Moxie Gardener

Ginkgo flowers fading at midsummer.

Ginkgo trees are living fossils that are not related to any living plant. Fossil records of related species end after the Pliocene era everywhere except a small area of central China.

The ginkgo tree lives for hundreds, sometimes thousands of years. There are specimens growing near monasteries in China that are believed to be 1,500 years old. Other specimens in China are known to be over 3,000 years old.

Four ginkgo biloba trees survived the nuclear bomb at Hiroshima and are alive in that city today.

They are one of the toughest, most resilient trees alive today and are widely planted in urban areas throughout North America. Few pests or diseases bother them and they can grow to over a hundred feet tall.

Their only downside is a foetid smell associated with their seed pods, which can smell like rancid butter or even feces.

The ginkgo tree is dioecious, which means it produces both male and female plants. Because the females produce the smelly seed pods, cuttings from male trees are grafted to seedlings and are planted more often than females. They still flower, but do not produce seeds.

The ginkgo tree turns bright yellow in autumn. They have an unusual quality in that their leaves turn yellow and fall off within a short 10 to 15 day period.

Ginkgo trees grow in full sun to part shade and will grow well in virtually any type of soil, as long as it is adequately drained. Their columnar shape and upright growth habit make them a natural as shade trees planted along city streets in USDA Zones 3 to 8.

They bloom in late June here in Zone 4 and their blooms last only a few days. The picture above was taken at midsummer, just when the flowers were starting to fade.

An Emerald Ash Borer trap hanging in the tree near my house.

The Minnesota Department of Agriculture was out in my neighborhood yesterday. They put the Emerald Ash Borer “trap” (in the photo at left) in the tree on the boulevard that’s practically right outside my back door. Later in the day I saw another trap hanging from an ash tree along one of our parkways, this one next to the Mississippi River.

The Emerald Ash Borer arrived from Asia as long as a decade ago. It is thought to have been in the wood of a packing crate on board a ship or an airplane.

There are no natural predators of this pest in North America. Since it was first discovered in Michigan in 2002, some thirty million ash trees have succumbed to the disease.

These pests are now known to infect trees from Pennsylvania south to northern Virginia and west to Missouri then north to Minnesota. None have been found in Iowa, but Iowa is surrounded on three sides by infected areas, so it’s just a matter of time. The infestation is into Canada, affecting the provinces of Ontario and Quebec.

Trees infected with this beetle were found in St. Paul earlier this spring and reported by the Minneapolis StarTribune.

Just over a month later, the “traps” are appearing in my neighborhood and all over the metropolitan area. Minnesota has over 900 million ash trees and they make up a third of all trees in our metro area.

The good news is that proactive steps are being taken to hopefully prevent another huge loss of our urban forest, like Dutch Elm Disease did to our trees in the 1970’s.

The US government has established a five year plan to test and develop a possible biological control for this pest. Three insects that are natural enemies of the Emerald Ash Borer have been identified in China. They are stingless wasps that seek out and kill the EAB’s eggs and larvae.

The State of Michigan has approved the release of these natural enemies. A laboratory has been set up in Michigan in which to grow these insects to further study their effectiveness in saving ash trees and how they interact with native organisms. They will also study the effect on non-targeted species (i.e., other trees, insects, etc.).

At the end of the five year study scientists will evaluate which natural enemies are most suitable to mass-produce and release in the wide-ranging areas where the Emerald Ash Borer is known to exist.

Let’s hope it works.

Pine trees rarely need to be pruned, but June is the time to do it.

In Minneapolis today workers hoisted the last steel beam to the top of the new baseball stadium.

Attached to the steel beam was a pine tree.

The tradition goes back some 1200 years to the Vikings, (somehow appropriate). Scandinavian builders topped off their buildings with a sheaf of grain for the horse of their beloved god, Odin. For his part, Odin was so pleased with this that he bestowed good luck on the future occupants.

As the Vikings spread throughout (conquered) Europe, they brought their topping off practice with them. Britons and Germans substituted trees for the grain and interestingly enough, the Scandinavians eventually switched to using a tree.

The tradition was brought to America by Scandinavian iron workers, who promptly added an American flag. Eventually it became common for the workers to sign the beam before it was set in place.

Not only does raising a pine tree commemorate building to the highest point of the structure, it also celebrates doing so without serious injury to the workers.

Pine and evergreen have long symbolized hope to humanity. During the cold, dark, seemingly lifeless days of winter, the pine and evergreen remain green and look alive.

For the most part, pine trees do not need pruning. If you do prune a pine, don’t remove whole branches; the tree may never recover. If a branch is growing into a path, for instance, cut a few inches off the tip rather than the entire branch.

Evergreen shrubs and small trees are often pruned to maintain their size and shape in the landscape. June is the ideal time for this.

Again, prune sparingly. Only prune off the tips of the branches. If it is necessary to remove an entire branch, do not cut it off flush with the main trunk, leave a quarter inch stump.

If you have an large pine or evergreen which has overgrown its space and you’re tempted to cut off the bottom branches, do the tree and yourself a favor and have the tree removed.

Cutting off the lower branches of an evergreen removes the lowest level of support for snow-filled branches. Eventually, starting at the bottom, the remaining branches will break under the weight of the snow.

Remove the tree and plant something that loves acid soil, like blueberries or rhododendrons.

Blueberries taste a lot better than pine cones anyway.

"Leonard Messel" hardy magnolia in bloom.

Magnolia trees conjure up images of genteel southern plantations and live oak draped with Spanish moss. Many northern gardeners aren’t aware of the several hardy varieties of magnolia that will grow and thrive as far north as USDA Zone 4.

I wasn’t aware of this until I saw a potted magnolia seedling (pictured at right) in bloom and for sale at the Farmer’s Market. You can be assured it is hardy in Minnesota and other Zone 4 areas.

The Star Magnolia, Magnolia kobus var stellata, is one of the most common hardy magnolias grown. It is actually a large bush, growing about ten feet tall, with an upright, uniform appearance. Its branches spread out nearly as wide as it is tall and are somewhat tiered. Star Magnolia produces white blooms in late April or early May.

“Leonard Messel” and “Merrill” magnolias are the result of a cross between the tree-like Magnolia kobus and its shrubby variety stellata. They both grow somewhat larger than the Star Magnolia. “Leonard Messel” has delicate, lovely pink blossoms with white inner petals and “Merrill” offers white flowers on an extremely vigorous and large growing tree.

The Cucumber Tree Magnolia, Magnolia acuminata, is so-named in reference to its fruit aggregates, which somewhat resemble cucumbers. This magnolia is grown primarily as a large and beautiful shade tree rather than for its flowers. These trees can grow to eighty feet tall and forty feet wide.

You’ll find potted magnolia trees at the garden center. Magnolias don’t like their roots disturbed so you’ll rarely, if ever, find them for sale as bare root or balled and burlapped plants.  When you get it home, plant it into its final growing place and leave it there.

Plant magnolias in full sun; they’ll grow in light shade, but will produce fewer flowers and exhibit less vigorous growth.

Make sure that the tree gets adequate water the first year after you plant it. Thereafter, it should do nicely fending for itself, although all trees benefit from artificial watering during times of drought.

Magnolia trees often live eighty years or more. What a legacy to leave to your grandchildren and their grandchildren.