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NORTHERN MAGNOLIAS, DECLINING OAKS, AND CORN GLUTEN FOR LAWNS
It's been a great growth year for trees and shrubs. I planted a lot of trees and shrubs when I built my house in 1993 and the combination of root systems that are just now venturing beyond their planting hole and this year's plentiful moisture have led to some remarkable growth.
People often ask why their trees and shrubs don't seem to be growing. Often, several follow-up questions reveal that the plants were just put in the ground this spring, or within the past two years. What many people don't realize is that the roots of newly planted trees and shrubs can require years to get established. Also, the larger the plant, the longer it takes to get that plant established. I've seen research demonstrating how small seedlings can equal the size of much larger trees
One shrub that has really flourished in my yard this year is a Royal Star magnolia, one of only a handful of magnolias that can survive our cold winters. It bloomed sparingly last spring. If its lush growth is an early indicator, however, it should be loaded with blossoms next spring.
Royal Star is a shrub form of magnolia that can grow to a spread of 8-10 feet. Two tree forms of magnolia that do well in Minnesota are "Dr. Charles Merrill" and "Leonard Messel." Both of these can grow to a height of 20 feet with a spread of 10-12 feet.
According to Mary Maguire Lerman of the Minneapolis Park Board, Dr. Charles Merrill has a fragrance that is a "perfume knockout you will enjoy!" Its flowers are white and waxy. The flowers of Leonard Messel have a white upper flower petal color, while the under side is pink. On breezy days, these petals flutter, causing a "pleasing rose-pink effect," according to Lerman.
Magnolias prefer a moist, well-drained, organic-rich soil in sun or part shade. Avoid planting them directly against foundations or in hot-dry south-facing areas.
Declining mature oaks
One of the saddest sights I've seen this summer is a stately old bur oak tree standing in a front yard of a new home in a southern Twin Cities suburb. The tree is only a skeleton - its life was taken by the stresses of home construction.
When an oak forest is converted to a housing development, the large oak trees still standing are intended to provide beauty, shade and value. These remaining trees, unfortunately, are subsequently exposed to higher summer temperatures and drying winds. Then we make them even drier and hotter by disrupting their root systems.
Excavations for sewer, water, electricity, natural gas, basements and driveways all take their toll. Changing soil levels around roots further contribute to root damage, decay and smothered roots. Stumps of removed trees allow root-rotting fungi to build up and penetrate nearby living root systems. Over a period of years, the once-healthy oaks fall prey to root system destruction and pests.
Damaged and stressed oaks open the door to two-lined chestnut borers, which cause branch dieback and tree mortality. Two-lined chestnut borers derive their food from the outer sapwood and thin film of phloem in the inner bark tissue. You can confirm their presence by finding elongated white larvae and winding galleries under the bark of dead and dying oaks. If you discover evidence of two-lined chestnut borers, remember that the borers are a symptom of the underlying root disruption and exposure problems of oaks following construction damage. They were not the primary cause of an oak tree's decline.
Corn gluten meal
If you're among the growing number of people who rely on corn gluten meal products to prevent weed seeds from sprouting in your lawn, August is the time for a second application. Last spring's application will have lost its effectiveness by now. A new application will prevent weed seeds from sprouting now and, more importantly, will prevent weeds known as winter annuals from sprouting this fall, then returning next spring.
Apply corn gluten meal at the same rate recommended for spring - 20 pounds per 1,000 square feet. Water it into the lawn to activate. Corn gluten meal also provides slow-release nitrogen that should help grass thicken this fall and come back better in spring.
Remember, corn gluten meal is effective against a wide variety of seeds. It cannot discriminate between weed seeds and seeds from desirable turf grasses, so if you're planning to over-seed your lawn this fall, do not spread corn gluten meal in that area. Wait until spring when the new grass plants are growing vigorously before you apply it again (late April or early May).
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PUTTING DOWN ROOTS:
A Delightful Blend of
Gardening Wisdom, Wit
and Whimsy
$10 + $2 for shipping
by Cliff Johnson |
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