Weeds are a persistent problem in greenhouses, hoop houses, propagation houses and other enclosed structures. Hairy bittercress (Cardamine hirsuta), yellow woodsorrel (Oxalis stricta), spotted spurge (Euphorbia maculata) and liverwort (Marchantia polymorpha) are some of the most common weeds that are found in these structures. Weeds can be found growing within the containers of stock plants, liners and finished plants, in container drain holes, under benches and near walkways within the structures. Weeds growing within the containers compete with crops for space, nutrients, water, light and oxygen, thereby reducing the overall growth and market value.
Any weeds growing within the structure can also harbor pests and diseases. Pest examples include insects such as whitefly and thrips, and other pests such as mites, slugs and snails. Bittercress and woodsorrel are known to be hosts for impatiens necrotic spot virus and tobacco spotted wilt virus, which may be vectored to susceptible host crops by thrips.
For these reasons, it is important to regularly scout and manage weeds. In the first part of an article series from Michigan State University, they discuss some of the effective non-chemical methods for weed control that can be applied inside greenhouses and other enclosed structures.
Non-chemical weed control strategies can be laborious, time consuming and expensive, therefore the last article in the series discusses chemical control strategies as well as currently available products for effective weed control in these environments.