BY LINDA SCHREIBER
Never mind the 70-degree days Iowans experienced in early April, May signals true spring has arrived with a burst of flowering trees and fragrant shrubs. Gardeners can take advantage of longer days to get yard and garden tasks done to enjoy the landscape and garden in the coming months.
May is the time to get serious about gardening.
When the daffodils and tulips are done blooming you can remove the spent blooms but leave the foliage. Allowing the stems to wither attached to the bulbs sends energy into growing new bulbs as the leaves die off.
Add plant support for emerging peonies, delphiniums and other tall, floppy plants before the plants reach maximum growth. The growing plants will hide the supports and plants won’t be damaged adding supports after they reach their full height or during Iowa’s storms.
Watering is important for newly-seeded lawn areas, new flowers, trees, shrubs, containers and hanging baskets. If Mother Nature doesn’t provide a good shower be prepared to water. Established plantings and lawns need watering every 7 to 10 days.
What to Plant
- Warm temperatures in early May tempt gardeners to get planting. But check weather forecasts first because warm-season plants like petunias, begonias, coleus, and inpatients can be damaged by freezing temperatures and you may need to cover your plants if temperatures drop. Cool-season flowers and vegetables such as snapdragons, alyssum, broccoli and cauliflower are cold-hardy. They can be planted in mid-to-late April.
- Plant shrub roses after Mother’s Day in an area with good topsoil amended with peat moss or compost.
- By early to mid-May after danger of last frost has passed and when the soil is warm, the rest of the garden can be planted, and transplants (tomatoes, cabbages, broccoli) can be added to the garden after “hardening off” the plants. (See the April Thymes for information about this process.) Plant tomatoes in a different spot every other year to reduce fungus disease problems.
- May is an excellent time to plant a shade tree or flowering tree.

delphiniums, peonies, and
other tall plants.
Weekly Tips
Week 1 – If you didn’t aerate in April, now is the time to get that done. Aeration insures water and air are readily available to the grass plants’ roots. It’s also time to mow the lawn if you haven’t already done so. Mow your lawn any time the grass is 1½ times the normal height. The recommended mowing height is 3½ to 4 inches. That would mean you wouldn’t want your grass to get taller/longer than 5¼ inches in height. A taller lawn helps
eliminate weeds and disease and promotes deeper roots. Grass clippings are good fertilizer for the lawn. Frequent mowing eliminates the need to bag or rake.
Week 2 – Fertilize flowers and roses with a complete fertilizer that is low in nitrogen. After the last frost, add annuals to fill in gaps along garden borders for color throughout the summer and fall.
Week 3 – Fill containers with potting soil and create attractive arrangements using tall plants for vertical lines (thriller); larger, brightly colored flowers for focal points (filler); and a variety of complementary flower and foliage colors like attractive vining plants like sweet potato ivy or creeping jenny cascading over the edge of containers (spiller) creates a beautiful focal point.
Week 4 – 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 lilac flowers can be removed but it isn’t essential.
Plant something beautiful!
Resources:
- https://hortnews.extension.iastate.edu/spring-garden-tasks
- https://extension.umd.edu/resource/mowing-or-grasscycling-lawns
- https://www.thespruce.com/mulch-grassclippings-back-into-lawn-2152861
- https://simplysmartgardening.com/what-to-plant-in-may/
- https://www.gardendesign.com/roses/care.html
- https://extension.illinois.edu/news-releases/tips-starting-your-spring-garden-strong
- https://www.gardenersworld.com/what-to-do-now-may/