A water oak is a deciduous tree with a comparatively short life span. It is a member of the red oak family; the botanical name of this tree is Quercus nigra. Native to the U.S., the water oak can grow in any soil type and has small leaves in comparison with many other oak types. It is prone to limb breakage and early death, meaning it is not always a popular specimen for home gardeners. This species produces seed every other year.
Growing to about 80 feet (24 meters) tall, the water oak develops pronounced ridges on the bark as it matures. This species drops its leaves every autumn, although a few leaves may cling on to the branches through mid winter, causing it to sometimes be described as tardily deciduous. New foliage develops in early to mid spring. As the leaves mature, this species produces masses of very small, inconspicuous flowers which are followed by an abundance of acorns.
The acorns of the water oak are small and have a squashed appearance. Like all other oak species, the acorns are the seeds. The acorns of this species remain on the tree for two years, and the tree only produces seed every other year. Taking two years to mature, the acorns are eaten by a number of birds directly off the tree. The seeds that fall are consumed by a large number of foraging animals and insects.
After laying on the ground and exposed to harsh winter conditions, the healthy acorns will then begin to germinate. It is common for the water oak to cross-pollinate with other red oak species, thus creating hybrid oak trees. These crossbred trees are first generation hybrids which in turn create second generation hybrids that usually perform poorly, exhibiting many negative traits from the original parent trees.
Tolerant of any soil type, the water oak will not abide by constant water logging or prolonged periods of drought. Like many oaks, this species has a large, complex root system which enables it to survive in nutrient poor soils. The far reaching roots are able to extract the required nutrients from a wide area.
This species is prone to a number of cankers, galls, and root rots, particularly if a tree already suffers from poor general health. Root rot is more likely to attack trees which are exposed to prolonged periods of water logging. The presence of extensive root rot can lead to the early death of the tree and in extreme cases can cause the water oak to fall. Severe canker and gall infections can lead to limb breakage.
With a comparatively short life span of around 70 years, it is not uncommon for the water oak to die at 40 years. This means that by the time the tree approaches its full height, it is close to the end of its life. Therefore this species is seldom recommended for growing in gardens or close to houses.