By Kristine Adel
Patrick County Master Gardeners
This summer’s heat has been unrelenting, and if you’re like me, you may have even stood outside watching a water-laden cloud unload for a few minutes on your neighbors across the way – while not a single drop fell onto your garden.
Or even if it did reach your garden, it didn’t drop enough water to make a difference. The sun is evaporating far more water than one cloudburst can replenish.
The effects of heat are devastating on all of our plants especially our berries. We want those berries big, sweet, colorful, and juicy. Instead, the plants are baking in the sun, slowing fruit production, or maybe stopping their growing processes entirely.
Signs of Heat Stress
You may have noticed curling leaves, wilt, yellowing, and/or some leaf drop on your caneberries or strawberries. Their root systems are typically less than four inches deep where the soil dries out fast. Soil in container plantings and raised beds is especially vulnerable to drying out.
Blueberries also have shallow root systems. They may not be showing wilt and leaf drop right away. Instead, the fruit may have stopped developing and begun to shrivel.
Even grape vines with their deep roots are likely to be affected with fewer and smaller fruits.
Cascading Damage – Insects, Disease, and Fungus
Without relief, plants will begin to drop flowers, new buds, and developing fruit. Any fruit that does reach maturity will likely be smaller, less flavorful, and/or deformed. Caneberries may be stunted and discolored as heat stress brings out both White Drupelet Disorder and Red Drupelet Reversion.
Eventually the plants could shut down entirely.
Even if it never comes to that, prolonged and repeated heat stress will weaken your plants’ resistance to pests and disease setting them up for under performance and failure season after season.
A healthy plant that might withstand a few aphids might be overrun when heat stressed – which is bad enough in itself, but even worse knowing that aphids and white flies transmit 76% of all plant viruses.
Fruit flies may become an issue including the invasive Spotted Wing Drosophila (Drosophila Suzukii) which, unlike other fruit flies that infest rotting fruit, will lay eggs into soft skinned healthy fruits, ruining the entire crop.
We might imagine in weather so hot and dry that, at least, we are free from issues with mold and fungus. We might, but sadly, it’s not true. Powdery Mildew thrives in these conditions, inhibiting photosynthesis, flower development, and fruit setting.
What to Do
As always, the earlier you start tackling heat stress, the better. Here are eight suggestions that may help:
1. Water
Drip irrigation is best. Soaker hoses are nice. A bucket of water slowly poured around the entire root system area beneath each plant will work, too.
Try to avoid using a sprinkler if possible. A sprinkler is probably better than no water at all, but keep in mind that cold water on hot foliage in the sun is a shock to plants that are already stressed. The water pressure from a sprinkler can damage tender plants and even erode tree bark, while wet foliage often promotes fungus, especially at night.
Whatever method of watering you use, be sure to saturate the soil at least an inch deep, hopefully more without leaving soil soggy or muddy.
*Keep an eye on your well – water tables may be lower than usual in some areas. If you notice your water pressure diminishing, or you see sediment in your water, stop watering and give your well some time to recover.
2. Mulch
Retain the water in the soil with 3 or 4 inches of organic mulch that will not only prevent up to 50% of evaporation but will also prevent competing weeds and provide a slower release of nutrients as it breaks down. Remember to leave plenty of room for air circulation around stems and canes.
3. Do Not Fertilize
Commercial fertilizers and even some composted organic fertilizers can release nutrients quickly. They may kill your plants outright or encourage the plants to waste energy on new growth that can not be supported in drought conditions.
4. Good Hygiene
If you find evidence of disease, remove it – but do not compost the debris. Always remove plant debris and dropped fruit that would encourage pests and disease.
5. Do Not Prune
Unless you need to remove diseased parts of plants, do not prune. Heat stressed plants don’t need to spend energy healing wounds from pruning. Just try to think of ‘ugly’ as this year’s new ‘beautiful.’ Even dead leaves and branches provide some shade protection from the sun.
6. Evening Shade
Set up some light colored afternoon/evening shade, like a frost cover or an old sheet a few feet away from the plants at a 45° angle to provide some relief. Be sure not to block more than 50% of the light or trap hot air around the plants.
7. Pest Management: Companion Plants and Trap Plants
Consider planting garlic, strong herbs, or marigolds nearby to discourage insect pests. Plant nasturtiums a little ways away from your fruiting plants to draw away (trap) aphids where they can be killed without affecting your fruits.
8. Monitor
Remember, this is a process. There’s no telling how long the drought will last. So stick your fingers in the dirt every day, and water whenever the soil is dry.
Questions? Find us on Facebook or contact us through https://patrickmastergardeners.org/. Don’t forget to tune into WHEO and Patrick County Master Gardeners every 4th, Tuesday from 8:30 am to 9 a.m.
