Pittsfield Charter Twp, Michigan

Visitors to the township offices may see work underway on the parking lot island in front of the main entrance. Originally built on top of gravel and packed clay, mostly covered with a concrete sidewalk, the island was unfriendly to living things.

The gardening staff removed most of the gravel and replaced it with soil and compost. But a challenge remained—finding a tree to plant there that could withstand extremes of standing water, drought, and heat from the surrounding asphalt.

Thanks to the generosity of Dr. Bruce Hannon of the University of Illinois, a bur oak seedling now grows on the island. Once its tap root is established, it will grow up to 30 feet in the next 15 years. Since 1971, Dr. Hannon has collected acorns and germinated them for bur oak adopters, in a project to conserve these once-plentiful trees of the midwest.

The Bur Oak, a suitable gift to the future.

By Dr. Bruce Hannon

University of Illinois, Urbana-Champaign
"The Ikenberry Project"

A member of the White Oak group, Quercus Macrocarpa grows 70 to 80 feet tall with a trunk that reaches 2 to 3 feet in diameter. The Bur Oak, which can live to be 150+ years old, prefers bottomland forests and the open edges of the upland forests in the region of Ohio, Michigan, Indiana, Illinois, Wisconsin, Minnesota, the Dakotas, Iowa, Missouri and the lower Mississippi River region.

The Bur Oak was the most likely tree to find in the prairie Savannah, that space between the pure prairie and the forest. The fires burned everywhere the soil was not wet. Forests grew along the streams and rivers and the prairie covered the rest, except for these intermediate areas, the Savannas. Here the soil was sometimes moist, abating the power of the fire. The Bur Oak bark offers better fire protection than all but the Cottonwood and the acorns are heavily insulated. The original land surveyors, who walked this area in 1820-1, often referenced their section posts to nearby oaks. Some of these "witness" trees can still be found.

The tree grew almost exclusively and alone (of the trees) in the prairie savanna, that area between the full, treeless prairie and the water-feature protected full woods. The prairie burned every 3-5 years and the full woods burned every 30 or so years, with the never-burned areas, those downwind of the larger, permanent water bodies being the only place where the Sugar Maples could survive. The savanna burned with a frequency somewhere between the two adjacent areas. So on the tall grass prairie, the savannas were Bur Oak groves, with these trees aging up to 300+ years. The tree survived the fires due to its heavy bark and its well insulated acorns. We have some examples of such groves not far from Urbana-Champaign. The fires on the prairie were started by lightning and by the Indians, who herded the buffalo with fire and found that the lush prairie after the fire favored small game.

The Bur Oak can grow quickly in sunny, well-watered areas of the urban lawn, reaching a height of 30 feet with a trunk of 4 to 5 inches in diameter in only 15 years. The wood is strong and therefore the tree is clean and safe to plant for shade of the home. The large acorns, which become abundant in about the tenth year, are a definite attraction to squirrels, so few will naturally ripen for planting until the tree is very large.

To grow a Bur Oak from an acorn, pick the acorn from the tree or ground as late as possible, probably in late September or early October. Leal Park, in Urbana, has several very large Bur Oak trees. Some years, specific trees have no acorns. Some years, all Bur Oaks in the region have no acorns. Let the acorn dry for a few weeks until the husk turns brown. Too-rapid drying will cause damaging cracks in the husk. Remove the cap carefully and place the seed in a glass of water. If it sinks, the seed is sound. If it floats, the seed has been riddled with worms and will not likely grow. Acorns that lie on the ground are likely to contain worms. Plant the seed in a standard pot about 6 inches in diameter and 8 inches deep filled with the native soil enriched with organic matter. Keep the soil moist but well drained. I water them every other week, very lightly. The seed should germinate in a few weeks and appear in the first 1 to 3 months, reaching a height of 6 to 12 inches by March or April. Plant the seedling in the spring to prevent its roots from filling the pot. If you cannot plant the tree until fall, carefully transplant the entire contents, intact, to a larger pot (12 to 18 inches in diameter and deep). Keep the plant in strong sunlight and well watered throughout the summer.

Choosing the best place to plant a tree for the next 150 years is quite a problem. Look over your lot in the context of your neighborhood. Imagine someone plotting to expand it into an apartment or to add an extension or garage. Check for the possibility of street expansion or extension. Don't plant the seedling within 8, preferably 10 feet of a building or concrete slab. Locate your sewers, water and gas lines. Look out for overhead wiring. Think of the Utility Companies trenching through your property. Remember that the drip line of a tree (its shadow from a directly overhead sun) is the approximate horizontal extent of its root system.

The leaves of the spring transplant may fall immediately due to the shock of the new soil. They should re-grow by June or July. Growth of the tree is very slow at first. The seedling needs protection from accidental mowing or stepping. Surround the seedling with a white wire fence, about a foot in diameter and a foot high, and stake it to the ground. The fence serves as a marker and reminder and it keeps rabbits from cutting the bark in winter.

The leaves may turn light green for a while. This is a sign of a lack of iron and it comes from the slightly alkaline condition of the Central Illinois soil. The Bur Oak, unlike the Pin Oak, has adapted to our soils and so the iron shortage should not continue. Some say that a continued light dosing of sulfur over the root zone, followed by watering, will stop the iron anemia.

As the seedling grows, prune the lower branches (in the early years, the lower leaves). Don't let the tree develop a major fork. If several major sprouts arise from its top, choose the stronger or larger and cleanly cut away the rest. Prune the tree whenever you wish - don't worry about covering the wound. Prune carefully - don't tear the bark. Cut the branches close to the trunk so that the bark can easily grow over the wound. Due to the absence of insects, autumn is slightly the better pruning time. Keep up the pruning of the lower branches to at least 10 to 20 feet above ground. This simulates the effect of the prairie fires. Never remove more than about 10 to 15% of foliage in any one season. If the tree grows in a slight curve, don't worry. It is probably maximizing its exposure to sunlight and it will straighten as it gets larger. Curved growth will occur when the seedling is planted close to another, much larger tree. If you must transplant the tree, make the root ball at least 10 times the diameter of the trunk. Retain the same solar orientation.