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Published June 21, 2009, 12:00 AM

PRAIRIE GARDENER: Lovely lilacs

A garden staple in cold-winter regions, lilacs are best known for their flamboyant and typically fragrant flower clusters. And just when you thought we were done with the lilacs for another season, there is another on the scene — the Japanese tree lilac.

By: Darrel Koehler, Grand Forks Herald

A garden staple in cold-winter regions, lilacs are best known for their flamboyant and typically fragrant flower clusters. And just when you thought we were done with the lilacs for another season, there is another on the scene — the Japanese tree lilac.

Little known in comparison to the old-fashioned lilac and the French hybrids, the Japanese tree lilac is the last to bloom, usually in late June or early July. Winter-hardy, this lilac can be grown as a large shrub that grows up to 30 feet high or as a single-trunked tree. It has smooth bark, similar to cherry bark in glossiness. The leaves reach 5 inches in length. The white flower clusters it produces are up to 12-inches long, and are produced on new growth late in the lilac season. They are a sort of ivory-white and lacey in appearance, kind of like an old-fashioned hanky. Unfortunately, they don’t have the delightful aroma of other lilacs. Some compare their somewhat unpleasant odor to privet flowers.

The tree lilac is hardy through Zone 1, so you don’t have to worry about winter damage. However, the Prairie Gardener did have a problem with powdery mildew, a common lilac ailment, in his tree lilac. A cool, damp summer followed by more of the same in autumn brought on the fungal disease, which left some dead branches. They were removed, and the tree has since filled in those bare areas.

Varieties

There are literally thousands of lilac varieties from which to choose. This spring, they did especially well in this region as they prefer cool, moist conditions. Many lilacs originated in the Balkan region while others are native to Asia. Wedge’s Nursery in Albert Lea, Minn., once specialized in lilacs, offering a catalog of hundreds of named varieties to customers.

Lilacs prefer full sunlight to perform best. They like a well-drained, neutral to slightly alkaline soil. If the soil is too acid, lime should be dug in before planting lilacs. Most lilacs bloom on new wood, so prune just after flowering ends. Remove spent flower clusters, cutting back to a pair of leaves; growth buds at this point will make flowering stems for next year. Renovate old, overgrown plants by cutting a few stems to the ground each year.

If you have a severe problem with powdery mildew, apply a fungicide to your lilac as you spray fungicide on other plants in your garden. Applications should be made about every 10 days, especially during humid weather.

Lilacs were among the first flowers brought to the New World, and were a common sight by 1652. They followed settlers westward, ending up on the Northern plains in the late 1800s. You can still find them around abandoned farmsteads, offering up that pleasant lilac aroma each spring. A bouquet of old-fashioned lilacs can freshen up a room. Little wonder so many gardeners look forward to lilacs each spring. The Japanese lilac is just one way to extend the season, but, unfortunately, without the delightful smell of more common varieties.

Iris time

Today is Father’s Day and during the weekend we will also celebrate the summer solstice, the longest day of the year, as well. Among Scandinavian-Americans Wednesday will be observed as Mid-summer’s Day while Finnish-Americans will observe it as St. John’s Day in honor of the feast day of St. John the Baptist. Typically, the peonies are in full bloom by this date, but they will be a bit later this spring.

Irises , which are running 10 to 14 days behind schedule, are among the easiest perennials to grow, coming in many colors. They have to be divided and replanted about every three years. A great source for irises is Beau Jardin Iris Gardens located south of Moorhead, Minn., on U.S. Highway 75 in Wolverton, Minn. They offer the tall bearded iris with more than 500 varieties planted. A spokeswoman said they garden is closed to the public this season as they regroup. Hopefully, they will be back next year.

Brown evergreens

Many of our evergreens emerged from our severe winter with rust-colored foliage. In the worst cases, they are dead. These often were the parts that stuck up from the snow, which turned brown. The situation is even more severe if the evergreen was in an exposed site where wind and sun were strong, and the plants may have gone into winter without adequate moisture such as along a foundation.

There’s nothing new you can do now other than wait to see if new growth develops. The brown, dead needles will drop, eventually. If the shrubs still look sparse after new growth appears, you will have to decide to either put up it or replace them. Yews, arborvitae and junipers continue to put out growth throughout the growing season, so they should improve as time passes.

Lawn moss

While severe winter brought much damage to perennials and trees, our lawns haven’t fared much better due to cool, moist conditions. Some gardeners are reporting finding moss in their lawns. Moss does not develop in healthy lawns. Lack of fertilization, soil compaction, poor drainage, shade and poor soil aeration are the common causes. To correct the problem, fertilize and aerate the soil. Also, prune trees and shrubs to allow more light to r each the soil, and to improve air circulation.

Rose damage

While tender rose damage wasn’t uncommon here this spring, it can occur elsewhere such as in the Lauritzen Gardens in Omaha. While we can blame the severe cold for damaging our roses, Nebraskans have a different problem — freezing and thawing. A horticulturist at the garden said they expect to lose a quarter of their tender roses to this problem each winter. So, just living in a warmer climate doesn’t ensure you won’t have rose woes.

Rabbit woes

Not only have gardeners been facing a barrage of strange weather conditions this spring, including too much and then too little moisture, temperatures had been running below normal until recently as well. Added to this strange mix have been hungry rabbits. Cottontails have a special hankering for tender bean shoots as they emerge. A good way to keep the bunnies at bay is the product, Liquid Fence, which is available at most garden centers and similar outlets. Several applications are required.

Circle dates

The 25th annual Grand Forks Horticulture Society garden tour will be July 18-19. Several of the top gardens in this area will on view. For more information, go to gfhort@usa.net.

Happy Father’s Day!

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.

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