Bur Oak

Description:

This Bur oak is located in the Olds College botanical garden and wetlands. It stands alone on the west side of a stand of Bur oaks. This particular tree still has its leaves, while the other oaks do not. According to Canadiantreetours.org, this is normal. The color of the leaves is also normal for fall. The bark is rough, dark grey and furrowed. According to Natural Resources Canada this is ideal. Insects that attack this tree are gypsy moth, fall and spring cankerworm, pale winged grey and two lined chestnut borer. Out of these, only the fall and spring cankerworm, pale winged grey, and two lined chestnut borer occur in Alberta. There is no sign of insects at this time of year. The leaves appear to not be damaged by holes, nor are they missing leaf tissue leaving only the veins. The bark appears healthy, and the twig ends are intact. The most common disease is oak wilt. According to Ontario's invading species awareness program, it is a fungal pathogen but is not yet present in Canada. Monitoring for this disease in Canada is encouraged. The Society of Ontario Nut Growers mentions that the Bur oak is quite disease resistant. Oak galls and shredded leaves are the main concern. This tree appears healthy. Some of the leaves are shredded, this could be from the lack of protection from harsh winds. There also appears to be a fungal issue on some of the leaves, but it is affecting less than 10% of the tree. They are blob like and fuzzy in appearance and yellow to brown in colour. They appear to be galls according to Iowa State University and they do not harm the plant. Looking at pictures on this website, Woolly oak leaf gall may be the culprit. It is the only fuzzy, yellow gall listed. Therefore, I would recommend that the tree be left alone. Leaves could be raked up in the fall, but there is no cure for galls according to Iowa State University. According to the Society of Ontario Nut Growers, younger trees should be kept free of weeds for a minimum of one square meter. The mulch would help with this, as well as with SONG's recommendation to use it. Fertilizer should be used in the spring for trees over a year old. Pruning is also advised for general health and vigour. This is done after the spring sap run is over to avoid sap bleeding.

Habitat:

The ideal habitat for the Bur oak is deep, rich bottomlands. Upland limestone soils and grasslands are also mentioned. Shallow soils over granitic bedrock is tolerated at the northern limits of its range. It also tolerates urban sites. It is moderately shade tolerant And ranges from Southern Saskatchewan east to New Brunswick. The habitat here is further east than the range mentioned, but there are a number of Bur oaks on campus and in town. One in town is designated a heritage tree; it is just over a century old. Therefore, it would seem that these trees survive well here. The Bur oak I am observing stands away from the other trees, exposing it to greater, harsh winds. There is a decent bed of mulch for this tree, which would keep water from evaporating in summer, and help insulate the soil and roots in winter.

Notes:

Websites of note: Iowa State University has information on oak galls at ipm.iastate.edu. Species profile of the Bur oak at the Ontario Society of Nut Growers: songonline.ca. This site gives good general information including pest and disease issues. Canadiantreetours.org. This website has information about the bur oak for identification and what a healthy specimen looks like. Natural Resources Canada has insect and diseases at tidcf.nrcan.gc.ca. Ontario's invading species awareness program lists invading species data at invadingspecies.com.