Questions on: Blueberry

Ron Smith, Horticulturist, NDSU Extension Service


Q: I started growing four blueberry bushes. Two are growing like wildfire, but two died. I did nothing to the soil and only gave the bushes water. I didnít realize until recently that the bushes had special needs. My local gardening store told me to use Miracid, but Iím not sure if I should. I have four more bushes to plant, but I am scared to plant them. I have the bushes in pots and have them in the house, but they wonít last that way. Another gentleman digs a hole a foot deep and a couple of feet wide and then fills the hole with a mixture of soil and peat. I don't know what ratio of soil to peat he uses other than it appears to be mostly peat. He top-dresses new bushes with sulfur to counteract the surrounding native soilís tendency to raise the pH level. Every year after that, he places sulfur around the base of the bushes. Is this the best way to plant the bushes? (Pipestone, Minn.)

A: The practice the gentleman uses is the most surefire way to success.


Q: I enjoy reading your column and am interested in planting blueberries, sea orange (from Siberia?) and lingonberries. My plan was to dig up a good-sized garden area and amend the soil with peat moss and aluminum sulfate. My concern is the use of this aluminum compound. Is there any danger with using it and then consuming the resulting berries? Also, do you have any advice on the planting and care for these acid-loving plants? (West Fargo, N.D.)

A: Pure sphagnum peat moss and fertilizing with an acid-forming fertilizer, such as aluminum sulfate, will provide the crop you want. In naturally occurring acid soils found in the northeastern part of the U.S., aluminum is a common element. Getting the soil too acid will result in acid toxicity to the plant, not the consumer. Aluminum is not used in plant metabolism.


Q: I would like to plant blueberries on my property adjacent to Lake of the Woods. The plants would be about 300 feet from the lake. Do you have any suggestions on variety, elevated planting, peat moss, distance between plants, etc? (Warren, Minn.)

A: The University of Minnesota has done the work on blueberries for you. Go to www.extension.umn.edu/distribution/horticulture/DG3463.html and download the publication. I think you'll find everything you are looking for. Thanks for making contact.


Q: As you know, it has been very cold here in central Minnesota. Until recently, weíve had nighttime temperatures in the mid- to low 20s. I have a northblue blueberry bush that was loaded with buds. I have been covering it at night, but I forgot one night. Can I expect any fruit or did it spoil my chances? I have several plum trees in the same situation, no blossoms, but they are budding. (e-mail reference)

A: It all depends on how low the temperature went in your locality, the nutrient status of the plant, if the bush and trees had softened up too much during the brief warm spell and the moisture status of the plants and surrounding soil. In other words, I donít know. If there is no fruit on the blueberry or plums, the weather certainly can be blamed! I think you will see some fruit this year on both.


Q: I had someone call saying he recently planted some blueberry bushes. The booklet that came with them recommends using aluminum sulfate to lower the soil ph. He canít find aluminum sulfate around here, so he is wondering if doubling up on Miracid would do the trick. (Mandan, N.D.)

A: Doubling up on Miracid would kill the plant. He needs to scour the Internet to find a source or go through garden supply catalogs. If he still canít find it, he should use powdered sulfur and work it into the soil, which should be almost 100 percent sphagnum peat moss.


Q: I live in northeastern South Dakota and am considering starting blueberry bushes. I have a 40- foot garden and would like to know how far apart to plant them, and also the space required on the opposite sides based on the fact they would be planted in a row. I have a spacious garden and would appreciate your suggestion as to what variety or varieties one should plant. (E-mail reference, S.D.)

A: Here are the requirements for growing blueberry bushes in your part of the country: 1.First, get the soil tested, and indicate that the crop intended is to be blueberries. Since your soil is likely alkaline or at least neutral (pH 7), you will have to incorporate sphagnum peat moss and sulfur thoroughly into the planting site, prior to planting the shrubs. 2.Assuming you have a sandy soil or a loamy sand, and a pH reading of 7.0, you would need to apply 19 pounds of elemental sulfur per 1000 square feet, and 1.5 to 2.0 cubic feet of peat moss per plant. If you soil is loam or clayey loam, then 58 pounds of elemental sulfur per 1000 square feet will be needed. Incorporate no less than 2 cubic feet of sphagnum peat per plant. 3.Spacing is not super critical on the scale you are working with. Depending on the equipment you have available, you can use a spacing of either 4'x8' (in rows x between rows) or 3'x8'. 4.I suggest getting at least 1-year old transplants, and at least two different cultivars for superior production. While not necessary for production, this cross-pollination among the different cultivars will result in better production and larger berries. Bees are necessary for this to take place. If you have a friend that keeps hives, you might offer your patch of berries for that purpose. 5.The cultivars I would suggest come from work done at the University of Minnesota. Look for Northblue, Northsky, and Northcountry cultivars. 6.Fertilize with ammonium sulfate to help keep the pH low. Provide winter protection and irrigation; as the plants need frequent, light irrigation since the roots are thin and fibrous. Be able to provide at least 1 inch of water per week during the growing season. 7.Two important final points. Blueberries need good drainage and winter protection. If you have heavy clay soil, consider excavating it and replacing it with sand or sandy loam. Straw mulch going into winter is also a necessity.


Q: When does sunscald occur on shrubs such as blueberries, Saskatoons and currants? What can we do to protect the plants from this damage? Also, what can you tell me about what and when to spray to keep currants etc. from having worms in them? (Westhope, N.D., e-mail)

A: These shrubs are generally not prone to sunscald, which usually occurs on thin-barked trees such as apples or pears when they are young, and on the southwest side of the tree. Protection is generally achieved by painting with whitewash or wrapping the trunk with cloth. It occurs when the sun hits the dark colored bark and raises the temperature at that location to 50 F or 60 F or higher--and the air temperature is still below freezing. When the sun goes down, the cell tissue ruptures at that site and sunscald occurs.

As for your insect question, spray with Sevin when the shrubs are in flower. Keep in mind that Sevin is toxic to bees, so spray at a time when they are not active--either in the early morning or evening. Spray again right after blossom drop.


Q: I received a catalog from New Jersey that has blueberries. Can I grow them here in Brookings? I've heard that they take a special type of soil. Can the soil be modified? I also got some blueberry jam for Christmas and it was really good! That's why I am interested in blueberries. Or should I just buy the berries? (Brookings, S.D., e-mail)

A: It all depends on how much you like challenges. Yes, blueberries could possibly be grown in Brookings, but it would take major modification to make the soil acid enough. I would suggest getting some Canadian Sphagnum peat moss and literally making a raised bed with about 80 percent peat and 20 percent soil. While I enjoy challenges, I find it easier to simply purchase the berries when they are available at the store.


Q: Can you tell me what is wrong with my North Blue blueberry? The leaves are curled under and don't look very happy. (Sioux Falls, S.D.)

A: The blueberry problem could be related to the pH of the soil. The reading should be around 5.5.


Q: I heard that blueberries can be grown in my area and I am wondering what kind of blueberries would be best suited for my area. I would also like to know when is the best time to plant blueberries and what type of soil is needed. (Carrington, N.D.)

A: Blueberries in North Dakota? If so, they are growing in very highly modified soil.

Normally, blueberries need an acid soil, high in organic matter, with a pH range of 4.5 to 5.0all of which is literally unheard of in native North Dakota soils. They also are not winter hardy at temperatures below -20 F.

If you make a bed of 50% sphagnum Canadian peat and mulch the plants before winter closes in, then you might be successful. As far as the cultivar selection goes, I would suggest the Northsky out of the University of Minnesota (UMN) breeding program. It is the shortest of the three (Northblue and Northcountry being the other two) and would have the best chance of surviving the brutally cold winters of our region.


Q. How long does it take blueberries, Juneberries and grapes to bear fruit? (Devils Lake, N.D.)

A. Blueberries can only be grown with Herculean effort in North Dakota. I am sure there are a few devoted gardeners who have succeeded, but it is not worth the effort and expense. Generally, they begin producing after two to three years.

Juneberries are the most logical small fruit to grow from your selection. Mine started producing after three years, but the birds get them all as they ripen.

Grapes also require about three years before any production can come off to any degree. Beta, Canadice and King of the North are the most dependable cultivars to try. All are good for making jams, jellies and wine (or grape juice). Others can be grown, but generally require extra protection for survival and production.


Q: We just moved to a new house and it has raspberry and blueberry bushes. I have no experience working with either and was wondering how far back I should cut them before winter and when is the best time? (E-mail reference, Hillsboro, Ore.)

A: Both plant species should grow like weeds in your area! Raspberries have two cane types -- the primocane grows the first summer and normally remains vegetative or non-fruiting for that season. In the second summer, that same cane produces floricanes, or fruit bearing branches. Once the fruit ripens, the cane begins to senesce or die. New primocanes are produced each year, so fruit production is yearly. Once these fruit-bearing canes stop bearing, it is a good idea to remove them completely, and burn them. The longer they stay with the plant, the greater the opportunity for insect and disease problems to develop. Blueberries need only to have their weaker branches pruned. This is generally done in the early spring before the buds open. The important thing with blueberries is winter protection. Not knowing the winter extremes in your area, I suggest contacting your local extension horticulturist or other folks who have blueberries as well and see what their cultural practices are. Low pH (4.5), continuously moist soil, adequate fertility, and winter protection are the key factors in blueberry production.


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