May is a frantic month in northern hemisphere gardens. Warm climates change rapidly to hot climates. Colder gardens suddenly appear out of nowhere and demand attention. You may not need a list of what to do in the garden in May, because it is staring you in the face every time you walk through your garden. But here are some reminders of what you can do. Don’t panic. The season is just beginning.
Everyone
- Treat yourself to at least 1 great new plant before the best selection is gone
- Water regularly, if it doesn’t rain
- Water newly planted plants even if rain is predicted
Flowers
- Deadhead spring blooming bulbs, but let the foliage grow until it yellows
- Deadhead and begin replacing pansies and primroses as the blossoms fade
- Give everything a good feeding, to get things growing
- Divide crowded perennials and share
- Make sure tall perennials are staked
Vegetable
- Keep the perennial vegetables and berries weeded
- Move rosemary plants outdoors, if they don’t live there year round
Houseplants
- Repot houseplants in new soil
Trees & Shrubs
- Check out the azaleas in bloom for future purchases.
- Plant or transplant trees and shrubs before the heat of summer.
Landscape
- Start digging that pond you’ve been talking about.
- Clean bird feeders
- Turn the compost
Pests
- Keep a watch out for asparagus beetles, aphids, cabbage worms, cutworms, scale, slugs & snails and any signs of fungal diseases (leaf spot, mildew, rust...)
- Rip out invasives while the soil and damp, before they spread even further
Northern Gardens
Vegetables
- Keep harvesting cool season crops like asparagus, peas, and spring lettuce
- If you’re not picking asparagus, get some planted for next year
- Seed cool season vegetables and root crops after mid-month (beets, beans, cabbage, carrots, chard, lettuce, onions, potatoes, radishes, turnips...)
- Set out transplants of cole crops after hardening off
- Start warm season melons and squash indoors, to transplant after Memorial Day, when the squash borer has moved on
- Keep seeding lettuce. Start seeding squash, cucs and beans
- Hold the heat lovers like tomatoes and peppers until the end of the month
Flowers
- Finish seeding annuals
- Resist the temptation to put out heat lovers until the end of the month, when night time temps remain above 50 degrees F.
- Deadhead and begin replacing pansies and primroses as the blossoms fade
- Summer bulbs can be planted
- Plant new roses. Prune one-time blooming roses as they faded and feed.
- Give fall bloomers like asters and mums, a first pinching
Trees & Shrubs
- Plant or transplant trees and shrubs before the heat of summer.
- Prune forsythia, viburnums and other spring blooming shrubs, before they set next year’s buds.
- Cut older branches back to ground level to encourage new flowering branches.
- Prune Clematis montana hybrids after blooming to control size and shape.
Southern Gardens
Vegetables
- Direct seed warm season vegetables (melons, beans, okra, squash, southern peas...) for a mid-summer harvest
- Keep cool season crops harvested, so they’ll keep producing as long as possible
- Get heat loving vegetables established (tomatoes, hot peppers, okra, sweet potatoes...)
Flowers
- Replace cool season annuals with heat lovers (marigold, cosmos, sunflower, tithonia, Nicotiana, verbena, zinnia...)
- Feed blooming roses
- Mark bulb plantings that will need division
Trees & Shrubs
- Finish planting new citrus trees and berry bushes for a late harvest
- Prune flowering trees and shrubs as they finish blooming
- Clean up any drooping or ragged fronds on palm trees
Pests
- Keep a sharp eye out for fungal problems during the rainy season
Southern Hemisphere
- Make sure everything stays well watered
- Clean up spent plants and check for over wintering pests and eggs
- Keep planting trees and shrubs including conifers and fruit trees and plants
- Get spring bulbs planted
- Work the soil for winter planting. Check pH and add organic matter
- Consider planting a cover crop
- Bring the houseplants back into the house
- Start reviewing this year’s successes and failures. Keep notes.
