Adding Mulch to Suppress Weed Seedlings! We have been having a problem with continuous flushes of seedling weeds, including grasses, purslane, pigweed, mallow, and many others. As soon as we pull one flush, another flush germinates. At the same time, we are expecting some very hot, dry weather later in the summer, so we know we will need to conserve moisture. Our answer is to put about an inch of some fine organic mulch in a layer around the base of our seedlings and transplants. We are expecting this mulch to withhold enough light so the weed seed will not germinate. At the same time this mulch will create an insulation barrier to reduce the moisture evaporation from the soil surface surrounding our plants. Our irrigation trickle tube is located under the mulch, so the soil should absorb the irrigation water without disturbing the mulch. A weed that will outsmart this system will be yellow or purple nutsedge, which will grow right through the organic mulch and sometimes through the landscape fabric mulch we also have in place. The best way to eliminate the nutsedge in a small garden is to just keep pulling it, so that the “nut” tuber growth is suppressed or eliminated. The fight goes on! We expect to win!!