Avoid Plant Sunburn and Summer Garden Disasters
How Much is Full Sun? Not as Much as You Might Think. Shady Is a Good Thing.
Reading Time: 9 minutes
Plant sunburn, floods, heat and hailstorms. Planning now protects your garden from disaster later.
When you started your first garden, did anyone tell you that Mother Nature might rake her nasty claws through your chard and hurl your cabbages through chain link? Probably not. Tutorials and advice draw a rosy picture of peppers sitting beneath a gentle, smiling sun, not a rabid heat-monster that shrivels pumpkins and flicks tomato blossoms off before they can set.
No, you usually find that out right when you’re running out with a bucket, attempting to catch hail before it can puncture through leaves. Summer weather is unpredictable and extreme. From plant sunburn, torrid heat, windstorms and flash floods, it can wreak havoc with your vegetables.
What can you do to save your crops?
Heat and Plant Sunburn
By this time, it’s probably too late to choose drought-tolerant plants or amend your soil with organic material so it retains more moisture and helps plants recover from stress. Yeah…that would have been nice right around March. Now your tomatoes are permanently in the ground and probably several feet high. Assuming summer is the best time for gardening, you sit back and wait for ripe, round fruit. But it never comes. And you go outside and check the blossoms to discover that they break off at the joint, falling to the ground, when they should be pollinating and producing groceries.
The hard truth is that most plants do not like the summer heat. Even “warm weather” crops wilt or refuse to set fruit above 95°F.
It’s not too late to mitigate heat and plant sunburn.
First of all, consider the term “full sun.” If you spend enough time in a desert climate, such as where I live, it’s easy to assume that “full sun” means a day of the same sunlight that lets you fry eggs on rooftops. “Full sun” is actually six hours. And it’s usually sunlight within a climate that regularly sees clouds. If you live in high elevations and don’t have regular cloud cover, you may need to avoid plant sunburn by providing shade.
Plant sunburn kills patches on leaves, trunks and fruit, and can be identified by a white area on the most exposed area of the plant. That area will die. If the scald is small enough, the rest of the plant will recover but the scald will not heal. The best way to protect against plant sunburn is to harden plants off before setting them out permanently. Crops grown within a greenhouse have never experienced the full, brutal wrath of pure sunlight. Introduce them gently. Set out for an hour the first day, two hours the second, increasing until they can spend all day outside. If you prune crops such as tomatoes, don’t expose areas that have previously been shaded. Beautiful fruit, sheltered by a wide leaf, turns rough and ugly from plant sunburn.
The second-best way to avoid plant sunburn is with shade. Remember how I said “full sun” was six hours in an area that has clouds? Filtering out harsh sun does wonders for garden health. Expensive tarps promise to reduce UV damage by 60 percent. Commercial shade cloth allows 80 percent of light to shine through. And threadbare white sheets, purchased at garage sales, can provide the same protection for much less money. Even planting your tomatoes where a tree shades them from noon to 3 p.m. helps. Use garden hoops for smaller crops or clip shade cloth to tomato cages.
Mitigate heat down below as well. A light-colored mulch such as straw retains moisture in the soil as well as reflecting the sun in the same way that white clothing is cooler than a dark sweater.
Some states are still recovering from one of the worst droughts in history, settling hard on a large agricultural area. Others live in a constant state of drought.
Before dry weather hits, avoid problems by choosing plants that are hardier, use less water, have tougher foliage, and can go without moisture a little longer before sacrificing quality. Amend soil as well. The sweet soil balance is “loam,” a balanced percentage of sand, silt and clay. If you don’t have loam, add compost, aged manure, and other plant-based material. A high percentage of organic material holds more water. It also feeds more nutrients to plants, allowing them to withstand stress. Poorly nourished vegetables are among the first to succumb to Mother Nature’s wrath.
Mulch is a gardener’s most important tool against long, dry spells. It shields dirt from sun, which may kill microbes, wind which may strip away topsoil, and allows plant roots to stay cool. Mulch also holds moisture in the ground, reducing the amount of watering needed. It regulates moisture so the best fruit can develop. Do not leave soil bare to the elements.
Water wisely during drought, using driplines if possible. Soaker hoses, pointed downward, are another good option. Combine drip irrigation with mulch to keep each drop where it belongs. Water at night or in the morning, when water is least likely to evaporate before it can sink in. Areas that experience powdery mildew benefit from morning watering so moisture does not remain on leaves for long periods of time.
Water, Water Everywhere
Last summer, I experienced stale chips for the first time while visiting coastal California. I live in a climate where corn chips sit for three months in an open bowl and are just as crisp as day one. It also rains so rarely that new gardeners call me in panic, asking, “It’s raining! Do I need to cover my plants?”
Relax. Rain is a good thing. Usually.
Wetter states experience frequent rainfall and have soil ready to handle it. Flash flooding is more of a Western desert thing, and facts about floods prove it can be devastating.
Most plants can handle rainfall as long as it doesn’t contain hail or isn’t driven by hurricane-force winds. Leaves may bow down from the moisture but they rarely receive more than a few rips. It’s the soil that suffers. If dirt is heavy with clay, water doesn’t sink in. It runs off, taking topsoil with it, or sits around roots to drown the plants.
Construct your garden with drainage. Digging trenches between rows allows excess moisture to roll off and collect away from the roots. Dig in a bit of a slope so flooding runs downhill and out of the garden bed. By the time those trenches fill with water, your plants have had more than enough anyway.
If you haven’t thought that far ahead and you watch in panic as water pools beneath your pumpkins, don a raincoat and arm yourself with a shovel or hoe. Scrape trenches into the soil, drawing a path from the pond to the edges of your garden. The same emergency technique can be used in chicken runs or animal stalls to divert water elsewhere.
And speaking of flooding: If you’re experiencing a level of natural disaster, and your garden sits in water washed in from who-knows-where, do not eat the produce. Food pulled from flood waters may be covered in harmful bacteria. Don’t cook them, can them, or even compost them. Disinfect any boots or gloves you used while working in a flooded area.
Foresight can save your garden when the angels hurl ice cubes from the heavens.
Though pea-sized pellets won’t do worse than puncture leaves during a short storm, prolonged exposure strips foliage and breaks branches. The larger hail gets, the more damaging it is. And the time to think about preventing damage isn’t when golf balls fall from the sky.
Protection is simple: cover your plants. It doesn’t have to be fancy. Overhead structures such as trellises or pergolas either block the hail altogether or slow its descent. Ice bounces from the surfaces and rolls to the ground. Previously constructed grow tunnels can stop hail as well as harsh sunlight, though the pellets may puncture thinner fabrics.
Keep a stash of emergency covers in a shed: Old five-gallon buckets, empty planters, or milk jugs with the tops cut off. If the hail isn’t dangerous to you, run out with a hat on. Upturn containers over the plants and let them stay on until the storm is over.
If the hail has damaged your plants, do not remove leaves that are only a little punctured and torn. As with plant sunburn, may be ugly but they can still photosynthesize for the plant. Remove broken stems and branches, sterilizing pruners before and between cuts so disease doesn’t spread to an already-stressed plant.
Ragged greens and herbs can still be used if harvested before bacteria can sit in the leaves’ wounds. Dice greens then boil them into soups. Dehydrate herbs or use them fresh to make a garlic oil recipe.
Back east, hail is often a precursor to a tornado. This changes the rules when you think about protecting plants because objects like pots and buckets can fly around in harsh winds, doing more damage than the wind itself.
A little wind is good. It’s what pollinates corn. But too much can plow through a small homestead and leave swaths of destruction. If your area is prone to high winds, you probably already know it. And if you just moved in, ask local gardeners if you need to worry about dangerous gusts. Whether they’re tornadoes, hurricanes, or seasonal gales, they can shred leaves and blow cornstalks to the ground.
Before the storms can hit, construct windbreaks such as hedges on the outskirts of gardens. Or plant crops beside buildings or walls. Stake tall plants such as tomatoes at least a foot into the ground. Anchor slender fruit trees with guywires or poles. Keep your garden tidy, stashing loose items in sheds, so they don’t become wrecking balls hurled by the wind’s cruel hand.
Watch the weather reports. As the warm air mixes with cold and the gusts build, run outside and harvest all the fruits and vegetables you can. Tomatoes and peppers with just a hint of color will still ripen indoors. Then hold on and hope for the best.
You can’t choose whether tornadoes or hurricanes devastate your crops. And if they do, salvage what you can. Rinse plants and soil with clean water if you live near coastal areas; they may have salt left from seawater that blew in. Dig out the soil to drain any standing water. Compost debris if it has not come in contact with flooding.
Recovering From Disaster
The rain and hail stopped, the wind cleared, and the water drained. Now the sun shines relentlessly once again. Take a deep breath and don your gloves. You have work to do.
Don’t leave debris lying around the garden. Trim away broken stems and branches with sterilized shears. Right now you need to help surviving plants recover, which means avoiding disease from dirty tools. Don’t cut off leaves that are minimally damaged by hail or plant sunburn because the plant needs these to build strength and produce more foliage. Unless you need to wash away salt or contamination, let the soil dry before watering again.
If you survived a natural disaster, your dirt may not have. Erosion can wash away fertile topsoil. Replace both nutrients and lost topsoil with compost and a prepared soil mixture. Depending on the damage and the time of year, you may need to replant. And if it’s already late in the summer, you can still get a fall crop in.
Whenever Mother Nature cackles and rubs her hands together, preparing to play ping-pong with your eggplant, you’re going to fret and worry no matter what. But if you know how to survive weather disasters within your garden, you can minimize damage and often come out with a full harvest.
Have you dealt with disasters like floods, storms, or plant sunburn? Sharing what you learned can help other gardeners.
Originally published in the July/August 2016 issue of Countryside & Small Stock Journal.