Keep gardens thriving through the heat

UNIVERSITY OF MINNESOTA EXTENSION - www.extension.umn.edu

A drip hose delivers water to the soil for a deeper soak.

This week’s drastic temperature swing has stressed gardeners and plants alike. Hot, windy days pull moisture from leaves faster than roots can replace it, and even well-watered plants can wilt, curl, or stall out.

Recognizing the signs of heat stress early and responding quickly keeps gardens thriving through the toughest stretches of summer.

Signs of heat stress

• Leaf wilting: The classic droop, even when the soil is moist. 
• Leaf curl:  Tomatoes, peppers, and annuals fold leaves inward to conserve moisture. 
• Scorching or crisping: Brown edges or bleached patches from intense sun and hot wind.
• Flower drop: Tomatoes, peppers, and cucumbers shed blossoms at around 90°F. 
• Stalled growth: Plants pause to conserve energy; fruit set slows.

Time watering wisely

• Early morning watering: 5 to 9 a.m. is ideal for hydration and quick drying. 
• Deep, infrequent watering: Long soakings at the root zone; soaker hoses are better than sprinklers in wind.
• Avoid “sips”: shallow watering leads to weak roots. 
• Check soil, not leaves: Heat alone can cause wilting even when moisture is adequate.
• Evening watering: Safe on hot, windy days; foliage dries quickly.

Protect annuals, perennials and veggies

• Temporary shade: Lawn chairs, old sheets, or 30–40% shade cloth during peak heat.
• Wind breaks: Move containers to sheltered spots; use fencing or trellises to block hot southwest winds.
• Mulch maintenance: A fresh 1–2" top-off keeps soil cool and slows evaporation.
• Container rescue: Shift pots to morning sun/afternoon shade or double-pot to insulate roots.
• Cut-back strategy: Lightly trim crispy annuals to encourage fresh growth once temps moderate.

Annuals and perennials

• Perennials: Mulch and morning watering help; watch shade lovers closely.
• Annuals: Afternoon shade and deep watering revive them.
• Containers: Water daily during heat waves; sometimes twice.

Vegetables

• Tomatoes: Leaf curl is protective; blossom drop is normal.
• Peppers: Mulch heavily; avoid overhead watering. 
• Cucumbers and squash: Scorch easily; water at the soil level.
• Beans: Pole beans handle heat better; keep soil evenly moist.
• Lettuce and greens: Shade immediately; harvest early.

When temperatures soar and plants suffer, remember:

• Water early and deeply.
• Add or refresh mulch.
• Shade vulnerable plants during peak heat.
• Expect blossom drop on tomatoes and peppers.
• Don’t panic! Most plants bounce back once temperatures ease.

Don’t forget yourself! Hydrate often, and, if possible, work in the garden before 10 a.m. or after 4 p.m., when UV rays and excessive heat and humidity are lower.

More resources from Extension

• Gardening in hot weather

• How heat affects the vegetable garden

• Water Wisely