Quercus (oak) maintenance

Making the rounds

Before starting my shift as a volunteer at the University of Minnesota Conservatory Greenhouse I enjoy walking around to see what plants are in bloom, and I also check on my prior projects to see how they have progressed over time. Today I noted the corpse plant was in full bloom.

It is a sure sign of spring when the corpse flowers are blooming (Amorphophallus titanum). From the tropical forests of Indonesia, it has one of the largest flowers in nature. When it blooms, the large red and green "flower" spathe may measure up to a meter in diameter. It has a scent similar to rotting flesh, the color is dark red like meat, and the central flower spike (spadix) heats up to body temperature. All of these features are helpful to attract insect pollinators.

Corpse flower (Amorphophallus titanum)

Oaks

There are several species of oak trees (Quercus) in the Conservatory's collection. For a long time 16 of them have been used as part of a research project. Located in a separate small greenhouse, all 16 oaks are to be repatriated to the Conservatory in the future. To do so they first need to be cleaned up, re-staked, and repotted in some cases. 

At some time in the past few months the 16 oak plants were the unintended bystander recipients of a fine spray of white wash. White wash is frequently used by green house managers to coat the greenhouse glass to act as a sunscreen for the plants.  As a result, many of the oak leaves were coated with fine white particles which are unsightly, and the powder is possibly causing the photosynthetic potential of the leaves to be reduced.

My chore for the day was to clean the white wash off the leaves, stake, and repot the trees as needed. In my three-hour volunteer shift I was able to clean and repot three oak plants. I figure the group of 16 oaks will take many more hours to prepare before moving them into the Conservatory. The three species for today were: Quercus douglasii, Quercus chrysolepis, and Quercus aristata.

Oak species waiting to be cleaned

Quercus douglasii is a native of parts of California. It is a large and long-lived tree known for being drought tolerant. It has the common name of blue oak for its leathery blue-green leaves, which have lobated edges. The leaves are deciduous. The pollen of the tree is highly allergenic. The acorns are an important food source for wildlife and livestock.

Quercus douglasii

Quercus chrysolepis, or canyon oak, is an evergreen oak native to western Mexico and the California coast. It also has flat leathery leaves with prominent spines on the leaf edge. It tends to be found along stream beds, hence the name canyon oak.

Quercus chrysolepis

Quercus aristata is another evergreen oak tree native to western Mexico. It grow no taller than 40 feet. It has stiff leathery leaves with sharply serrated edges when mature.

Quercus aristata

The orchids are still flowering this spring.

Cymbidium schroederi, native of China and Vietnam