Lingering Effects from All of That Rain
July 31st, 2018
Besides the mulch and soil washouts and rotting tomatoes from last week’s record-setting rains, we could be looking at some additional subtle and long-term water-related issues in the yard.
Some people got upwards of 10 inches of rain last week.
Yet to be determined is the effect that all of that water had on plant roots — not to mention how much more we’re going to get this week with rain in the forecast every day into the weekend.
If you have good-draining soil or stuck to wet-tolerant plants in sometimes-wet areas, you’re probably fine. In that case, the rain was a plus – better than our usual hot, dry, July oven.
On the other hand, if you have poorly drained areas that were water-logged for more than a day or two, some of your plants may suffer.
When rain doesn’t let up, water fills air spaces in the soil faster than it drains out, depriving the roots of oxygen. Roots need oxygen to live, and without it, they start to die.
Some plants are adapted to deal with soggy conditions better than others. Bald cypress and willow, for example, can be submerged for months and come out fine. Red maple, sweetgum, sycamore, river birch, lobelia, Joe Pye weed, and turtlehead are among those that can slough off weeks of soggy soil.
But others start to suffer within days. Most annual flowers and vegetables aren’t keen on being water-logged for long, and plants from Mediterranean or dry-climate climates absolutely hate it, such as lavender, artemisia, lamb’s ears, and dianthus.
The extent of the damage depends on the plant and how long it sat in water-logged soil.
With limited damage, plants will grow new roots and recover as drier, sunnier conditions return. However, if too many roots rotted, the plant is a goner. This may not be apparent in evergreens and conifers for months down the road – and possibly even next spring if sufficient roots aren’t in place to meet the demands of peak growth.
Ironically, a sign of trouble from too much water is the same as not enough – wilting.
In this case, wilting happens because roots died from suffocating in the oxygen-deprived, soggy soil. Without roots, the plant’s stems and leaves can’t take up water – even if there’s plenty of it in the ground.
So don’t be faked into thinking that wilting plants always mean the plants need a drink. Stick your finger into the ground around the plants to determine whether the soil is wet or not. If it is, don’t add more water.
Early symptoms of plants in excess-water trouble are drooping stems and yellowing leaves. If that’s all the farther it goes, the plants may recover.
Yellowing leaves is often one aftermath of super-rainy spells.
Sometimes trees and shrubs will drop their leaves, which isn’t good but which also isn’t necessarily fatal. Don’t immediately prune or remove a woody plant that drops its leaves in the next couple of weeks. Give it some time to see if more “normal” weather doesn’t result in new leaf buds.
A worse scenario is when whole plants badly wilt and blacken, when branches remain leafless and become brittle when bent, and especially trees that are leaning.
Trees with leaning trunks mean the tree is losing root support, usually from a combination of soggy soil rotting the roots and the weight of water and wind on wet leaves.
Call a tree professional ASAP to evaluate large leaners and stay well away from them since leaning trees could fail at any time.
You might be able to salvage small leaning trees and shrubs by pushing them back upright and staking them. Remove the staking after no more than a year.
Short of setting giant hair-dryers around the yard, there’s not much you can do about sogginess damage.
The real solution is up-front: sticking with wet-tolerant plants in wet areas, improving drainage by working compost into the soil at planting time, or creating raised beds.
You’ll probably do more damage by walking on soggy beds in an attempt to cut drainage channels or by poking holes in the soil. It’s best to stay off soggy ground and let Mother Nature do the draining.
Two other problems with saturated soil:
1.) Lack of oxygen can suffocate the microorganisms in the soil that break down nutrients. Without those little “fertilizer factories,” plants may suffer nutritionally and show it via yellowing or discolored leaves.
This should eventually correct itself, but in the short term, give yellowing plants a boost with a treatment of granular fertilizer, especially products containing nitrogen and iron.
2.) Many disease organisms thrive and spread in wet soil. The worst are fungi that cause root-rotting – a double whammy for roots already struggling from lack of oxygen.
That one’s a hard one to control. Fungicides help in a few cases, while moving early-sufferers to a higher, drier spot also can salvage them.
Watch for moisture-fueled plant diseases, such as leaf spots (left) and powdery mildew (right).
Warm, wet conditions also are ideal for fungal leaf-spot and mildew diseases on a range of perennials and woody plants, especially lilac, black-eyed susan, hydrangea, roses, bee balm, and phlox.
Most plants grow through these kinds of diseases, but for more serious outbreaks (or if you have a low tolerance for plant damage), fungicide treatments might be warranted.
Extension offices can help with diagnosing, or send samples to Penn State’s Disease Clinic, or use the University of Maryland’s online Landscape Problem Solver.
Read George’s article on 8 ways to keep your plants healthy
A few other yard things to consider as you mop up after the rain:
* For tree and shrub roots that were exposed due to soil erosion from moving water, cover the roots ASAP. Bring back the washed-out soil if it’s nearby. Otherwise, you’ll have to buy topsoil.
Ditto for fixing channels carved by fast-flowing water.
Return soil and mulch that’s washed out to its original home, if possible.
* For soil or mulch that washed into piles or up against plants, remove it and ideally return it to its original location. Piled-up soil and mulch can smother plant roots, and even 2 or 3 inches of soil or mulch over a lawn can kill grass underneath within days.
* Don’t be too anxious to cut grass where the soil is still soggy. Better to cut twice later than squish the soil by walking over it or running a mower over it when it’s wet.
* If your vegetable garden just got soggy from too much rain, toss the rotted stuff, and you should be fine.
However, if the garden was flooded by a creek or stream, that’s a different story. That water could be contaminated with bacterial pathogens from flooded septic systems and manure runoff or from chemical pollutants, such as oil, gasoline, and assorted household chemicals that floated out of garages and basements.
The safest bet is to toss anything that’s come into contact with flood waters, especially plants with ridges and nooks that are hard to clean, such as lettuce, kale, basil, broccoli, and cauliflower.
For more on this, the University of Wisconsin Extension has an excellent article called “Safely Using Produce from Flooded Gardens.”
* If water backed up in your flower pots due to inadequate or no drainage, try tipping them as best as you can to pour out excess water. If possible, drill or poke holes in the bottom.
Otherwise, remove the plants ASAP and plant them in a drier spot. Salvage the soil by dumping it and laying it out to dry for a few days. It can then be reused.
Dump any standing water you find in the yard.
* Check for standing water. If any is hanging around yard ornaments, plant dishes, and any other open containers, dump it so mosquitoes don’t breed.
* Assess where your yard ran into drainage issues and fix them. This might include clogged or faulty spouts, temporary “rivers” (fixable by adding buried drainage pipes, swales, or dry stream beds of rock), and washouts where downspouts drain into beds (fixable by adding drainage pipes or a stone bed).
* Think about adding rain gardens to capture runoff instead of letting it run rampant and overtax our storm sewers and creeks.
For more on that, read my past article on rain gardens.