Gardening Tips-May

May is an extension of April in terms of caring for your garden.  There’s more pruning, mulching, seeding and plant division.  One thing May does bring which is nobody’s favorite are weeds.  But get on top of those nasty invaders now before they become even harder work in the summer.

When it comes to planting keep in mind the possibilities for a late, damaging frost.  The Farmer’s Almanac is predicting 27-April as our last frost with a 30% chance of one occurring after that date. 

Weed, Transplant, Mulch

  • Pull weeds before applying a fresh new layer of mulch on landscape beds.
  • Water-in all transplants. Planting on a cloudy day will minimize the shock to new plants.
  • Pinch off the first set of flowers on annuals to encourage better rooting and bloom later in the season, particularly during hot weather.
  • Avoid pushing emerging seedlings with fertilizer until they show at least three true leaves
  • Summer bulbs can be planted out now (May 1 or later) including gladiolus, dahlias, caladiums, crocosmia and tuberous begonias.


  • Summer and autumn-flowering perennials can be divided if there is not extensive new leaf development. Consider dividing yarrow, chrysanthemums, hostas, phlox, daisies and daylilies. Keep the new plants well watered for a few weeks.
  • Cut out dead wood on roses and figs, and prune to just above a growing bud pointing away from the center of the plant; adjust ties for climbing roses onto their frames
  • Put peony supports in place before the new growth becomes too high; thread stems through the grid as they grow. On tree-peonies, remove any shoots from below the soil if they are different from the true leaves/stems of the parent plant (they come from original grafting root-stock).
  • Flower and shrubbery beds can still be fertilized. Use a product with slow release fertilizer for extended feeding and to protect water quality.
  • Do not remove or bundle up leaves from spring bulbs.  The bulbs need the leaves to replenish their food stores for next year’s bloom. Wait until they die back naturally. If you want to relocate daffodils, go ahead and dig them, with leaves attached, and replant as you would any other transplant.
  • Spring-flowering perennials should be dead-headed, pinched back or sheared after they have finished flowering.
  • Summer bloomers like butterfly bush, rose of Sharon, and crape myrtle can still be pruned in early May.
  • Do not dead-head biannuals if reseeding for the following year is desired.
Creeping Phlox
Peonies Support

Lawn Care

  • After May 1st it is too late to do any seeding as there is insufficient time for the new grass to get sufficiently established before the higher summer temperatures bear down on us.
  • Mow frequently enough to remove no more than 1/3 of grass blade at a time.
  • Mow cool season grasses 2½ to 3½ inches high.
  • Do not fertilize fescue and bluegrass lawns. Nitrogen not used up by June is an invitation for brown patch fungus disease. (Late summer/early fall is the best time for fertilizing).


  • Plan the vegetable garden on paper. Keep the plan from year to year so you can plan crop rotations.
  • Allow the recommended space between plants, whether you are seeding or transplanting. Good air circulation is important for disease control and plant development.
  • If you are following the Square Foot method of gardening and are unsure of how many plants to put in a square, use the recommended plant spacing on your seed packets as your guide (ignore row spacing). For instance:
  • 1 per square for plants that require 12″  spacing (cabbage, peppers, some tomatoes),  4 per square for 6″ spacing (Swiss chard, leaf lettuce),   9 per square for 4″ spacing (beets, beans, spinach),  16 per square for 3″ spacing (radishes, carrots, scallions)
  • To “harden off” warm season transplants, begin a week or two before planting out, setting seedling trays outside during the day in a protected area and water as needed. Ideally the soil temperature should be above 55 degrees before planting (likely the end of May) otherwise the seedlings will just sit there and take longer for major growth to get started.
  • Tomatoes (non-grafted)– when planting transplants, remove all the foliage except the top leaves and dig a hole deep enough so you can plant right up to the leaves. Cover the stems up to the top leaves with soil. The buried stems will produce roots all along its length. Adding calcitic lime at planting helps prevent blossom-end rot.
  • Tomatoes (grafted)–Make sure to keep the graft line above the soil so that the scion (the half of the plant above the graft) does not take root.
  • No room for a vegetable garden?? That does not necessarily mean you can not grow a few fresh fruits, vegetables and herbs. Tuck some vegetables plants into a sunny flower bed or under-used border. For that sunny flower bed consider ornamental looking Swiss chard, kale, onions, cardoon, basil, fennel and other herbs. Grow cucumbers on a trellis.
  • Consider growing some vegetables in containers. This is often a good option if the only sunny space you have is the deck or patio.


  • Turn over the compost pile. With warmer weather, the microorganisms will kick into high gear.
  • Insects are essential for pollinating many crops. Honeybees and other pollinators are very vulnerable to insecticides. Think twice before using an insecticide and know what you are targeting.
  • Clean and fill hummingbird feeders. The first humming birds arrive in NJ around May 1st.