Strategies for High Heat

July's combination of high temperatures and long days puts plants under maximum stress with minimal hours of cool recovery time. How you manage soil, water, planting, and shade will make a bigger difference now than at any other time in the year.

Give both new and old plants their best shot (and make your labor go farther) by following best practices for hot weather: 

• Plant the right seeds to start with. Choose vegetables and flowers that are meant for the season. For example, spinach is a winter green, while chard is a summer green. Varieties of the same vegetable can vary a lot too. For example, Rattlesnake pole beans continue to bear in hot spells, when popular varieties like Kentucky Wonder and Blue Lake burn out. Commercial lettuce is grown in cool, foggy places. We need different kinds than what you see in the store. Batavian or Summercrisp types are more heat-tolerant.
• Soil should be moist enough to prevent wilting in afternoon heat (though large-leaved plants like squash may droop a bit.) But make sure they have plenty of water during morning and evening, when plants can actively grow, rather than just survive.
  
• Normally you'll want to water in the morning or evening. In very hot, dry, or windy weather, you may need to water the soil around plants to cool the air a bit. However, do not get water on the leaves during intense sunlight. It will act as a lens, and concentrate the sun's heat. I have seen leaves burned crisp by being wet in direct sunlight.
  
• Reduce competition for water. Follow recommended spacing and keep beds weeded. If plants are stressed and you can’t water more, thin them to wider spacing. 
• Keep the soil covered with mulch. In hot weather, use a light-colored mulch like straw. This not only conserves moisture, it also prevents compaction and shelters soil life that creates fertility.
  
• Wind dries plants worse than heat. Provide some shelter.
• Before planting, work in organic matter to hold moisture and release it slowly to plant roots. Compost is ideal. After planting, you can layer compost on top of the soil and under your mulch. 
• Provide shade to reduce temperatures at ground level. Seedlings and new transplants are particularly vulnerable to extreme heat, sunlight, or wind.
• Plant a wide variety of flowers, herbs, vegetables, shrubs, and trees. Plants thrive in an interlocking community, with some shading others. Perennials are deeper-rooted and more resilient than annual vegetables.

The unique thing about gardens is that they’re habitat for both plants and people. Increasing the comfort, beauty, and diversity of the garden makes it better for both.