Always knowing the when to plant, prune, and harvest.
All you need is the right checklist.
What To Do In Your Flower Garden This May (Late Spring)
May is a beautiful month in the flower garden.
But it can also be a challenge to know where to start when it comes to gardening chores.
I’ve put together a comprehensive flower gardening checklist with some of the best advice for what to do in your garden this month.
May Flower Gardening Tips
- Begin planting warm-season annuals.
- Bulbs can be moved or divided as the foliage dies.
- Stake tall-growing perennials that will need support, if you haven’t already done so.
- Cage or provide support for peony blossoms when the plants are 10 inches tall.
- Deadhead perennials as blooms fade. This will encourage healthier growth and prevent unwanted self-sowing.
- Divide mums and other late bloomers.
- Divide early spring bloomers when they finish flowering.
- Cut back delphiniums after they bloom to encourage fall bloom.
- Pinch back chrysanthemums and other perennials when six inches high to encourage compact growth and larger blooms. Pinch once a week until the middle of July. This promotes stocky growth.
- Pinch azaleas and rhododendron blossoms as they fade. Double-flowered azaleas need no pinching.
- Mulch around perennials. Be sure to leave 2 to 3 inches around the base of the plant free of mulch to prevent rotting.
- If you didn’t plant summer bulbs last month, plant lilies, freesia, gladiolus, calla lilies, and crocosmias after all danger of frost has passed.
- To extend the blooming period of gladiolus, plant early, middle and late season selections each week until the middle of June. Choose a sunny location and plant the corms four to six inches deep and six to eight inches apart.
- Keep an eye on the soil moisture levels for plants growing in pots and containers. On warm, windy days, hanging baskets will require water every day. Always water the soil thoroughly before fertilizing your containers. Terra cotta pots will dry out faster than plastic.
- Lilac blossoms will last longer indoors if they are cut in the morning. Cut long woody stems when the flowers are only half open. Cut the stem a second time indoors before and make a vertical slit up the woody tissue and putting them in a vase.
- Monitor roses for insects and diseases. Check daily for black spot, especially in wet weather. Do not handle rosebushes if the foliage is wet and infected. Wait until the leaves have dried before removing them and spraying. Watering roses with soaker hoses or drip irrigation will reduce the spread of black spot disease.
- This is a good time to remove unwanted “volunteers” – seedlings of perennials and annuals from last year. Move them to a new location if you have one. If you don’t have room, don’t feel bad about putting them in the compost heap.
- Continue to weed. Thistle and dandelion tend to come on strong this month.
- Try growing annual vines to provide interest in a small, vertical space. They can disguise ugly walls and fences. Try morning glory, nasturtium vine, and scarlet runner bean.
- Deadhead faded flowers.
- Lavenders and other sub-shrubs may still be partially dormant. Pruning too early can kill these plants.
- Prune off any foliage damaged by a late frost.