Hi I have a nice carpet of creeping thymes that i planted in my front yard a few years back and they kust flourished and the flower carpet is beautiful in early summer. I noticed over the past few years grass patches coming up in some areas. Will they invade the creeping thymes or will teh thymes fight the grass out? What can I do to kill the grass in the patches and yet not harm the thymes
There are several species of thyme that we know as a low ground cover or “creeping”, including Thymus praecox. As you describe, it can form a fragrant and attractive dense mat of plants by extending runners above ground, and with purple, pink or white blooms depending on the variety. Thyme is best grown in well draining poor soil (sandy or rocky) and creeping thyme does not require fertilizing. It requires little water, although if grown in well drained soil then occasional watering during dry spells is indicated.
The grass may have grown in from adjacent lawn, from roots or seeds present in the soil, or seeds that blew in. Now that you have patches of grass mixed in, the best way to get rid of those is by pulling them out. Ontario no longer allows the use of cosmetic insecticides/herbicides. Grasses spread by underground root-like stems called rhizomes, so pulling all the root growth is important to get rid of it. Grasses tend to grow and spread well, so the thyme is not likely to outcompete it. For larger affected areas you could dig them up, then plant new plugs of the thyme. Grasses also spread by seeds and if you have a lot of grass weed (that matures to develop seed) nearby then the problem may re-occur. Cutting those grasses before they set seed will be helpful.
You can try to identify the type of grass you are dealing with; I cannot tell from the image. There are several plant ID apps such as Picture This and PlantSnap that may provide an identification from a sharp image. Once you know which type of grass you are dealing with you can search for strategies to control it. Here is a general reference for growing thyme: https://plants.ces.ncsu.edu/plants/thymus-praecox/
Best of luck in preserving your creeping thyme!