The Myth and Reality of Native Oaks
by Connor Shaw

Red Oaks (Erythrobalanus) Species include:  Quercus coccinia* (scarlet),  Q. imbricaria (shingle),  Q. palustris (pin),  Q. rubra (Northern red),  Q. velutina (black) * Includes Q. ellipsoidalis  (Hill's or Northern pin) Leaves with the veins usually running out beyond the margin in the form of a bristle Stamens 4 in each floret Cup scales rather thin Inner surface of the acorn shell lined with woolly hairs Fruit in the first year minute ("baby acorns"), maturing the second year Acorns require cold treatment prior to germination White Oaks (Lepidobalanus) Species include:  Quercus alba (Eastern white),  Q. bicolor (swamp white),  Q. macrocarpa (bur),  Q. muhlenberg (Chinquapin) Leaves never with the veins extending beyond the margin in the form of bristles Stamens 6 to 8 Cup scales more or less woody, and knobby at the base Inner surface of the acorn shell smooth Fruit maturing the first year Acorns may germinate immediately after ripening

Oaks are the most underutilized shade trees in our urban landscape even though they compose the largest number of shade tree species in northeastern Illinois. There are nine species of oaks native to Illinois. These nine species are equally divided into two sub-families, red and white oak.

The oaks fit into nearly every ecological niche that occurs. Why are oaks so seldom used, even though they seem to be well adapted to our urban setting? The real answer is multi-faceted and includes myths, survival in the landscape, production difficulties and demand.

Myth #1: Oaks Grow Slowly

Myth Number 1 is that oaks are slow growing. While they are somewhat slower growing than birches, green ash, and catalpa, an oak that has recovered from transplant shock and is mulched should grow an average of 24 inches per year. Oaks produce two shoots of growth per growing season. One shoot will occur in the spring and the second in mid summer.

Myth #2: Move Oaks Only in Spring

Another myth is that oaks can only be transplanted in the spring. We have transplanted thousands of oaks in spring (March to mid May) and late summer/fall (July through November). Our losses have been between one to eight percent. Our trees are grown in root bags for spring and fall transplanting. An above ground container is used for summer planting.

Possibility Place Nursery is conducting a long term study at a local country club in conjunction with Western Illinois University. This study indicates that August may be the best time to plant. Oaks planted in August have two months to grow roots into the surrounding soil. The following year the oaks show very little signs of transplant shock.

A word of caution must be noted on transplanting large oaks. Oaks with calipers larger than 2.5 inches seem to transplant poorly and losses can be very high. 1.5" and 2" caliper trees transplant best. Larger oaks have large diameter roots which do not seem to regenerate. We are currently working with a variety of methods in hopes of solving this problem.

From my own experiences, I have seen the dramatic difference caliper can make on transplant survival rate. We planted 3.5" and 1.75" caliper bur oaks in our backyard. The 3.5" caliper tree grew 8 inches in four years. The smaller oak grew 8 feet during the same period. Larger trees do poorly and take significantly longer to recover from transplant shock.

Myth #3: Oaks Dislike Urban Soils

A third myth is that oaks are not durable in the urban landscape. I have heard this comment from homeowners who have moved into an oak woods with a new house. The existing trees ultimately dies. Construction generally kills most of the roots by filling, compacting and drainage changes. Not many of us would survive if we were prevented from taking in water and nutrients. It is amazing that some of these oaks do survive.

The truth is that oaks are very durable when planted in the urban landscape; many are in fact pioneer species. A pioneer species is found in the early stage of succession. The plants generally grow in full sun and tolerate highly variable soil moisture and nutrients. Bur oak (Quercus macrocarpa) was one of the first trees to invade a prairie. The bur oak had to adapt to severe growing conditions and survive prairie fires. In many ways our urban sites are very similar to the prairie, minus the fire.

Production difficulties do exist in the nursery industry. The majority of shade trees for northern Illinois nurseries are shipped bare root from the west coast. Many of our oaks do not do well with this system. When we purchased bur oak bare root, we lost 30 to 50 percent of the trees. Trees which are difficult to establish are now being produced in containers. These trees have shown a good survival rate once transplanted into the field.

Harvesting oaks with a tree spade can also be a problem. Swamp white oak (Quercus bicolor) and pin oak (Quercus palustris) have very fibrous root systems. Because of this, they are easily dug with a tree spade. The remaining oaks tend to be coarsely branched and have a well defined tap root. I have seen several bur oak dug with a tree spade. The spade lifted the ball as the tree remained stationery. The spaded ball ripped off roots and branches as it traveled up the trunk. The end result is a non-saleable tree.

Urban areas built in the last 25 years tend to be hotter and dryer than normal in comparison to an undisturbed site. Oaks grown on urban soils must adapt to these harsh conditions. A solution to this problem is to plant trees grown from "native" acorns; in other words, from oaks growing within 200 miles west of Chicago. Oaks grown from seed locally are more adapted to our urban sites than seed collected east of Illinois.

Oaks should be used more frequently in our urban areas, but we must educate both the public and the industry with regards to oaks. New methods of production include pot, root bags, copper treated containers and above ground containers. As more and more of these systems are utilized, we will see a dramatic increase in oak planting success for the customer.

This article was published in The Weedpatch Gazette, Winter 2000.