Timely Tips

What to Do in June 2025
Weekly Gardening Timely Tips from
Cornell Cooperative Extension of Westchester County

June 15-21

Perennials: Continue to pinch back mums and other fall blooming perennials until the Fourth of July so they stay bushy and in bloom. Monitor newly planted perennials for water and heat stress. Most perennials thrive with 1-inch of water including rain, but water according to the needs of specific plants if they prefer wetter or drier conditions. Newly planted sun-loving plants that wilt slightly during the day may be protected with shade cloth or lath, placed above but not touching, until well-established.

Flowers: For late-blooming flowers in the border, plant cosmos, marigold, nasturtium, and zinnia seeds before early July. Containers of all types benefit from regular fertilizer to replace nutrients that are leached out as they are watered. Follow label directions.

Fruits and Vegetables: Plant warm-season vegetables like cucumber, eggplant, pepper, okra, squash and tomatoes, especially those that are slower to mature. Faster-maturing varieties (that can be ready in under 10 weeks) can be planted through mid-July. Squash vine borers may be finished laying eggs soon, and fast-maturing varieties of summer squash planted at this time may escape injury.

Trees and Shrubs: Finish shaping evergreen shrubs and hedges by early July. Continue to look on all woody plants and shrubs for the three D’s: dead, damaged or diseased branches and remove them. If indicated by a soil test, fertilize roses after the first blooms have peaked.

Lawns: Grass clippings act as a natural fertilizer for the lawn; if they don’t form clumps, leave them on the grass and save money, time, and hassle of disposal. Grass roots normally begin to degrade as growth slows in the heat. Watering frequency can be transitioned from a single application of 1-inch per week including rainfall to ½ inch, applied twice weekly. Cool season grasses will become dormant in the summer, and may brown in hot weather but recover in full when weather cools, even without a change in water levels.

Houseplants: Summer begins this week.As it gets hotter, remember to continually monitor the soil moisture of houseplants vacationing outdoors. More water than normal may be needed.

Last updated June 14, 2025