My wife and I recently purchased a house in East York (Toronto) and decided to remove the turf in our front lawn and plant a wildflower garden. We removed all of the grass in late spring, tilled the soul multiple times over a couple weeks, added some compost and soil and sowed the seed, of which most was local and high quality. For a month all was great, flowers and all, but one week away on vacation (mid August) and we came back to a mess; what looked like crab grass had sprouted everywhere. We gave up and did little to maintain the garden after that point, but we now would like to know what we should do to prepare the garden for winter and what methods we can use to prevent the weed from establishing itself next year.
North facing garden – sun all day
Looks like weed has gone to seed
We did not trim any part of the garden
Thanks so much for your help!
Crab grass is an annoying weed for which there is little we can do other than pulling it out when it is seen. The action of tilling your soil and adding compost prior to sowing seeds probably exacerbated the problem. Crab grass seed (as with many seed types) can lay dormant for some time before they sprout. They are so pervasive and are readily spread by wind, birds and animals. Unless the soil in which you plant is sterilized, you can easily have crab grass. Allowing the grass to remain in your garden and allowing it to go to seed should be avoided as that seed will readily sprout next summer. Given that your garden is in a sunny location and watered daily, those are the perfect conditions for crabgrass to flourish.
A heavy layer of mulch can be used to keep crab grass down but that can also prevent the sprouting of your wildflowers. Similarly, a layer of landscape fabric can keep the weeds down but will prevent any wildflowers from sprouting. Thankfully, crab grass sprouts later than many plants so you may have time to lay down mulch after the wildflowers sprout and before the crab grass does. Their roots are also very shallow and should be easy to pull.
There is no easy answer to the crabgrass problem other that to either mulch and/or pull the crabgrass as it sprouts. They are an annual weed so they will die with the winter kill but the seeds remain dormant through the winter and will sprout in mid-spring to mid-summer next year when you will have the opportunity to deal with them if you keep up with mulching and pulling the crabgrass out as it sprouts.