Carol Stocker - Globe Correspondent April 6, 2021 5:43 pm What to do this week Take your lawnmower to a hardware store or a small-engine repair shop for service. Sharpened blades mean healthier lawns. Within the next six weeks, patch or overseed lawns to thicken the grass and crowd out weeds — or wait until September. (This is the secret of a good-looking lawn.) Make sure the grass seed stays constantly moist until it sprouts. Pull back mulch from around grafted roses and fertilize them. Prune out dead and crossed stems, cutting them back to just above outward-facing leaflets to encourage an open form so it doesn’t become an ingrown tangle. Clean out old birdhouses and add new ones. Visit the Cornell Lab of Ornithology’s NestWatch website for details on building and siting boxes for local cavity-nesting species, which are in need of homes because few people leave dead trees standing for them to excavate. After a week of 50-degree weather, start your spring cleanup in the areas closest to the house and then work outward to where the bulbs are sprouting or early vegetables will be planted. If possible, leave property edges and woodlands natural and undisturbed. Leaving “wild’’ areas to explore is good for children, too. Pick a compost pile site for dumping garden debris if you don’t already have one, and also designate a separate pile for last year’s leaves, which will crumble into a nutrient-rich and weedless mulch in a few months. If you need finished compost for your garden immediately, try to have it delivered in bulk rather than hauling individual bags home. If you are growing vegetables, label and file your seed packets in order of planting date, counting back from the date of the last frost in your area, which is often May 1 in Boston but later in the month in colder areas. Repeat sowings at two-week intervals as insurance against late frosts and also having to harvest too many vegetables at once. You can start sowing or transplanting peas, radishes, turnips, parsnips, onions, arugula, kale, lettuce, carrots, cilantro, dill, and spinach outdoors now in most of southern New England. But seeds may rot if the soil is below 40 degrees, so a soil thermometer is a good investment. Cover tender sprouted seedlings with lightweight sheets or spun polyester on frosty nights.