By Sara Fitzsimmons
Soil and weeds will significantly and negatively affect the growth of young trees; grasses in old fields are especially tough competitors. Growers with most success keep a weed-free area of at least 2-3 feet in diameter around their trees. The following article details several alternative approaches we at at Penn State have seen (though not necessarily used) implemented for weed control. The article also has a poll to determine what you the audience feel is the best approach for weed control. Come back often to see how your fellow tree growers feel about the subject.
You can mow, mulch, use a tarp or other plastic wrap, or spray with herbicide in order to manage within row vegetative competition. Some growers prefer to use organic options of weed control, while others do not have this constraint. Between rows, PA-TACF encourages growers to control vegetation through mowing, as this will help control rodent populations within the orchard. Also,
when tree shelters are employed, hand weeding within the tube will be necessary to control vegetation directly against young trees, at least for the first two years.
ORGANIC OPTIONS
For a grower who strives to keep their land organically certified, the options for weed control include
landscape fabric, black plastic mulch, cardboard, and even corn gluten. Generally, landscape fabric and plastic mulch are favored. Wood chip mulch may be applied over landscape fabric or cardboard to halt deterioration of the materials
- Be careful with wood chip and black plastic mulch, particularly if you have not protected the stem with a tree shelter. Rodents, most often voles, like to live within or under mulch, just waiting for a vulnerable chestnut tree on which to munch.
- Black plastic mulch is not permeable. Depending on the type of irrigation and fertilization method you choose, black plastic mulch may not be the way to go. Broadcasted granular herbicide will not be able to sink in through the plastic. You will need to water the trees individually with a liquid-based fertilizer, or use a drip-line irrigation system into which you inject a liquid-based fertilizer.
- Landscape fabric is permeable, but often more expensive. Weigh the costs and benefits, and feel free to consult with the Chapter's tree breeding program coordinator.
- Organic herbicide? Some gardener magazines suggest the application of a cocktail of lemon juice and vinegar to control offensive competing
vegetation. Corn gluten is another option. The effects of these methods on chestnut culture have not yet been fully evaluated by the Chapter. Use at your own risk!
NON-ORGANIC OPTIONS
The most often employed method of weed control by PA-TACF growers is through the use of commercially available herbicides. Although we do not officially endorse the use of any one herbicide, most growers use RoundUp or a similarly-formulated broad-spectrum herbicide. There are many generic brands of glyphosphate-based herbicides — check around for different brands. In general, however, check the concentration, read the label well, and get a brand with an included surfactant, which will help the herbicide stick to the vegetation better.
- Spray when the weather is clear and the target vegetation is actively growing.
- Spray about 2 times per year, once in the early summer and once in the fall.
- Keep an area 2-3 feet in diameter around your trees free of grass and weeds.
- Be certain to protect the bark and leaves of the chestnut tree — 2 foot tall plastic tree shelters work very well for this.
- *Always* read the label and follow instructions on the herbicide. Unless you are fully certified and trained to work with herbicides, consult with your local extension agent and breeding coordinator before embarking on a killing spree with a potentially dangerous herbicide cocktail.
There are other herbicides out there that work differently and have more specific targets than RoundUp. These include chemicals specific to woodyvegetation or pre-emergent herbicides. Typically, these chemicals require certification or extensive personal protective equipment (PPE) for application.
Sara Fern Fitzsimmons
Northern Appalachian Regional Science Coordinator
The American Chestnut Foundation
The Pennsylvania State University
206 Forest Resources Lab
University Park, PA 16802
e-mail: gro.fca@aras
phone (office): 814-863-7192
phone (cell): 814-404-6013
fax: 814-863-3600
http://chestnut.cas.psu.edu
https://tacf.org
http://www.pattacf.org
