Thursday, May 5, 2011

Do Baked Potatoes Grow on Trees?

If you've taken a close look at Seeds Farm lately you may have noticed some shiny "decorations" on some of the trees. A number of our trees--mulberry, fig, guava and pomegranate--have what appear to be foil-wrapped baked potatoes skewered onto their branches. In actuality, these trees are being propagated by a technique known as air layering.

As part of Paul Maschka's Organic Fruit Tree Care class offered here at City College, students have had the opportunity to practice pruning, grafting and propagation techniques on the Seeds Farm fruit trees. While many students in the class were familiar with the concept of grafting trees, air layering proved to be a new technique for most.

Air layering is typically started in Spring on a pencil-sized diameter branch, which has grown within the last year. From this branch a clone of the mother tree will be created.

The first step in the air layering process is to girdle or wound a 1 to 1 1/2 inch wide section of the branch, cutting through and removing its outer layers of bark, cambium, and phloem. One has to be careful not to cut too deeply because the xylem layer which transports water and nutrients to the future clone must be left intact.

The girdled area is then wrapped in a series of layers that act somewhat like an aerial pot. The first layer consists of very damp sphagnum moss--the medium in which the clone's roots will grow. The next layer is plastic wrap which holds the moss in place, retains moisture and serves as a window to view whether the clone is successfully rooting. Aluminum foil, the final layer, reflects sunlight and keeps the moss packet a cool and inviting place for new root growth. Snuggled in an optimal environment--dark, moist and mossy--the girdled area of the branch is stimulated to form a callus from which grow buds are able to develop new roots.

The rooting process requires patience on the part of the propagator since it can take from a few months to a year before the branch grows a hearty enough root system that allows it to be removed safely from the parent plant, potted and eventually thrive on its own.

If the students' endeavors prove successful, Seeds Farm will eventually have a number of new baby trees that are genetic clones of their parents. Because so little material is required, air layering promises to be a cost-effective way of propagating trees.

No comments:

Post a Comment