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Ask a Master Gardener: Wisteria still possible in Minnesota

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news Brainerd, 56401
Brainerd MN 506 James St. / PO Box 974 56401

Dear Master Gardener: My brother and I miss the beautiful and fragrant wisteria that grew along our porch roof in Alabama when we were growing up. He claims that it can be grown here in Minnesota but I doubt it because I’ve never seen it here. Who is right?

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Answer: Your brother wins this one. Most species of wisteria grow south of Minnesota but one, Kentucky wisteria or Wisteria macrostachys, is hardy here and is carried by local nurseries. It is a spectacularly beautiful, early-summer, twining, woody, deciduous climber with fragrant, pendulous white, pink or blue-violet flowers that frequently rebloom later In the summer. It also has attractive, long, dark green leaves with oval leaflets and an interesting, gnarled trunk. It likes full sun and moist, rich soil. Several cultivars thrive in Minnesota: “Aunt Dee,” “Blue Moon,” and a new one called “Summer Cascade.” Northland Arboretum in Brainerd has had a lovely “Aunt Dee” for a number of years. There may be some reasons why wisteria is not more popular here. First, it needs a sturdy wall, stake, trellis or pergola. Second, it takes several years to settle in before blooming. Third, it can be very aggressive and definitely requires pruning—sometimes 2-3 times a year, both to contain it and to force heavier bloom. It is not a plant for the casual gardener. But it is so beautiful that you may have strangers stopping by to ask you what “that gorgeous plant” is.

Dear Master Gardener: I would like to plant some raspberries and blackberries this summer and was wondering which ones are best for the Brainerd lakes area and what are some tips for successfully growing them?

Answer: Blackberries are typically not winter-hardy up here, but raspberries are. The following information on raspberries is from Professor Emily Hoover, of the horticulture department at the University of Minnesota.

The three main types of raspberries that can be grown in the home garden are red, black and purple. Raspberries have perennial roots and crowns, but the canes only live for two summers. The first year, the new cane (primocane) grows vegetatively. The cane over-winters and during the second growing season the second-year cane (floricane) produces fruit and then dies. Primocanes are produced each year, so fruit production continues year after year. Red and yellow raspberries produce numerous new canes from the base of the floricanes and from buds produced on the roots. Black and purple raspberries are not reliably hardy in our fruit zone.

Ever-bearing raspberries, also known as fall-bearing, are able to initiate flowers during the first year. These cultivars produce fruit at the tips of the primocanes. During the second year, they can produce a summer crop on the same canes. One problem with this type of raspberry is that in parts of Minnesota where the growing season is short, many fruits may be lost to early freezes.

Raspberries should be grown in a part of the garden that has good air circulation, good water drainage and full sunlight. Protect plants from windy sites because wind can cause excessive drying and cane injury.

Early spring is the best time to plant raspberries. Purchase disease-free plants from a reputable nursery. Viruses can be quickly transmitted into a planting through infected plants. The hedgerow is the favored planting system for red raspberries. Set red or yellow raspberries every two-three feet in rows at least 6 feet apart. Raspberry plants need to be fertilized. When primocanes emerge in new plantings, scatter ¼ cup ammonium nitrate (33-0-0) around each new plant. Once the planting is established, fertilize yearly by May 1st by evenly distributing fertilizer such as ammonium nitrate (1/5 cup) or 10-10-10 (1/2 cup) per plant, spreading it over the entire area. Composted manure is also a good source of nutrients and can be incorporated into the soil prior to planting and as a top dressing on established plants. Like many plants, raspberries benefit from mulch. Plentiful water is a necessity from spring until after harvest. Because the root system is in the top two feet of soil, watering regularly is better than an occasional deep soaking.

Raspberries benefit from some type of support system because canes are susceptible to wind whipping. This can be as simple as posts with twine tied between them, or more elaborate with permanent posts and wire. With the hedgerow system, the simplest trellis system uses single or double wires or twine. Place posts about every 10-12 feet; then place the canes between the wires and tie them loosely to the wire. The wires can be tied every 2 feet to prevent spreading. The rows should be kept narrow.

After the last harvest, cut all canes that have produced fruit to ground level and remove them. This will eliminate a disease source and give primocanes more room to grow. Thin the primocanes down to four or five sturdy canes per foot in each row. Since winter injury is common in this area, you can delay thinning primocanes until the following spring; however primocane growth will be less because of the competition among canes. It is desirable to cut the canes to about 12 inches above the wire before growth starts in the spring.

The list of cultivars below is based on research done through the Minnesota Agricultural Experiment Station. Hardiness ratings are based on the survival of plants in Minnesota hardiness zones. Fruit hardiness zones differ from USDA cold hardiness zones. Minnesota is divided into four fruit zones. Crow Wing County and the northern half of the state is Fruit Zone 4. The following cultivars are rated for Minnesota’s Fruit Zone four.

Cultivar, Type, Harvest season, Productivity, Fruit size, Firmness, Flavor

Latham, Red, Mid, Good, Large, Fair, Good

Boyne, Red, Early, Very good, Medium, Fair, Good

Nordic, Red, Early, Very good, Medium, Good, Very good

Festival, Red, Mid, Very good, Medium, Good, Good

Liberty, Red, Mid, Good, Medium, Poor, Good

Killarney, Red, Early, Good, Medium, Fair, Good

Fall Red, Fall, red, Early, Good, Medium, Poor, Good

Redwing, Fall, red, Early, Very good, Medium, Fair, Good

Summitt, Fall, red, Early, Good, Medium, Good, Good

Fallgold, Fall, yellow, Early, Fair, Medium, Poor, Superb

Autumn Bliss, Fall, red, Early, Good, Medium, Good, Superb

May garden tips:

• Work compost into garden beds as soon as soil is frost-free and friable. It will then be ready for planting at the end of the month.

• Install peony hoops before foliage is too tall to confine without injury.

• Clear debris beneath shrubs and trees.

• It is too early to spread pre-emergent crabgrass preventer. Wait until early June here in Crow Wing County. It’s also too early to plant tomatoes, peppers and melons before Memorial Day.

• Dig up dandelions now while their yellow blossoms make them easy to spot and to prevent their going to seed.

• If you are hungry for garden color, plant pansies, violets and johnny jump-ups now. They withstand cold snaps well.

• Sow snow peas, leaf lettuce, spinach and radishes directly into the garden as soon as the ground can be worked. Transplant onions, cabbage, cauliflower and broccoli while soils are still cool.

• Floating row covers can help protect emerging seedlings and still-tender transplants from squirrels, chipmunks, birds, rabbits and other small critters. You will need to secure row cover corners to discourage wily wildlife from sneaking under them.

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