May

•    Mulch new beds and cultivate and top off mulch on beds that were mulched in previous years.
•    Immediately after blooming, prune spring-flowering trees and shrubs such as deutzia, rhododendron, azalea, mock orange, pieris, lilac, viburnum, weigela, beautybush, fringe tree and quince.
•    Direct-seed sunflowers and other warm-weather annuals. The lawn also can be seeded still if herbicides or weed preventers weren’t used.
•    Plant tender bulbs such as cannas, callas, dahlias, caladium, gladioli and tuberous begonias.
•    After danger of frost (usually around Mother’s Day), plant annual flowers and warm-weather vegetables such as tomatoes, peppers, melons, cucumbers, sweet potatoes, eggplant, pumpkins, corn and beans. Keep a repellent handy for the rabbits… they love these tender young transplants.
•    Cut spring-bulb foliage after it yellows, never before. Also don’t tie or braid foliage. It’s OK to remove spent flower stalks as soon as the blooms are done.
•    Plant new trees, shrubs and perennials and transplant/divide existing ones.
•    Plant containers, window boxes and hanging baskets. Consider digging up divisions of perennials with good-looking foliage to dress up your containers. Examples: coralbells, hosta, foamybells, painted ferns, lamium and variegated brunnera.
•    Late in month, prune back one-half of the new growth of pines, spruce and fir to encourage bushiness (if desired). If you’re trying to control size of these, remove most of this new growth late May through June.
•    Harvest rhubarb, lettuce, radishes, spinach and other spring-planted crops.
•    Remove any fallen leaves or other rotting organic matter from ponds.
•    Lift and divide any overgrown aquatic plants, begin feeding plants and fish, and add new water-garden plants (temperature permitting) and fish.
•    Keep garden watered – especially newly planted plants – if rain isn’t sufficient.
•    Pull weeds in beds, spot-spray for weeds in lawn or use a weed-‘n-feed product if lawn weeds are everywhere.
•    Continue regular spraying program for fruit trees and roses.
  

  Different stages of the spotted lanternfly.

•   Watch for newly hatched spotted-lanternfly nymphs, which are crawling little spotted black-and-white bugs this time of year. If numbers are high, consider installing DIY “circle traps” on trees to capture them without using insecticides. Instructions are on Penn State Extension’s spotted lanternfly pages.
•    Scout for pest problems and treat as needed. Watch for bagworms on evergreens; tent caterpillars on fruit trees; leafminers on holly and birch; gypsy moths on a variety of trees; woolly adelgids on hemlocks; borer adults on rhododendrons and dogwoods; lacebugs on azaleas and pieris; scale on euonymus, and spider mites on spruce.
•    Gradually get houseplants used to the outside once all danger of frost is past. Most appreciate a “summer vacation” outside, and many make good centerpieces in shady flower pots.
•    Late in month, trim back mums, tall asters, sedum, boltonia and other late-season bloomers that tend to flop by about one-half.
•    Watch for tiny, sticky, black “dots” on siding from artillery fungus growing in mulch. Switch to pine bark, cedar or cypress mulch if it’s a problem.