There is no better resource than the Farmer’s Almanac!
Weed perennial beds with special care to avoid pulling up precious self-sown seedlings. When you can tell for sure what’s what, pull the weeds and top-dress the plants with compost or rich soil — just before a rain, if possible.
Provide support for flowers that need it before they start to fall over. Try twiggy prunings or pea stakes for sweet peas and ramblers. Put Grow-thru rings in place for bushier plants such as peonies, balloon flower, and globe thistle.
Spread a little lime or wood ashes around delphiniums and peonies.
Divide late-summer or autumn-flowering perennials. If necessary, go after phlox and artemisia with a sharp spade or even an ax. If delphiniums need to be divided, remove and replant the new little plants growing around the outside of the clump. Discard the hard old heart.
Trim climbing roses and attach securely to fences or trellises.
Scatter crushed eggshells in a thick ring around roses to deter slugs.
Sow annual poppies and baby’s breath in borders for midsummer bloom by scattering them between the other plants, covering with fine soil, and tamping down gently.
Prune suckers from fruit trees now before they become established.
Melons often benefit from supplemental warming, such as that provided by growing under plastic. Wait until the transplanted seedlings are established, as they cannot take up moisture very well at first and can easily get dehydrated.
Plant aboveground crops in the light of the moon.
Thin beets and lettuce and use the tiny thinnings to fill in spaces in the row or to start additional plantings elsewhere.
For a crop in two years, plant year-old asparagus roots about eight inches deep in trenches lined with rich compost. Fan out the roots and space two feet apart. Cover gently with good soil.
When potato plants come through the soil, hill them up by pulling several inches of soil around their stems with a hoe to encourage deep roots and keep young potatoes from exposure to light.
Mulch between rows and keep the garden weeded to give emerging seedlings a fair chance.
Get that herb garden started by putting in plants. If you include mint, plant it in a large plastic tub (the kind drywall joint compound or birdseed comes in) with its bottom removed. This will help keep it from invading the rest of the garden.
An established asparagus bed will be ready to harvest. Patrol daily and select spears of about the same size (which will require the same cooking time). If you had trouble locating those first spears, mark the bed with stakes so that you can find them next year.
Watch for signs of drought in plants transplanted from containers. Apply water (not much, but often) close to each plant’s stem, where it will percolate down to the root ball. The larger the plant, the longer the recovery period, and the more diligently you need to water. Poke a pointed metal rod into the soil above the root ball. If the rod doesn’t penetrate easily, the soil is too dry. If it moves around and feels squishy, the soil is too wet.
Moles generally come calling this month. They’re searching for mates and also grubs in your lawn. To get rid of the grubs, apply milky spore disease (Bacillus popilliae or Bacillis lentimorbus), a dust you can buy at your local garden center. Or try a new product called Mole-Med, which has castor oil as its active ingredient. Moles don’t like the taste of this any more than you do.
Prune late-flowering shrubs, evergreens, and hedges.
Don’t be in a rush to plant tomato, eggplant, pepper, and other heat-loving seedlings if you live where late-May frosts are common. Old-timers will surely wait until after Memorial Day.
Don’t cut the leaves off spent spring-flowering bulbs. Dying and yellowing foliage may look unsightly, but leave it in place (and don’t tie it up) to help the bulbs ripen for next year’s show.
If you have crocuses growing in your lawn, don’t mow until their leaves have died down.
Don’t force clematis to climb a lamppost or fan trellis. Instead, give it a chance to climb trees, scramble over shrubs, or romp over the ground.