May Gardening Tips


May brings an explosion of flowers with plums, cherries and flowering crabapples putting on a fabulous show that is quickly followed by fragrant lilacs, brightly colored azaleas and many other beautiful trees and shrubs.  This is the month when gardeners will be taking advantage of the longer days to complete a variety of yard and garden tasks that will pay off with  an attractive home landscape over the coming summer and fall months.  May can be a busy, but try to make time for enjoying the beauty of the spring flowers and the birds and butterflies that follow the warm temperatures north.


Weekly Tips


Week 1    Lawns that are thin, lumpy or have heavy foot traffic will benefit from core aeration.  The cores will quickly break down on top of your lawn and contain microorganisms that help break down thatch.  Aeration insures that water and air are readily available to the grass plant’s  roots.


Week 2    Finish cutting back dead tops of perennial flowers and any dead or broken branches in roses and other shrubs.  Fertilize flowers and roses with a complete fertilizer that is low in nitrogen.


Week 3  Mow your lawn any time the grass is 1 ½ times the normal height,  For example if you mow at a 3” height, don’t let the grass get longer that 4-5”.  You may need to mow twice a week during this time of year.  More frequent mowing eliminates the need to bag or rake up clippings.


Week 4  Fill containers with good  potting soil and create attractive arrangements using tall plants for vertical lines; larger, brightly colored flowers for focal points; and a variety of complementary flower and foliage colors.  Many attractive vining plants such as sweet potato vine will cascade over the edge of the containers and create a softening effect.


Week 5  Now is the time to prune spring flowering shrubs that have finished blooming.  Older branches may be pruned to the ground; longer branches shortened, and any crossing and broken branches removed.  Spent flowers on lilacs may  be removed but it isn’t essential for getting good bloom next year.



Garden Maintenance


  1. Remove spent blooms on tulips, daffodils and other spring flowering bulbs.  The plant will put all of its energy into growing new bulbs. The leaves are needed to form new bulbs so leave them until they die in early summer. 
  2. Install plant supports for peonies, delphiniums and other tall, floppy plants before the plants get too tall.  The growing plants will hide the supports and plants won’t be damaged during a sudden thunderstorm. 
  3. Hummingbirds and orioles return to northern states by mid-May.  Clean and refill feeders to attract these colorful birds to your backyard. 
  4. Watering is very important for newly seeded lawn areas; new flowers, trees, shrubs, containers, and hanging baskets.  Even established planting and lawns may need watering in May if we go 7- 10 days without a good shower. 

 What to Plant


1.     Warm temperatures in early May tempt many gardeners to advance the planting season.   However, petunias, begonias, coleus, impatiens and other warm-season plants will be damaged by freezing temperatures and are not safe to plant until after May 20th.  Cool-season flowers and vegetables such as snapdragons, allysum, broccoli and cauliflower may be planted in early May.


2.     Shrub rose plants make a great Mother’s Day gift and can be planted right after the holiday in an area with good topsoil that has been amended with peat moss or compost.


3.     Plant tomatoes, peppers and  melons after all danger of frost is gone and the soil is warm. This is usually the last week in May.  Plant tomatoes in a different spot each year to reduce fungus disease problems.


4.     May is an excellent time to plant a shade tree or flowering tree in your yard.  Visit the Arboretum and get ideas on the best trees for your yard while you enjoy one of the most beautiful places in the country during the peak, spring bloom season.  Especially interesting is the Pillsbury Shade Tree Exhibit.