can be worked.

Q: We are attempting to grow asparagus from seeds in our recently constructed greenhouse. We planted them in 72 plug flats in late March and transplanted into 3-inch pots in mid-May. About the time we transplanted, some of the tops started turning brown and by now almost all of them have. I'm hoping this is a case of premature dormancy. What should we do to try to save these plants? (e-mail reference)

A: It sounds like you may not have used sterilized or pasteurized soil. If you did, it may have poor drainage and so it picked up a water mold. This could also come from water splash if using an overhead watering system. Check a few plants to see if there is any life remaining in the small crown. If there is, then your assumption about premature dormancy was correct. I don't know what else to tell you.

Q: When is the best time to move or divide asparagus? (Forman, N.D.)

A: A lot depends on the weather and soil. The best time is early spring. If you can’t do it then, fall is perfectly acceptable. This is a very hardy perennial and shouldn’t have problems either way.

Q: I know someone that is having trouble with her asparagus. The first harvest this year was fine. The rest have not been. When she comes to harvest them, the main stem is soft and the portion to harvest is wilted and soft to mushy. She starts new plants every year from seed and rotates spots. She is a very good gardener so that rules out some of the normal and obvious issues. (Steele, N.D.)

A: Asparagus can suffer from frost damage, which might be the case with her plants. It could possibly be bacterial soft rot, but I doubt it from what you have told me about her gardening expertise.

Q: When and how should I clean my asparagus bed? I started the bed quite a few years ago and have kept a spot going through the years. (Herrick, S.D.)

A: Wait until fall after a couple of hard frosts. After you have cut down the ferns, get in there and do your weeding. If you go this Web site,, you will find ample research-based information for all kinds of weed control in your asparagus.

Q: What varieties of asparagus would grow best in North Dakota and can you suggest a source? You have said a hungry deer will eat almost anything. Will they eat asparagus? Will hail in late summer harm the crowns? (E-mail reference)

A: I don't see why deer would ever pass up asparagus since we humans find it so tasty. Hail damage may occur, depending on the hail size and intensity. The crown is buried beyond direct contact, but if the fern is extensively shredded, it will not make enough food for next season's growth to be adequate. Viking, Mary Washington, and Jersey Giant are good varieties. Just about any seed catalog that you receive in the mail should have these varieties.

Q: My asparagus has already emerged but I was told that I could still use princep on it. After reading your information, I'm thinking that perhaps I shouldn’t. I have purchased the princep but have not applied it. Can I use it or is there something else that you would recommend? (E-mail reference)

A: Once the asparagus spears have emerged, no herbicide is recommended. Herbicide applications should be made in early spring. If your weed population is too high, it may be necessary to dig and reset the crowns in a more weed-free environment. Some herbicides I found in my references for use on asparagus are 2,4-D, Dicamba, Glyphosphate, Linuron, Paraquat, Sethoxydim, Simazine, Terbacil, and Trifluralin.

Q: I love asparagus so I bought one plant from a greenhouse. I planted it this spring and know it will be two or three years before it produces. I haven't done anything to it except weed control and water it. It is growing but I don't know what its suppose to look like or if it will produce sort of like rhubarb. What care do I need to do? (Jamestown, N.D.)

A: It should be in the "fern" stage right now. Just let it grow, and scatter some 5-10-5 or 10-10-10 fertilizer over the area this fall. You can begin harvesting some of the spears next spring.

Q: I know that rust is talked about in asparagus, but is there a form of root rot that affects it. I understand that a patch in this area appeared completely rotted. Could too much rain and standing water do that too? (Cando, N.D.)

A: You bet! That's why when setting the crowns initially care is taken to assure good drainage conditions. There will never be a better opportunity.

Q: I have a problem with grasses in my asparagus beds and my raspberry patches. I have heard that a herbicide by the name of Poast is effective in controlling this problem. Can you tell me if I can use it? (Richville, M.N.)

A: Poast is a very effective grassy weed control in raspberries. Here the basics: 1) Do not apply closer than 45 days before harvest. 2) It is effective only against actively growing grasses, with annual grasses being between 3 and 8 inches tall and quackgrass 6 to 8 inches tall at the time of application. 3) Use either a crop oil or a nonionic surfactant according to label directions.

Q. Asparagus is salt tolerant and I would like to salt its soil to keep weeds down.
1.Will salt help the plants, or have a neutral effect?
2.How much salt should I use?
3.Should the salt be left on the surface or tilled into the soil?
4.Should the salt be applied before or after planting?
5.If after, how often?
6.What other aspects of using salt around asparagus should I keep in mind?
Thank you. (Howard, S.D.)

A.With my master's degree in soils, I just cannot bring myself to recommend salting the soil deliberately to control weeds.

There are herbicides that you can use to control both the grass and broadleaf weeds. Sinbar can control emerged annual broadleaved weeds and Fusilade or Poast will control emerged grasses.

For pre-emergent treatment, use Princep or Devrinol. For really obnoxious perennials, including quackgrass, use Roundup, applying at least one week before the first spear appears.

Salt use will destroy the structure of the soil and would not be a complete herbicide anyway.

Q: We know about harvesting asparagus only at the beginning of the season and then letting it grow to make food for the next year's crop, but I'm wondering about whether we should harvest all the spears, thick and thin, when we're harvesting, or should we just be harvesting the thicker ones? We didn't get around to seeding some Kentucky bluegrass in a sizeable area until late spring. What are the drawbacks for seeding this late? We have several apple trees that have set too much fruit. Other than hand picking some of it off, which isn't practical on our bigger trees, how can we thin out some of the fruit? (Actually, in this area, Mother Nature does a pretty good job of thinning, but sometimes even she needs some help!) ( Aberdeen, S.D.)

A: Harvest all the asparagus spears. From an edible standpoint, the thin ones will be just as tasty and nutritious; from a marketing one, only the thicker ones are used. No drawbacks to the grass seeding. In fact, everything is in your favor. Warmer soil equals faster germination, you are past the spring "flush" growth of weeds and hopefully the washout rains of earlier plantings. You may have to be a little more conscientious about water for the young seedlings should the hot weather of summer bear down too much. A couple of mistings during the mid-morning and afternoon of those days would be good to keep them from becoming heat stressed. There is nothing currently on the market that dependably helps thin apple fruit for the homeowner. You are right, though, June apple drop helps to naturally thin the crop for you. I would suggest trying to brace or support those branches that seem to bearing the heaviest load to prevent breaking during a windstorm.

Q: I have a question on asparagus. I have a lot of weeds in my patch. If I put leaves over the patch and leave it there, can they come up? If not, what can I do? (e-mail)

A: Yes, the asparagus will come up through the leaves, but depending on the weeds you have growing amongst them, so may some of the weeds. I suggest following through with your plan to use the leaves, and then carefully "wick-wipe" any weeds that come through with Roundup to kill them. Sooner or later, though, you will have to face the fact that the asparagus bed will need to be re-set in a weed-free area, as the weeds compete for water, nutrients and space.

Q: Previously I wrote to you and you diagnosed my strawberries as having angular leaf spot. We tilled some of our plants under before we realized that it is carried over in the soil. What can I plant in this spot now that won't contract this disease? I've been thinking about asparagus, but I'm not sure. (New Salem, N.D.)

A: Asparagus and/or rhubarb sounds like a winner to me! These two are fairly tough and dependable. 

Q: How do you get asparagus plants to grow? There are red berries on my plants now. Is that how they reseed?

I also have an umbrella plant that is about 11 years old. We cut the tops off of two of the stalks and now one sprouted out leaves about 6 inches from the bottom. If I cut them off and replant, will they grow? (Milnor, N.D.)

A: Yes, those asparagus fruits contain seed. Harvest after a good frost, and sow in a well prepared area next spring. The resulting plants will eventually be productive.

If you are referring the Schefflera, you will likely have cuttings that are too large to root. If you take the top 9 to 12 inches off and place them in a sand/peat mix (50/50), they will have a better chance of rooting. You will likely also get sprouts coming from the base of those canes as well.

Q: When the asparagus is no longer being cut, can the patch be sprayed to kill the grass/weeds? If so, with what? In previous articles you have suggest chemicals such as Dacthal, Devrinol, Poast and Prism for use in strawberry patches. Can any of these be used after the strawberries are harvested? I found the product Preen, but it says to use only on Beach strawberries. What are they? (Tripp, S.D.)

A: Yes, you can use Poast on the asparagus. Beach strawberries are, I think, the nonedible ornamental form.

Q: Is there anything I can spray on my asparagus patch to kill weeds but not the asparagus? (Doland, S.D.)

A: For the first year a hand weeding is the only way, but in subsequent years, the use of herbicides is recommended. Some herbicides to use are Treflan, Poast, Sencor 4 and Trific 60D7. Make sure to follow all label directions.

Q: I am enclosing a card with two bugs taped to it. These bugs are on my asparagus, but I have small black things sticking out of the spears. (Woonsocket, S.D.)

A: Thanks for somehow getting identifiable samples to me. I'm surprised they were not squashed in the mail!

You have two different species of beetles feeding on your asparagus. Since you are now past harvesting, spray with Sevin insecticide. Then in the fall, clean up any crop residue to prevent overwintering protection.

Q: What kind of fertilizer should I use on my asparagus? (Kimball, S.D.)

A: Asparagus benefit greatly from liberal fertilization practices—either composted manure, or a regular garden fertilizer like 10-10-10 at about 2 cups per 10 foot of row, but at this point in the spring you may be better off waiting until after harvest to fertilize.

Q: I am having a problem controlling grass in my asparagus bed and also my raspberry patch. I have been told that asparagus will tolerate salt, but grass will not. Can I sprinkle salt on my asparagus bed without killing the plants? I have also been told that Poast will kill grass but is not harmful to my plants. Can I safely use this on my asparagus and raspberries? (Richville, Minn.)

A: I try to discourage the use of salt. Yes, Poast will work with both species of plants. Be sure to follow label directions.

Q: I would like some information on propagation and transplanting of Juneberries. Also I need some information on how to remove grass from my asparagus bed. Thank you in advance for any information you will send me. (Sheyenne, N.D.)

A: Refer to "Juneberry" (H938), a publication of the NDSU Extension Service.

Judging from your description of the weeds invading your asparagus patch, I think you would be better off digging the entire thing up and resetting it somewhere where the weeds are not as troublesome. While salt water can take out most of the weeds, it is not good for the soil. Even though asparagus can tolerate some salt, its presence will inhibit the normal growth of the plants.

Refer to "Asparagus and Rhubarb" (H61), a publication of the NDSU Extension Service, which should provide you some guidelines. Hope all of this helps.

Q: What is best to put on strawberry plants for winter, and how should I care for my asparagus? Is it OK to put orange and grapefruit peeling in the garden? Is it OK to till poplar leaves into the garden? (Gackle, N.D.)

A: Either put up a snow fence around your strawberries, or cover them with clean straw, right after freeze-up but before serious snow falls.

Allow the tops of your asparagus to remain. They will influence snow collection, which rovide critical moisture next spring.

I'm assuming that you are composting your peelings first— if so, then OK. If not, then no.

You can till the poplar leaves into your garden soil. Just don't overdo it, or you will tie up nitrogen next year.

Q: Can you tell me the best way to control weeds in my asparagus? (Fargo, N.D.)

A: The asparagus plants should now be dormant. I'd suggest cutting the ferns back to ground level and carefully spraying the weeds with Roundup.

If there is no quackgrass present, I would suggest a shallow tilling next spring before the spears emerge, then apply a herbicide like Princep 80W or Sencor 50W. Follow the label directions.

Q: I have an asparagus fern that I transplant in early spring, and I never cut it back. Should I? Is it better to transplant them in the fall? Also, will they tolerate a light frost? (Litchville, N.D.)

A: Asparagus ferns are beautiful and somewhat tough. They will survive light frosts. I'd suggest throwing a sheet or newspaper over them when a light frost is called for. You are doing the correct thing by transplanting in early spring, and if you've been successful by not cutting them back, why start?

Q: I have an old patch of asparagus that is overridden with grass. Is there a chemical that can help me to restore the patch the right way? (Litchville, N.D.)

A: Yes, you can use Poast to rid the asparagus patch of grass. However, it would probably be beneficial to dig and reset some of the crowns in another location, since so much time has passed. Refer to the enclosed publication on growing asparagus ("Asparagus and Rhubarb"—H61).

Q: I'm a neighbor from South Dakota and have read your article many times in the Farm Forum. I'm very interested in weed control for winter onions and asparagus patches. I would like to know what  o use on these two vegies and also where you can get "Poast." I've asked about it at different places and they don't seem to know anything about it.

A: Hi neighbor! Glad to help out! Here is an abbreviated list of herbicides to use on your two crops: Devrinol, Karmex, Poast, Roundup, Sinbar, Treflan, and 2,4-D can be used on asparagus. On onions, Buctril, Dacthal, Fusilade, Goal and Roundup are cleared. Always be sure to follow label instructions in using these herbicides. As far as being able to find Poast goes, I checked with Tessman Seed here in Fargo and they do carry it. They are wholesale distributors for the Upper Great Plains region and could likely give a source for purchasing. Contact them at (701) 232-7238 and ask for Doug or Liz.

Q.Asparagus is salt tolerant and I would like to salt its soil to keep weeds down.

1.Will salt help the plants, or have a neutral effect?

2.How much salt should I use?

3.Should the salt be left on the surface or tilled into the soil?

4.Should the salt be applied before or after planting?

5.If after, how often?

6.What other aspects of using salt around asparagus should I keep in mind?

Thank you. (Howard, S.D.)

A.With my master's degree in soils, I just cannot bring myself to recommend salting the soil deliberately to control weeds.

There are herbicides that you can use to control both the grass and broadleaf weeds. Sinbar can control emerged annual broadleaved weeds and Fusilade or Poast will control emerged grasses.

For pre-emergent treatment, use Princep or Devrinol. For really obnoxious perennials, including quackgrass, use Roundup, applying at least one week before the first spear appears.

Salt use will destroy the structure of the soil and would not be a complete herbicide anyway.

Q: What kind of fertilizer is best for my cucumbers and pumpkins, as far as high yield and early yield goes? I can order 25 pounds of 20-20-20 all-purpose fertilizer from one place for $24.41. Another option is 5 pounds of Miracle Grow (15-30-15) for $14.95. What kind of yield per season could I expect from 100 asparagus plants once they're established? I know it depends on about a million things, but could you just give me a ballpark figure? I've read you shouldn't start cucumbers or pumpkins to transplant more than two or three weeks before you set them out. Do you agree? Would you set them out about May 20 (I live near Jamestown) or is that still iffy since they are so tender? I will have black plastic down and cloches above them. (Jamestown, N.D., e-mail)

A: I prefer Miracle-Gro. It has a good spectrum of major and minor elements that others lack and doesn't cause excessive vegetative growth. Asparagus should yield between 40 to 50 pounds per 100 plants. The longer the cucumbers and pumpkins sit around waiting to be planted out, the more difficult it becomes to get them established. May 20 is still iffy, but gardening any time of the year in North Dakota is iffy! With the plastic down and clotches above them they should do OK.

Q: What product should I use to control grass in my asparagus this summer? (Pelican Rapids, Minn., e-mail)

A: There are several that can be applied. Just follow label directions. Treflan--preplant only; not good on emerged weeds. Poast 1.5E--very effective on quackgrass at high dose. Fusilade DX 2E--can use only on non-bearing crop. Roundup Ultra--apply either seven days before first spears emerge or after the last spears have been harvested.

Q: My asparagus bed (at least 40 years old) is root bound with quack grass, dandelions etc. Are the asparagus roots worth trying to transplant, and is this the time of year for such a project? Or is there a spray that could kill everything but the asparagus? (Jud, N.D.)

A: A 40-year-old asparagus bed has served its duty to humanity. Kill everything off this year and plant something else. If you still want to grow your own asparagus (I don't blame you for wanting to!) get some Jersey Giant crowns next spring and begin anew in a quack-free setting!

Q: I planted some three-year asparagus plants, and they came up very well. What do I do now? Am I supposed to cut them down to the ground or let them go to seed this first year? I should be able to harvest them next year, right? My asparagus is all ferny now. How many harvests can I expect in one year? Do I have to cover them over the winter? (Jamestown, N.D., e-mail)

A: Asparagus can be allowed to go vegetative the first year after planting to give the crown a chance to get well established. Next spring, remove the old fern growth from the previous year, and keep an eye open for the new spears to begin emerging. Harvest and enjoy! The fern growth is needed to allow the plant to replenish the nutrients for next year's spear production. The asparagus can be harvested for a period of about two to three weeks once the spears start to show. Some people push it longer, but I don't recommend going beyond that. Besides, even if you love fresh asparagus, 3 weeks of it is enough for most people! Do nothing over the winter. The ferns will be good snow trappers, and give you a rough gauge as to the depth of the snow.

Q: Can I use Prowl on my asparagus bed next spring as a pre-emergent herbicide? (Pelican Rapids, M.N.)

A: I cannot find asparagus listed on the label. If it isn’t there, its use would be considered illegal. Treflan is labeled and controls some of the same weeds as a pre-emergent herbicide.

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