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Published September 27, 2009, 12:00 AM

DARREL KOEHLER: Raspberry patches can be renovated any time from late summer until late March

The single biggest stress facing trees over much of the state has been the exceptionally dry weather early in the growing season in recent years. Other stresses include insect damage and, construction damage caused by compacted soil.

By: Darrel Koehler, Grand Forks Herald

While the full-blown fall color season is still down the road, you would never know it in some areas of Minnesota. Fall colors normally peak around here in early October, but some trees are already making the switch.

The situation is even worse in areas of Minnesota hard-hit by summer drought, such as St. Cloud, Stillwater and other areas of the eastern part of the state. While we are better off, we have moisture shortage problems in some areas as well as too much up along the Canadian border in Minnesota. The problem of stressed trees is particularly noticeable at the Minnesota Landscape Arboretum near Chaska. Some trees were already shedding their leaves over the Labor Day weekend.

The single biggest stress facing trees over much of the state has been the exceptionally dry weather early in the growing season in recent years. Other stresses include insect damage and, construction damage caused by compacted soil.

The problem is particularly severe if you have newly planted trees. Trees do require good moisture supplies for at least the first five years and even longer if we have a severe drought. The prematurely falling leaves don’t have the vibrant of normal leaves. But there should be enough fall color for everyone to enjoy.

Berry queries

There have been several queries this summer about how to prune raspberries. Normally, this task is done after the berries bear fruit. But there are some exceptions. Unless pruned and trimmed, a berry patch will resemble a thicket in short order. You also will end up with poorer quality fruit.

According to the University of Minnesota Extension Service, summer-bearing raspberry patches can be renovated any time from late summer after harvest until late March of the following year. Late summer is probably best because you will end up with more vigorous canes and larger fruit. If hardiness is a concern and if canes may be lost to winter damage, renovate the raspberries in March, instead.

To renovate, remove all canes that have already produced fruit (they should have brownish bark as opposed to green for new canes) and then broken or damaged canes. It’s best to leave four to six canes per foot of row or seven canes per hill if you use the hill system. Canes selected should be sturdy, healthy and have room to grow. Don’t cut back canes until the next spring when winter damage can be determined.

Berry rules

Raspberry rows should be no wider than 12 inches to allow for the best light penetration and air circulation. Don’t fertilize in summer and wait until early spring to apply nitrogen. Summer is a good time to apply 12 inches of mulch, such as straw, sawdust or compost.

If you have fall-bearing raspberries, such as “Heritage,” “Red Wing”or “Autumn Bliss,” you can renovate them as you would summer-bearing raspberries. However, the canes that produced the fall crop should not be removed as they will produce the berries the next summer. Prune them back in spring to the last node that produced fruit.

Another option is to cut all canes of fall bearers back to about 2 inches above the soil surface in late fall when plants are dormant or early spring when dormant. You will harvest only one crop in the fall, but the yield will be greater and the quality of the fruit better.

Trees named

While emerald ash borers are poised to kill many of the ash trees in the region, foresters are looking at possible replacements. In wake of the Dutch elm disease problem, we replaced the elms with green ash. We don’t want to make the same mistake of planting a single species twice in a row. We have found planting a variety of tree species is the route to go if another calamity should strike. Or, we could end up doing the same thing down the road.

Possible replacements include new elms that show resistant to Dutch elm disease. This would include both American elm and hybrid elms. “Valley Forge” would be a good American elm, “Accolade” for the hybrid category. There are several maples that work well, particularly those with silver maple background. “Autumn Blaze” would be in that category. Hackberries aren’t particularly attractive when young, but will form a nice canopy when older. They tolerate tough sites. Rounding out the list would be little-leafed lindens or basswoods. They have small flowers in late spring or summer.

Garden briefs

• A new temporary exhibit: “How Does Your Garden Grow? Gardening in North Dakota” opens Nov. 20 at the North Dakota Heritage Center in Bismarck. It will trace more than 900 years of growing horticultural crops in the state. It begins with the Indians who raised corn, squash, sunflowers and beans along the Missouri River to traders and settlers who brought vegetable seeds when they moved to the region. These horticultural products were often the key to surviving a Dakota winter. Horticultural artwork from the former Oscar H. Will & Co., nursery in Bismarck will be included as well as other artwork.

• The East Grand Forks Campbell Library is seeking donations of perennials, bulbs and other plant materials for its gardens. You can bring your surplus to the library or call (218) 773-9121. The gardens will be expanded this fall.

• The Memorial Garden was dedicated early this summer at the Circle of Friends Humane Society, 4375 N. Washington St.. The garden was constructed over several years for area pet owners to honor the animals that were such a part of their lives. The garden is a reminder of what a large impact pets have on us as we mourn their passing.

• The 13th District Horticultural Society of Minnesota in the northwestern corner of the state observed its 50th anniversary last weekend. The 13th District dates from Sept. 19, 1959, when the Ninth District was divided into two districts, 11 and 13. The celebration was at Messiah Lutheran Church in Roseau.

• Gardeners from throughout the region are excited about Minnesota’s latest gift to the apple world — the SweeTango. An offspring of the famed Honeycrisp and the Zestar, it is expected to top Honeycrisp in popularity in future years. While it may not be available locally for a year or so, and we don’t known how well it will take our winter, we will wait anxiously for its availability. It will be hard to beat a Honeycrisp, but this new apple may just do so. Some select supermarkets in the Twin Cities will be offering SweeTango apples this fall, if you want an early taste.

Koehler is the Herald’s garden columnist. His column is published every Sunday in this section during the growing season. Send garden questions to him in care of the Grand Forks Herald, Box 6008, Grand Forks ND 58206-6008. Tune in the weekly garden show airing at 4:10 p.m. Thursdays on KNOX Radio 1310 (A.M.) The show ends Oct. 8, resuming in the spring of 2010.