Weed control for perennial bulbs
I own a small cut-flower Farm in the Upper Peninsula. I’m having difficulty determining what to use for weed control in my perennial (monocot) bulb beds (Daffodil, Leucojum, Alliums). We grow the plants in rows in 100 sq. ft. raised beds. Our primary weeds are clover and quackgrass. I have access to several types of mulch (I.e. pine needles, sawdust, straw). We use black plastic film with our other perennial plants that we gradually rip out as the plants spread and expand. Any ideas of what might work best to avoid or reduce hand weeding would be appreciated. Thank you, Beth Scafone WellSpring Farm
Unfortunately, there are very few herbicides labeled for use within ornamental bulb crops and most are preemergence type products that would target annuals emerging from seed. A directed application/spot treatment may be an option, but great care would be needed to avoid contacting the ornamentals. There is a gel formulation of glyphosate called Roundup Precision Gel that may help keep it on target. If you remove the bulbs during the winter you may be able to do a late-season application of a broadspectrum herbicide like glyphosate that could knock the population back. Fall applications are most effective at reducing herbaceous perennial populations, but the air temperatures need to be consistently over 50F. As with any pesticide application, be sure to read and follow all labeled instructions.
As far as other methods, the black plastic mulch that you move over time may help, but the rhizomes of quackgrass are pretty hardy. Cover crops have also shown some reduction in quackgrass populations, however, this is most appropriate for annual systems...and you may also be limited on growing degree days to make this successful.