It was a banner year for mildew. It showed itself later than usual and hit harder when it came.
Often, gardeners who know their phlox or bee balm or cosmos is prone to mildew will scout for gray but fail to recognize the disease when it causes leaves to brown and die.
If we were play-by-play garden broadcasters, this growing season’s week by week commentary would have sounded like this:
“No mildew, yet. Janet.” “Right-o, Steven, but it’s early for that.”
“Still no mildew.”
“Plants so clean!”
“Amazing. No mildew.”
Until late July, when:
“Wham! Tons of pale spots – it’s here!”
“Check out that gardener’s moves, cutting out discolored leaves in veg beds.”
“It’s a brawl, Steven! They’ll need machetes to keep up cutting out discolored leaves.”
“Will you look at that, Janet?! Even fothergilla and boxwood are mildewed!”
“Give it up now, team! This win goes to the Gray Tide!”
Mildew fungi are ubiquitous. In the U.S. desert southwest farmers can grow crops that fail elsewhere on account of mildew susceptibility. Yet it’s not an absence of fungi that creates that haven but a lack of humidity. It’s tough growing for fungus where the air is very dry. Our most common mildews can grow and reproduce only when temperatures and humidity are just so.
“Just so” didn’t happen in our area until late July this year or even early in August. However, when it came, this fungus showed its gray face not only on its usual hosts - phlox, bee balm, zinnias, cosmos, squash, lilacs, etc. – but also on the leaves of redbuds, peonies, and many other plants. If you’re wondering this fall why a plant’s leaves are unusually dulled, cupped or coated, make mildew your prime suspect.
In most cases, mildew had already infected leaves by midsummer and was at work, stealing nutrients. It simply did not experience favorable weather and could not enter its reproductive phase – producing its distinctive gray spores – until late summer.
The smart move now is to clean away the gray. Hot compost the infected leaves or at least move them as far from your most mildew-prone plants as possible. Then, next year, recognize mildew in its earlier stages and do more leaf clean-up.
Keeping the pumpkin vine healthy has been a chore made more bearable because we aren’t protecting only that plant. There are our late beans to consider. (Late because their towers were in use for a very long time this year by pea plants that went on and on into August. What worked against mildew seems to have favored peas.)
In addition, consider relocating the worst affected plants to better sites, because stronger plants resist infection. Look into mildew resistance, too. A plant that mildews every year is not pulling its weight. There are mildew resistant varieties of just about everything. Now may be the time to retire some and bring in fresh players.
A native wildflower followed us from our previous, wetter garden. Hoary vervain (Verbena hastata) probably came to our new, drier, shadier home as tagalong seeds.