I have several patches of some weed, which looks like grass or sedge and grows much faster than regular grass, has wide flat leaves and spreads quickly. I wonder which weed is this and how to try to eliminate it. One can see on the attached image how higher and wider the leaves are than the rest of the grass. Thank you very much
Thank you for contacting the Toronto Master Gardeners about the grass-like weed that is growing in your grass. I can’t be sure from your picture but I think this is quackgrass (Elytrigia repens or Elymus repens, previously called Agropyron repens). It is very difficult to get rid of. For definitive identification, look for these two characteristics: the first is clasping auricles. Auricles are tiny plant structures at the base of the leaf blade where the leaf blade connects to the stem. In quackgrass these auricles look like little claws that grasp around the stem. There is a picture of this in the link at the end of this response. The second thing to look at is the roots. Quackgrass has rhizomes which are underground stems that grow horizontally very quickly and have nodes every few inches that send up shoots and send down very fine fibrous roots to form new plants. The rhizomes are straw-coloured to white and have sharp tips.
Quackgrass is a long-lived perennial that spreads aggressively via mats of rhizomes and also propagates by seeds. It is self-sterile and mainly propagated by wind. It is a cool season grass that grows vigorously in the spring (when it sends up new shoots) and fall (when it stores sugar it its roots and rhizomes to help it survive the winter). It flowers in late June – July and the seeds mature in August – September. Seeds drop in late September and overwinter in leaf litter or on the ground. They can remain viable for 1-6 years.
The best defense against quackgrass is a dense, strong and healthy lawn. Proper lawn culture including an appropriate fertilization program can help to keep quackgrass out. Also, quackgrass does not tolerate shade.
The main reason that quackgrass is so difficult to eradicate is its rhizomes. For a small patch you can try hand-pulling when the soil is moist but rhizomes can break and you need to get every fragment or the plant will grow back. Careful monitoring and repeated hand-pulling before the plants have four leaves will be required and can be successful after several attempts. Note that quackgrass has also been shown to be allelopathic, meaning that it releases chemicals that inhibit the growth of other plants. These chemicals can be released after plants have been pulled if they are left on the ground.
You could also try tarping to get rid of quackgrass, meaning covering it with a black / light-blocking tarp throughout the entire growing season. If you want to try this, it is suggested that when it’s time to replant you could consider sod as the replacement instead of grass seed. Any remaining bits of rhizome will have difficulty penetrating the sod.
Another approach is to live with the quackgrass. Mowing it will help it to blend in with other grass. Mowing your lawn closer to the ground will help to reduce new rhizome growth in the quackgrass.
There is additional information about quackgrass at this link from Oregon State University. Please note that the information about pesticides (chemical controls) in this article applies in the US and not in Canada. The use of pesticides in Ontario for cosmetic purposes in home lawns and gardens is strictly controlled by law. This link contains an Allowable List of active ingredients that can be used in Ontario.
Assuming that you do have quackgrass, hopefully this information is helpful as you consider your options for dealing with it.