Taking Care Of Your Outside Plants During Excessive Heat in Indiana

Indiana summers can bring stretches of extreme heat that test even the hardiest gardens. When daytime temperatures climb above 90 degrees Fahrenheit and stay there for days, your outdoor plants need extra attention to survive and stay healthy. By adjusting watering habits, providing shade, and making smart choices about fertilization and pruning, you can help your landscape weather the heat wave. This guide covers practical steps grounded in research from university extensions and Indiana gardening experts.

Indiana summers can bring stretches of extreme heat that test even the hardiest gardens. When daytime temperatures climb above 90 degrees Fahrenheit and stay there for days, your outdoor plants need extra attention to survive and stay healthy. By adjusting watering habits, providing shade, and making smart choices about fertilization and pruning, you can help your landscape weather the heat wave. This guide covers practical steps grounded in research from university extensions and Indiana gardening experts.

Understanding How Excessive Heat Affects Your Plants

High temperatures directly impact plant growth. According to Iowa State University Extension, photosynthesis rates in most plants slow down once temperatures exceed 86 degrees Fahrenheit. When the mercury reaches the 90s or 100s, the process can stop entirely. Plants may wilt, drop leaves, or go dormant to conserve energy. Knowing this helps you recognize that your plants are under stress and need careful management during a heat wave.

In addition to reduced photosynthesis, plants lose water faster through their leaves and soil. The combination of intense sun, hot air, and drying winds can dehydrate a garden in hours. Taking proactive steps to conserve moisture and reduce heat exposure is essential.

Watering Your Plants Properly During a Heat Wave

Water in the Morning

Watering early in the day reduces evaporation and gives plants a chance to hydrate before the heat of the afternoon. Iowa State University Extension recommends morning watering as a key practice during extreme heat. This approach also helps keep foliage dry overnight, which can reduce the risk of fungal diseases.

Check Soil Moisture Daily

During a heat wave, check soil moisture every day. Water when the soil feels dry at a finger's depth. Do not rely on a fixed schedule because conditions change rapidly. Container plants and hanging baskets may need water twice a day during hot, windy weather, as noted by Iowa State University Extension.

Use Drip Irrigation or Soaker Hoses

Overhead sprinklers waste water through evaporation and can wet foliage needlessly. Both Iowa State University Extension and the University of Minnesota Extension advise using drip irrigation or soaker hoses to deliver water directly to the root zone. This method minimizes water loss and keeps leaves dry.

Water at the Base of Plants

Hoosier Gardener and Iowa State University Extension both recommend watering at the base of plants rather than overhead. Directing water to the roots ensures it reaches where it is needed most and reduces evaporation from leaf surfaces.

How Much Water Does a Garden Need?

The University of Minnesota Extension provides specific volumes for gardens. An average vegetable garden needs about 1 inch of water per week, which translates to roughly 62 gallons for a 10-by-10-foot area. During extreme heat, defined as daytime temperatures above 90 degrees Fahrenheit and nighttime temperatures above 70 degrees, water daily or every other day. For that same 10-by-10-foot garden, give 8 to 9 gallons per day. The table below summarizes these recommendations.

Condition Watering Amount Frequency

Typical week 1 inch per week (≈62 gallons for 10x10 ft) Weekly

Extreme heat (daytime >90°F, nighttime >70°F) 8–9 gallons per day for 10x10 ft Daily or every other day

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Protecting Plants from Heat Stress

Apply Organic Mulch

Mulch is one of the most effective tools for keeping roots cool and reducing soil evaporation. Iowa State University Extension recommends applying organic materials such as wood chips or compost around plants. A 2- to 3-inch layer can significantly lower soil temperature and slow moisture loss.

Provide Shade

During a heat wave, direct sun can overwhelm even sun-loving plants. Use shade cloth with 30 to 50 percent density to filter sunlight. For container plants, simply move pots to a shady spot on the patio or under a tree. This temporary relocation can prevent leaf scorch and reduce water demand.

Deadhead Spent Flowers

Plants waste energy producing seeds when under stress. Removing faded flowers redirects resources back to root and leaf health. Iowa State University Extension suggests deadheading during extreme heat to help plants conserve energy.

Hold Off on Fertilizing and Transplanting

Fertilizer promotes new growth, which requires extra water and nutrients that stressed plants cannot support. Iowa State University Extension advises against fertilizing during a heat wave. Similarly, do not transplant or propagate plants until the hot weather passes, as disturbed roots are less able to absorb water.

Delay Pruning

The University of Minnesota Extension recommends waiting to prune until after a heat wave ends and when no rain is forecast. Pruning creates open wounds that can become entry points for disease, especially when plants are already stressed by heat and dry conditions.

Remove Weeds

Weeds compete with your garden plants for water. Pulling them during hot weather reduces this competition and helps your desirable plants get every drop they need. The University of Minnesota Extension highlights this simple step as part of heat-stress management.

Choosing Heat-Tolerant Plants for Indiana Gardens

If you are planning new plantings or replacing heat-damaged specimens, selecting species that naturally tolerate high temperatures can make summer care easier. Fine Touch Services, an Indiana landscaping company, provides these recommendations for heat-tolerant plants that perform well in the state’s climate.

Heat-Tolerant Perennials

Coneflower

Black-eyed Susan

Daylilies

Russian sage

Heat-Tolerant Annuals

Marigolds

Zinnias

Vinca (periwinkle)

Celosia

Hardy Shrubs and Groundcovers

Boxwood

Spirea

Creeping juniper

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Caring for Houseplants That Spend the Summer Outdoors

Many Indiana gardeners move houseplants outside for the warmer months, but summer sun can be intense. Purdue University Extension warns that outdoor houseplants should not receive more than a half-day of morning sun. Afternoon sun can burn leaves. Also, most houseplants are sensitive to temperatures below 55 degrees Fahrenheit, so bring them indoors on cool nights. Check your plants daily and move them to a shaded location if they show signs of scorching.

Lawn Care During Extreme Heat

Cool-season lawns, like Kentucky bluegrass, are common in Indiana. During a drought or extended heat wave, these grasses can naturally go dormant and turn brown. Iowa State University Extension notes that a cool-season lawn can survive dormancy for four to six weeks without significant damage. Avoid heavy foot traffic on dormant turf and do not fertilize. Water only enough to keep the crown alive if needed, but deep, infrequent watering is better than frequent light sprinkling.

Frequently Asked Questions

Should I water my plants every day during a heat wave?

It depends on the plant and soil. Check soil moisture at a finger's depth. In-ground plants may need water every other day if mulched. Container plants and hanging baskets often need water twice daily during hot, windy conditions. Water in the morning and again in late afternoon if needed.

Can I use fertilizer to help my plants recover from heat stress?

No. Fertilizing during extreme heat encourages new growth that the plant cannot support, adding stress. Iowa State University Extension advises stopping all fertilization until the heat wave passes. Focus on watering, mulching, and shading instead.

Will my lawn die if I stop watering it during a heat wave?

Kentucky bluegrass and other cool-season lawns can survive drought dormancy for four to six weeks without significant damage. The grass will turn brown but usually greens up when rain returns. Avoid fertilizing or heavy traffic on dormant turf to protect the crowns.

Is it safe to prune trees and shrubs during a heat wave?

It is best to wait until after the heat wave passes and when no rain is forecast. Pruning creates wounds that can let in disease, and stressed plants have less energy to heal. The University of Minnesota Extension recommends delaying all pruning during extreme heat.

Taking care of your outside plants during excessive heat in Indiana requires a shift in your regular gardening routine. By watering wisely, applying mulch, providing shade, and avoiding stress-inducing tasks like fertilizing and transplanting, you can help your garden survive even the hottest days. After the heat wave passes, assess any damage and replace plants that did not recover with heat-tolerant varieties that will thrive in future summers.

Have questions about your landscaping? Let our experts at Kelly Landscaping know what type of landscaping needs you have in mind and our team can provide a custom quote on your project!