Most apple farmers raise dwarf trees because the dwarf trees generally provide a quicker return on investment, produce better quality fruit, require less labor, suffer less disease and are easier to spray. However, dwarf trees have shallow root systems and compete poorly with weeds. Many organic apple growers with dwarf trees rely on wood chip or bark mulch (by-products from local sawmills) to suppress annual weeds around their trees, but over time aggressive perennial weeds such as Canada Thistle can invade the mulched area. Canada Thistle has deep roots and once established it is very difficult to eliminate using organic methods. Repeatedly killing thistle shoots by mowing or other means can deplete thistle’s root reserves and gradually suppress or eliminate it. Unfortunately, this repeated killing is time-consuming and difficult to accomplish on a commercial scale. We will measure the time requirements and effectiveness of four methods of killing Canada thistle shoots in our apple orchard: hand-pulling, spraying with an organic herbicide, mowing with a string trimmer, and cutting shoots off with a hoe. We will evaluate each technique in plots mulched with bark only and in plots mulched with both bark and cardboard.
Project objectives from proposal:
- Compare four methods of repeatedly killing Canada thistle shoots in our mulched apple orchard: hand-pulling, spraying with an organic herbicide, mowing with a string trimmer, and cutting shoots off with a hoe.
- Evaluate each method in plots mulched with bark only and in plots mulched with both cardboard and bark.
- Measure time required and effectiveness at reducing thistle populations for each treatment.
- Share results with other organic apple growers through our website, a field day, emails to grower list-serves, articles in grower publications, and a conference poster session.