Welcome to the busiest month of the gardening year! Planting, sowing, watering, staking, mowing, fertilizing… there’s so much to do, and every time you turn around, there’s another weed!
But if our gardens demand a lot from us this month, they give back more than their share. To me, May is the most beautiful month in the garden. Immersing myself in its life and color is the reward for a to-do list as long as my arm.
Watch the Weather and Remember to Water
May can trick us with a late frost, which can kill or injure emerging foliage and turn some flowers into mush. Frost doesn’t happen every year or everywhere, but to be safe, watch night temperatures like a hawk and be ready to move or cover vulnerable plants.
Tomatoes, peppers, eggplants, and tender annuals such as begonias, impatiens, and coleus should be protected if night temperatures go below 55 degrees. Or play it safe and just don’t put these plants out overnight until after May 31st, when nights are warmer.
We usually receive reliable rainfall this month, but be prepared to water perennials if there’s five or six days of dry weather, because lack of moisture can affect flower formation.
Newly sown seeds and seedlings, container plants, and anything you’ve planted in the last month should be checked every day and watered if necessary.
Sowing and Planting
With the caveat about late frosts in mind, begin sowing seeds and/or planting transplants of vegetables and flowers, among them beets, carrots, lettuce, cosmos, nasturtium, and bachelor’s button. Plant asparagus, fruit trees, and blueberries.
Keep dividing and transplanting perennials, as well as trees and shrubs. Do as much as you can earlier in the month, before June’s warmer weather sets in. Keep them watered.
Plant summer-blooming bulbs: dahlias, caladiums, gladioli, and warm weather annuals such as petunias, marigolds, and geraniums.
Start planting up containers, window boxes, and hanging baskets. Incorporate a slow-release, granular fertilizer into the potting mix when planting.
Lay sod or seed a lawn before the weather gets hot.
In the last two weeks of May, begin hardening off the seedlings you started indoors by putting them outside in a sheltered place each day and bringing them in at night. Leave them out only a few hours at first, and extend the time as the days go on.
Pruning, Feeding, and All the Rest
Prune lilacs! There’s an exclamation point there because they set flower buds for next year soon after bloom, so you only have a few weeks to do it. Also prune other shrubs that have finished flowering, such as forsythia, azalea, rhododendron, and weigela.
Fertilize emerging perennials and roses with a balanced, slow-release granular fertilizer formulated for flowers. Use a light hand; it’s easy to overfertilize. In the short term overfertilizing can give you floppy plants, long term it can throw the nutrient balance of your soil out of whack. An inch or two of compost provides nutrients without the fear of overfertilizing.
Apply a slow-release, high-nitrogen fertilizer to your lawn. Mowing starts in earnest this month. Cut the grass high, at two inches or more, to encourage deep roots and reduce the need for watering.
Deadhead pansies and other cool weather annuals to keep them blooming. Also deadhead spring-blooming bulbs. This keeps them from forming seeds, which reduces a bulb’s vigor.
Stake or trellis summer-blooming plants and vines.
Start watching for insect pests such as rose slugs, aphids, cutworms, slugs, and snails. Curse rabbits, groundhogs, deer, and squirrels. (Honestly, you can put up fences and spray deterrents, but be prepared for frustration. Nature always finds a way.)
Catch annual weeds before they go to seed. Try to weed when the soil is moist, the weeds come out easier that way.
Continue mulching areas you haven’t gotten to; time spent now will save you work in the future. There’s a whole story on which mulch to use and how.
Edging beds with a spade or edger gives them a clean, crisp look plus it helps keep grass and weeds from creeping into flower beds. It’s the quickest way to make the garden look spiffy.
And no matter how busy you are, take a minute to stop and smell the flowers!