Fertilizing Blackberries

Preparing the Soil

• Prior to planting blackberries, the amount of organic matter you add to the soil is more important that the actual content. The more you can enhance your soil with some sort of hummus, the better it can retain water and promote a good root system.

  Try to do this at least several weeks before you will actually be planting. Whether you use rotted manure, peat moss, homemade compost, or even extra topsoil, bringing some extra "fluff" to the future home of your blackberry patch will give the plants the best possible start. If possible, use material that will keep the area a bit on the acid side, with a pH somewhere around 6.0.

Feeding after planting

• After you've established your blackberry canes, and in following years, aim for at least one fertilizer application in early spring. Some growers suggest two feedings--once in early spring and once when the canes begin to blossom, about four to six weeks later. Use your own judgment, perhaps waiting to see whether the plants seem to be undernourished.

  Choosing the top-dressing method gives you the easiest, most direct way to apply fertilizer. To top-dress blackberry canes, simply drop a shovelful of your chosen fertilizer on top of the soil along your row.

Choosing your fertilizer

• If organic fertilizer just isn't your bag, so to speak, then apply 10-10-10 to your blackberry patch. This number refers to bagged, artificial fertilizer containing equal parts of "N-P-K"--nitrogen (N), phosphorus (P205) and potassium (K20).

  If you buy your plants through mail-order sources, chances are you'll be advised to feed the blackberry canes the grower's specially formulated "berry food." Take these recommendations with a grain of salt. Blackberries just aren't picky enough to warrant expensive blends, and you almost certainly won't be getting an organic formula.

  In fact, going organic remains not only the healthiest, but potentially the cheapest, route to feeding your blackberry plants. If you'd like to make Mother Nature's version of commercial fertilizer, the University of Georgia offers handy organic formulas for the equivalent of a 5-pound bag of artificial N-P-K in the 10-10-10 ration. One example blends 7.5 pounds soy meal (N), 4.5 pounds bone meal (P) and 10 pounds greensand (K).

  If you have alternate sources of organic matter, such as manure and kelp, check out a table like the University of Georgia's so you can customize your own all-natural N-P-K blend.

  Whether chemical or organic, a 5-pound bag of 10-10-10, or your equivalent organic bland, is about right for each 100 feet of row. Of course, if you're only growing about 50 feet of blackberries, use half of the bag in the spring and the rest during the blooming season; 25 feet would call for two applications of about 1.25 pounds each, and so on.

  Master Gardener Barbara Damrosch keeps it even simpler. She suggests top-dressing blackberry canes just once a year, in early spring, with a spadeful of compost or manure along every foot or so of the row.