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Gardening / What happened and why?

This season’s problems and failures



Hostas are a favorite plant for a reason; they are relatively problem-free.

Photos by kc kratt

 

As serious August overtakes joyful July, some gardeners will observe that everything didn’t turn out exactly as planned. Maybe some plants you bought were disappointing. Some flowers stopped flowering and the leaves turned ugly. The lawn didn’t stay thick, green, and weed-free. And the Father’s Day gift tree suddenly dropped its leaves. Was the gardening hoopla of June just a big hoax?

 

Actually, this dark scene probably does not describe most experiences, but when bad things happen, we want to know why. As with most of life’s disappointments, we need context—those horticultural principles that explain so much.

 

• Most plant failures are cultural—meaning weather, site, soil, or care. Those conditions determine health or survival in ninety-five percent of cases. It is rarely about a  “sudden” pest or disease.

 

• Healthy plants can handle most insects or disease attacks. In nature, all plants deal with insects, fungal spores, and other passing annoyances. If plants are healthy, they usually thrive or survive anyway, just as a healthy person survives the same flu that kills a frail person. Poor watering causes most short-term plant deaths. Annuals, container plants, and vegetables typically die from inadequate water (when people water shallowly instead of deeply), but standing in too much water is also a killer. Recently planted trees, shrubs, and perennials die most often from poor watering during their first three years in the soil, while they are trying to grow roots.

 

• Established, large trees take many years to die. When you see an old tree failing, look to its experience during the past five years or more: were the roots cut during construction? Did it suffer a series of droughts or flooding? Were recent winters significantly different, with extreme temperature fluctuations?

 

Knowing these things, you can surmise what might have happened to your tomatoes, lawn, trees, roses, or Rudbeckia. This season, some specific, daunting problems surely prevailed. Earlier this summer, I asked a few experts from different plant specialties what they would expect based on the way the season began. There was consensus: The cold, wet weather in late spring would prove to be the dominant factor for most garden and landscape disappointments—and it would all show up in August.

 

Troubles with turfgrass

John Braddell of Lakeside Sod was confident about what to expect in the turfgrass world after a very difficult start to the season. It was impossible to mow many lawns until weeks past the normal time. The grass looked thick and green but, in reality, the roots remained shallow—they can’t live in muck. Some homeowners reported a swampy smell, indicating anaerobic soil conditions. Some people skipped the late May fertilizing stage. Then, when the summer heat came on, the small roots dried out quickly.

 

Recently seeded or sodded lawns may also have succumbed to any hot, dry weather. Braddell said, “You have to be tenacious about watering a recently seeded lawn. The fragile little root hairs will shrivel and die unless the soil is dampened continuously. That might mean watering in the heat of the day when necessary. If you see cracks between pieces of sod, water it deeply!”

 

Solution: late summer is the perfect time for seeding, sodding, amending the soil with compost, and improving the drainage for future wet spring periods.

 

Woody plant woes

Some trees and shrubs had a fabulous spring, if they were growing in the right place. However species that require excellent drainage may have stood in soggy soil for weeks—perhaps the last straw for them. Some trees that don’t tolerate wet soil for long periods are blue spruces, crabapples, Eastern hemlocks, yews, and white pines.

 

Spring 2019 also provided optimum conditions for some fungal and bacterial diseases. Some of these may sound familiar:

 

Apple scab, especially on ornamental crabapples: this fungal leaf disease appears as mottled greenish-brown spots, and sometimes black velvety fungal growth. Many leaves fall in midsummer, and rough, round spots appear on the fruit. The disease impairs the beauty and weakens the trees over time.

Solutions: Clean up fallen leaves, prune to increase air circulation, and consider early-season fungicide (dormant oil) treatments. Or choose newer scab-resistant cultivars that are now available.

 

Black spot on roses: Fungi live on fallen leaves in winter. In wet spring periods, the spores splash onto new leaves and you see black spots. Eventually leaves yellow and fall off.

Solutions: Choose black-spot-resistant roses. Clean up fallen leaves. Avoid wetting leaves when you water.

 

Spotty leaves that dropped in early summer (Anthracnose): Sometimes, in June, nearly all the leaves drop from sycamores, ash, dogwoods, oaks, maples, walnuts. It happens after cool, wet weather in spring. Leaves first turn blotchy, with brownish spots between veins.

Solutions: Otherwise healthy trees come through, because they have summer months to grow more foliage. A certified arborist might assist highly valuable specimens, but mostly treatment is not practical.

 

Root rots: When soil is compacted or poorly drained, and when a landscape plant is placed in an unsuitable site, roots may develop several types of rot diseases—specific to the species. A variety of symptoms may show above ground in August but by the time you see symptoms, it is often too late.

Solutions: Plant in the right place in non-compacted, well-drained soil; keep plants healthy.

 

What perennials reported

A few perennials have declared a banner year. Others look their worst, with fungal diseases that began in the cold and wet spring. (Some diseases also result from excessively humid summer periods.) These listings are just a sample of some serious culprits and their victims.

 

Disease and symptoms and the plants commonly affected:

 

Anthracnose: dark spots or sunken lesions leading to a severe blight

Bergenia, Dianthus, Epimedium, Heuchera, Hosta, Phlox, Rudbeckia, Sedums

 

Rust: obvious rusty spots that poof or smudge

Asters, Campanula, Hollyhocks, Iris, Mallows

 

Downy mildew: Beginning with oldest leaves, upper leaves first show light patches, then lower leaves develop fuzzy clumps of spores.

Asters, Coreopsis, Impatiens walleriana, Lupines, Potentilla, Rudbeckia, Veronica, Viola. Some weeds are alternate hosts.

 

Powdery mildew: White powder over the plant parts

Asters, Coreopsis, Liatris, Monarda, Phlox, Zinnias, Rudbeckia

 

Observing the veggies

Vegetable gardeners soon learn to expect certain pairings of specific crops with specific problems, and this season will reinforce those expectations.

 

Tomatoes

Blossom-end rot appears in August as darkened, softened bottoms on the fruit. It was caused during the blossoming period, typically in June, when the plant received too much or too little water. The uneven watering prevents uptake of calcium that affects the blossom and causes later defects in the fruit. (Similarly, cold soil or air temperatures during the tomato’s formative weeks cause other defects such as cat-facing or cracking.)

It’s important to get an accurate diagnosis of early blight, late blight, fusarium wilt, verticillium wilt, tomato mosaic virus, or others. That’s because your responses should differ: some diseases remain in the soil, so you should rotate crop locations and use fresh soil mix. Some diseases overwinter in discarded plant debris or “volunteer” plants next year. Look for disease-resistant cultivars (marked with V, F, TMV on the labels).

 

Squash, cucumbers, pumpkins, gourds, some melons

Powdery mildew is observed in August, a powdery film over the plant parts, followed by withered, shriveled leaves. It does not kill plants but reduces production. Usually home growers can harvest enough of the crops even after the leaves are gone. Farmers may use some fungicides. For home gardeners, it’s usually sufficient to space plants well and choose resistant varieties.

 

Salad greens and peas

Peas, lettuce, and spinach require cool spring soil and temperatures. Most people couldn’t plant them early enough this year, so when the heat came on the peas got tough and salad greens bolted and became bitter. Suggestions: when we begin to have cool nights, plant cool-season plants for a fall crop.

 

Before you forget all that happened this season, make some notes. When problems have occurred, a correct diagnosis and good science usually provide recommendations for future prevention. Good plant culture increases success—right site, right planting, and right care. And some problems of 2019 were unavoidable: it was the weather.

 


 

Common problems of any season

 

1) Blossom end rot (tomatoes)

Uneven watering in June can contribute; look for disease-resistant cultivars.

 

2) Powdery mildew on squash

This should not affect production. Space plants well and  choose resistant varieties.

 

3) Lily leaf beetle

Vigilant picking and squashing in the early season is the best treatment so far. Neem oil is somewhat effective.

 

4) Apple scab

Early season dormant oil may help; also, prune to increase air circulation.

 

 

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