The July weather statistics are starting to fly from the tip of every meteorologist’s tongue, but you don’t need the numbers to know it’s been an unusual month on top of the sixth-wettest June in meteorological history. Our plants are telling us all about it.
It’s not all bad news, though. Wet weather is good for gardens and gardeners in many ways. Plants that love or require moist conditions had a wonderful start, including astilbes, ferns, Rodgersia, Sanguisorba, shrub dogwoods and willows. Hostas and butterfly bushes are huge. My water garden and bird baths have rarely needed topping off. Lawns are green, and sprinklers have stayed mostly in the garage.
Even the compost piles are having a good year, as is my back. There’s rarely a need to moisten the piles or turn over layers to encourage “cooking.” When I reach a few inches inside the pile, it is nearly always damp and warm.
Unexpected benefits, all these.
On the other hand, I’ve heard many of your laments and seen some sad cases where persistent or hard rainfall incurred damage. Often the rain in June and July was a pounding rain accompanied by thunder, lightning and great gusts of wind. What’s a little coreopsis to do?
• Pounded down, blown over: Simple physical damage happens when hard rain slams plants to the ground. I mentioned the coreopsis because I’ve seen many such fine-stemmed plants practically flattened, and yet they perked up like itsy bitsy spiders when the sun came out. On other plants, more brittle stems, crowns or branches just broke or snapped off. Some plants were smashed not by the rain, but by the neighboring Japanese willow, ornamental grass or Lespedeza that leaned on them.
• Flooded root systems: Some plants have low or no tolerance for standing water and will die if their roots are soaked for just a few days. If you’ve enjoyed a clump of coneflowers for a few years, even though they were planted in clay soil in a poorly drained bed, this might be the year you learn that they require good drainage. Other plant species can tolerate standing in wet soil, but they don’t grow during that period. Roots require air as well as moisture in the soil in order to take up nutrients, so an over-watered plant can wilt, drop leaves and fail to grow the same as a plant in a drought.
• Not enough sunshine: Rain is usually accompanied by cloud cover, and that means the sun wasn’t shining on us much in June and parts of July. Some plants need full sun, others partial sun and all need some light to grow and flower. Many flowers and vegetables needed more sunshine than they received, although some are catching up now. Pollinators need sunshine, too, and some fruits or vegetables were ready for pollinating and no bees showed up.
• Human misunderstanding: Many people have been asking nursery professionals something like this: “My hydrangea (or redbud, apple tree, etc.) planted this spring (or last year) just looks terrible … dropping leaves, brittle leaves, showing fall color, drooping. What can I do?”
Clues show up when we talk about when and how it was planted and watering practices. People tend to believe there has been plenty of rain, and they didn’t water adequately during some very dry periods. Yes, there were long weeks with ample rainfall, but new transplants have small root systems that can dry out very quickly, so the plant owner must ensure that the water gets to those roots the day they go dry. The fact that it rained last week, and it may rain tomorrow, does not help those shriveling root hairs.
Do you remember those extremely hot days with high winds a couple of weeks ago? The hotter the temperature, the faster the soil dries out, and wind accelerates the drying. Wind also quickly wicks away moisture from plant leaves or needles.
We all would like simple explanations and remedies. The truth is that horticulture and biology aren’t so simple, with many variables among plant species, and our weather patterns this season have been extreme and changeable.
It’s not a surprise that many plants, especially recently planted ones, have gone down or may do so, this season.
Not rain, but humidity
Humidity is not the same as wet conditions, but we have had some hot and humid as well as some cool and humid weather conditions. Fungus diseases require specific conditions, including some level of humidity. Most familiar plant diseases are fungal (rather than bacterial or viral), including rusts, mildews and leaf spots on roses and other plants.
• Rust on hollyhocks: I simply expect rust to appear on hollyhocks, from the lowest leaves upward. A breezy location, generous spacing between plants and thorough cleanup of plant debris all may minimize rust development slightly. But if the weather is right, rust will grow. Fungicides, including horticultural oil, may suppress the disease, but if you love hollyhocks, anticipate rust. Put medium-tall plants in front of them so you see just hollyhock flowers and not the rust.
• Powdery mildew: Powdery mildews – powderlike coating – should be expected on some phlox, Monarda, Pulmonaria, lilacs, ninebarks and others. Crowded conditions, poor air flow and humid periods contribute. You can wash or rub it off or treat it with horticultural oils or other fungicides according to the labels. These mildews are usually disfiguring rather than life threatening.
If you have a strong need to control your universe, you won’t be a happy gardener. This season has provided many conditions out of our control, and all we can do is assist the plants we have. Assess the site and your care, and figure out what to do differently for plant survival this year and a better season to come.
Considering the challenges of the season, isn’t it remarkable how many gardens amazed and delighted thousands of visitors in the past weeks?
Sally Cunningham is a garden writer, lecturer and consultant.