Timely Tips

What to Do in May 2026
Weekly Gardening Timely Tips from
Cornell Cooperative Extension of Westchester County

May 24 - 30

Perennials: Continue pinching back mums and similar late-flowering plants to about four inches. Repeated pinching of late flowering perennials until late June or early July promotes business and more flowers. Later pruning may delay flowering. Conversely, consider thinning disease prone perennials. Thin perennials such as old-fashioned phlox by removing up to a third of crowded and thinner stems at ground level. This increases air circulation and can help to reduce powdery mildew while increasing the size of the flowers.

Flowers: Prepare indoor-seeded warm-season flowers by gradually exposing seedlings to the outdoors before planting. Set them outside for up to an hour on the first day and protect them from direct sun and wind. Gradually increase their outdoor exposure every day. At the end of a week or so, when the plants can remain in full sun all day and spend a warm night outdoors, they’ll be ready for transplanting. Spring bulbs can be deadheaded or moved when plant material yellows.

Fruits and Vegetables: Don’t rush the season with warm weather crops like tomatoes and cucumbers. Unless weather is very warm with soil temperatures above 70°F at a depth of 2 inches, planting early may not be helpful. Cold plants don’t put on much growth, if any, and may sustain injury. Warm season vegetables planted later in warm soil can quickly catch up and surpass earlier plantings.

Trees and Shrubs: Finish up pruning azalea, forsythia, rhododendron, viburnum, and other early spring-blooming shrubs before next year's flower buds form. Tie the stems of climbing or rambling roses horizontally, as along a fence. This will encourage plants to produce more flowers than on stems that are tied vertically. Roses are a preferred host for young spotted lanternfly nymphs, so check the plants regularly.

Lawns:Flowering broadleaved native plants and other nectary plants can be maintained with turfgrass as a “bee lawn.” Research shows that 2 to 3-week mowing intervals allow for the greatest diversity of pollinator species while successfully maintaining lawn flowering. Continue to overseed bare and thin spots to get the lawn through summer for aesthetic purposes. Save major renovations until late summer or early fall.

Potted plants: Pinch back plants that look thin to encourage bushiness. Make sure they have adequate light and are growing in an appropriate potting mix with adequate moisture and fertility. Indoor plants can be moved outdoors for the summer when night temperatures are reliably in the 60s°F. Many houseplants need some shade outdoors or favor only direct morning sun.

Last updated May 25, 2026