May is a good month to work on your lawn. Rake to remove dead grass, top-dress bare areas with a mix of topsoil and peat, then reseed. Use a quality grass seed mix containing Kentucky bluegrass, red fescue, and perennial ryegrass. Water seeded areas, keeping them moist as the grass starts to grow.
Mulch Now or Forever Hoe Your Weeds
Apply mulches now, while the soil is still damp, to help retain moisture and to keep weed seeds from germinating. Two to three inches of any organic mulch is usually sufficient enough to discourage even the most persistent weed seeds.
Keep Container Plants Happy
Container-grown vegetables and flowers can dry out quickly, especially on a concrete patio in full sun. Daily watering may be necessary as the season progresses. To check for moisture, feel the soil in containers at least once a day. Water when the soil is dry down to a few inches. Apply water until it runs out of the drainage holes. Every 2 to 3 weeks, immerse each container in a larger container of water to force out air pockets and thoroughly moisten the root mass.
Harden Off Tender Plants
Begin hardening off tender vegetables, herbs, perennials, and annual flowers that you've started indoors. Start by placing them in a shaded, sheltered location for the day and bringing them in at night. Every few days select a sunnier, windier spot until the end of the last week of May when it is finally safe to plant most things outdoors.
Plant Summer-Flowering Bulbs
Cannas, caladiums, and tuberous begonia bulbs can be planted now. Choose a well-drained and partially shaded area, and set the tubers in the ground so they are barely covered. Place them 18 to 24 inches apart to allow plenty of space for growth and good air circulation. Water in the morning or early afternoon to give the foliage time to dry before nightfall and you'll reduce the chances of disease.