Roots and Shoots: Adapting to Summer

parasitic wasp

A parasitic wasp laid eggs inside this tomato hornworm. The cocoons look like grains of rice. (Photo by P. Doan)

Every garden season is different; that’s what makes it interesting. But the impacts of climate change are making things different in new ways, a trend that will be more challenging in the years to come. 

This summer we’ve had dry spells, record rainfall in the first part of July, several heat waves, lower-than-average temperatures, smoky skies, storms with strong wind gusts and heavy rainfall, many high humidity days, and it’s not over yet. Hurricane season runs through November, so we have months ahead with the possibility of more extreme storms. 

Don’t give up! Whether it’s protecting the vegetable garden harvest, fruit trees or trying to preserve the beauty of landscaping, there are techniques and methods that can help stabilize conditions for plants. 

Row covers 

Fabric covers draped over plants or on hoops and secured with ground staples can achieve greenhouse conditions without a greenhouse. Different weights of fabric allow access by 30 to 85 percent of sunlight and water and help control soil temperature and pest damage, though I haven’t seen research about protection from pathogens. 

In spring, heavier fabric helps warm the soil faster for earlier planting when winter just won’t end. Soil temperatures can be raised 2 to 8 degrees, depending on the fabric weight, and that can mean a harvest 1 to 3 weeks earlier. 

If secured well to the ground, a row cover is a barrier to prevent insects from reaching the plants and weed seeds from blowing in. For plants that need pollination, pull back the cover once the female flowers bloom to allow bees in. 

In summer, lighter-weight row covers can stabilize the temperature for plants and screen out harsh sunlight on the hottest days. If the row cover has been in place since the crops were planted, stay on top of weeds to prevent seeding. Insect pressure will be less intense. Since the greenhouse effect holds in moisture and heat, in summer make sure to open the row cover for more air circulation and to keep plants from getting too hot. 

In fall, a row cover will keep the soil warm longer and extend the growing season. While protecting plants from frost (the frost date here is Oct. 15) and freezing temperatures, try growing vegetables that you would plant in early spring, like greens and root vegetables. I’m not promising that tomatoes will make it until January but spinach, carrots and beets might be viable in our warmer winters. 

Insects controlling insects 

Another way that weather patterns affect the growing season is through insect pressure. Aphids have had a fantastic season this year, judging by my garden and the comments of gardeners in online groups that I follow. Large amounts of rain have produced fast growth and abundant foliage this summer and the aphids have followed. Lots of food leads to larger populations. 

Spider mites thrive in hot, dry weather. Wet springs can decrease cutworm populations. No matter what ecosystem lever is pulled, our gardens respond. 

Ladybugs, including New York’s endangered, native 9-spotted variety, are wonderful consumers of aphids. They are attracted to flowers that have pollen and nectar. Try planting cosmos, dill or goldenrod to attract them. Lacewings eat many plant pests and their eggs, including thrips, mites and aphids. They appreciate similar pollen and nectar flowers. 

One of my favorite beneficial insects are parasitic wasps that lay eggs inside caterpillars. The larvae hatch and basically eat the caterpillar until it dies and they are grown. This process is most commonly seen in the garden on tomato hornworms. The key is to let the host caterpillar munch the tomato leaves long enough to allow the baby parasitic wasps to grow to kill more hornworm caterpillars. The sacrifice is worth the benefit. 

Rain, rain go away or not? 

Heavy rainfall can cause root rot in poorly drained soils and evaporate quickly on hot days. This year in a rush to get a bed of tomatoes planted, we mulched with handfuls of a pile of last year’s grass clippings mixed with shredded leaves and it’s been the best mulch I’ve had for water retention and weed suppression. 

When it comes to water, follow some simple techniques. Set up a storage system like a rain barrel or barrels for dry periods. Improve soil to retain and drain. Use mulch to keep soil from drying out. Be wise with watering by measuring the amount of irrigation and avoiding overwatering. Watering systems that focus on plant roots rather than foliage are most effective. 

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