No tree symbolizes strength and longevity more than the mighty oak. Oaks are at the pinnacle of ecological value. With over 90 different species in North America and about 435 worldwide, Quercus has the most species in a tree genus in the Northern Hemisphere. Consisting primarily of large and long-lived trees, Quercus is a true force to be reckoned with.
Oaks support more insects than any other North American tree genus, with almost 900 different species of caterpillars in the United States alone. In comparison, the Maple genus, Acer, interacts with around 300 caterpillar species.
We pride ourselves on the quality of our oak trees. All of our native oaks are a local ecotype and grown from acorns. We meticulously source our acorns from specific parent plants that produce seedlings with specific desirable qualities, such as vigor, tolerance to alkalinity, or germination percentage.
We also take measures to improve the quality of our oak root systems by root pruning in various stages over the seedlings' early life. Our root culturing reduces the dominant taproot and replaces it with an extremely dense and fibrous root mass with loads of horizontal shoots. This process gives us an oak with a shorter establishment period and the ability to be transplanted with ease.
In addition to root culturing, we also put our seedlings through a strict grading process. We cull any inferior seedlings that don’t meet our criteria for being passed onwards. This grading gauntlet ensures every oak that makes it up to the target sale size is up to our standards.
Oaks are at the pinnacle of wildlife value. There are several factors contributing to the overwhelming impact of Oaks in our ecosystems. Along with caterpillars, they also host many other insect species such as beetles and arthropods. These insects all like to feed on the foliage and other parts of the tree. It should be noted that these insects rarely cause damage to the point of needing treatment.
These various insects draw in insectivorous birds like Warblers and Tanagers. The fruit of the oak is their signature acorn, relied upon by a variety of wildlife species. The acorn is a key component to the winter diet of many birds, like blue jays and woodpeckers.
Oaks are split into two different groups, the Red Oak Group, and the White Oak Group. In general, the white oaks produce leaves that have rounded lobes whereas red oaks generally produce leaves with pointed lobes. The acorns in the White Oak Group have less tannin in their acorns than members of the Red Oak Group. This means that the acorns in the White Oak Group are less bitter and are seen as a tastier snack to wildlife. More than 180 different kinds of birds and mammals use acorns as food, including turkey, duck, crows, quail, mice, and chipmunks.
While many oaks share similar qualities, the plethora of species and cultivars have unique characteristics as well.
At a glance, members of the Red Oak Group that we carry are the Hill’s Oak, Red Oak, and the Black Oak. The members of the White Oak Group that you can find here at Johnson’s Nursery are the White Oak, Bur Oak, Swamp White Oak, Chinkapin Oak, and the Hybrid Swamp x Bur Oak.
The English Oak is the iconic oak of England. Quercus robur has a long and extensive history in Europe and has been present in North America since the 1600s. The masts of sailing ships that brought the pilgrims from Europe were made of English Oak.
Thanks to the centuries of horticultural studies done by the English, there is much known about the species and much that can be applied to our native growing oaks. There are many hybrid oak cultivars that have English Oak heritage. The English Oak has desirable traits that we wish to pass on to our native oak trees. Some of these traits include a desirable form, such as upright or columnar, as well as their high tolerance to alkaline soils.
The underside of the English Oak is their high susceptibility to the two-lined chestnut borer. They're also considered marginally hardy in much of Wisconsin. There are few long-term studies that compare the wildlife value of English Oak to our Wisconsin native oaks. So far, only observation shows that native Wisconsin oaks have more wildlife value compared to English Oaks. If your goal is to support wildlife, plant a Wisconsin native oak. It should be noted that we do not recommend using English Oak or its hybrids in woodland settings or in other naturalized areas to avoid contaminating the native oak gene pool.