I planted a fall cover crop last fall to loosen up our compacted yard in Sacramento, California. Currently, it's very tall, like 3 feet, and I'd like to mow it soon. But it contains winter and annual rye that has not yet gone to flower. Everything I read says wait for these species to flower before mowing.
I'm getting some seedlings ready to put in the ground and I'm wondering if there would be detrimental effects if I go ahead and mow the cover crop before it flowers?
If depends what your future plans are. If you let the rye seed, you will get a following crop of rye whether you want it or not. If this was a one-time "green manure" crop, I would say mow it and kill the roots (with herbicide) before it seeds.
On the other hand if you want to convert your yard into a permanent hay meadow, then you should let it seed before mowing. There's no point buying more seed when you are growing your own for free!
Normally you don't want a cover crop to go to seed. One of hte ways to de-weed a field here is to plant a succession of annual crops -- buckwheat, field peas, and annual rye, mowing each at the end of flower set, allowing the clippings to dry, then tilling in. This creates another flush of weeds. Harrow, and start the next crop. The annual rye doesn't have time to seed. Mow it and leave it in place as erosion control for the winter.
Thank you both very much! I appreciate you offering your expertise. There's so much information to sift through when starting a first garden from compacted clay soil! We're planning to use it as green manure, so the time is nigh to mow.