Great Gardening by Sally Cunningham: Trouble in paradise - The Buffalo News

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Great Gardening by Sally Cunningham: Trouble in paradise

Having expounded about the best gardening season ever (unless you wanted to grow a tomato), I now acknowledge some troubles for even the best of Buffalo flower gardeners. Heavy rains, patches of fog and high humidity, the ubiquitous clay soil that never drains – all conspired to open the door to some ugliness in Garden Paradise.

Soggy baskets, rotting roots

During the last 15 years, gardeners have become increasingly sophisticated consumers, as the industry produced higher-performance designer annuals. As a gardening culture, we generally choose and care for hanging baskets and container plants increasingly well. Most gardeners buy quality plants, use moisture-retentive potting mix and place them correctly. Garden center consumers buy fuchsias and begonias and shade-appropriate plants and know to protect them from the scorching afternoon sun; they place mandevillas and petunias in the bright sunlight they need. Gardeners can usually keep up with the watering – plants have a way of showing you they are dying of thirst – and use the hose when the potting mix feels dry or the basket’s weight feels light.

Then comes a rainy period, and the routines go haywire. Gardeners are grateful they don’t have to water – it’s free! – and forget that too much water is as deadly as too little. Begonias, fuchsias, plectranthus, succulents, petunias – none of them tolerate soggy roots for very long. And rare is the homeowner who moves the container plants or baskets under a table or covers them with a tarp or umbrella after consecutive rainy days. That is what we should have done after the third or fourth consecutive soaking this past week. If you did not, you may own a rotting begonia. Worse, if the plants were in decorative, non-draining planters or window boxes their glorious summer may be over.

To do: If you have overwatered container plants and the stems pull out from the base, it’s too late. In a garden center, the professional would check the root systems to see if they are still viable. You might be able to pull out the plant, cut off any slimy, rotten roots, and put it in fresh potting mix. In a mixed container, pull out the failing plant and stick in a new one, along with fresh potting soil. For the rest of the season, pay attention during extended rainy periods and see that plants have a chance to dry out between human or natural watering.

Many container plants will come through a wet season, however. Some annuals like lots of water and can tolerate standing in water for awhile: cannas, monkey flower (Mimulus alatus, caladiums, elephant ears (Alocasia), calla lilies, papyrus (‘King tut’ series) and several others that are recommended for water gardens. Other plants, in containers with good drainage and the right potting mix, will be fine. And in some parts of the region the rainfalls were just generous and frequent enough for thoroughly satisfying container plants.

Powdery mildew and other fungi

Here is the short version of the lesson called “the disease triangle,” learned by every student of horticulture: A fungus must have the right host to live on, the right weather conditions for a certain length of time and a way of spreading. If your Bee balm (Monarda) is susceptible to powdery mildew, but it is located in a breezy location with no extended period of humidity, it won’t develop powdery mildew. That’s not the case this summer for many Bee balms, as we did have certain humid periods at just the right time. I have seen or been asked to identify several cases of powdery mildew on lilacs, phlox, squash plants and many perennials. Similarly, some roses are developing the fungus disease called Black Spot. I also see evidence of extensive future Tar Spot on Norway maples, another fungal disease.

To do: Wash powdery mildew off plant leaves with a hard hose spray. Thin the plants to increase air circulation. Consider a benign fungicide such as Pharm Solutions and always read and follow product labels. Mostly don’t worry about it: Most of these diseases disfigure, but do not kill, the plants.

Plants beaten down

Thrilled as I have been to see the height of my Rudbeckia ‘Herbstonne’ and my vigorous patch of Veronicastrum (Culver’s root), I was dismayed to see them throwing themselves across their middle-sized neighboring perennials. Worse, I had previously staked them at the 4-foot level but it wasn’t enough to counter the force of the downpours. In other people’s gardens I also saw Goose-necked loosestrife beaten down – the “geese” faces looking up as if from their beds – and many fat hydrangea blossoms bent to the ground.

To do: Most plants will stand up again, unless their stems were bent, cutting off the circulatory system. Do what you can to lift tall, leaning plants off their neighbors. I purchased some 5-foot bamboo trellises and planted them on the downwind side of ‘Herbstonne.’ I used my collection of half-circle plant supports to get a few other plants off the ground. We should all use the moment to make notes, such as mine: Move the variegated Joe-Pye out from under ‘Herbstonne’; use peony rings early around the big-leaf hydrangea.

Too small, not flowering

A few plants really took a hit last winter. If they didn’t die, they are coming back so slowly they are barely worth having this year. Four Buddleias (Butterfly bushes) and a Vitex (Summer Lilac, not a true lilac) died around my property. Two Hardy Hibiscus (Hibiscus moscheutos) finally grew shoots but they are still very short. Even professional landscapers showed me ancient, vigorous roses that died back to the ground last winter. Some plants are marginal, barely surviving Zone 5 winter conditions.

The most common lament I hear is the hydrangea disappointment: “The leaves are great; the plant doesn’t flower.” The winter and cold periods in spring killed off the buds developing on old stems. Heavy mulching over winter might have saved those earlier flowers. Many will still flower, however late.

In spite of all that, the sun is shining on marvelous plants in my garden and I hope in yours. It is still the best garden season ever.

Sally Cunningham is a garden writer, lecturer and consultant.

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