On a foggy afternoon a couple weeks ago, I yanked out bunches of calendulas from my perennial beds. Oh, the plants were blooming just fine — yellow, bronze and orange. But the neighboring roses and lilies were not doing so well.
Calendulas, have a cast iron reputation of surviving just about anything you throw at them. But they also possess an impolite habit of shouldering their way around the garden and crowding out plants. My roses and lilies were left with little breathing room and were suffering from what I call “athlete’s foot” for plants: Gray mold.
The roses and lilies just stood there, buds but no flowers. What was going on? My first clue: They were covered by a gray powder. In the greenhouse, a few potted marigolds suffered the same fate, giant pom-pom flower heads nodding over as if praying. Ah, but the marigolds in the path of the oscillating fan were healthy, while the ones tucked away in a corner developed gray mold. I was on to something…
Athlete’s foot is a common fungus infection that develops between the toes. The fungus grows best in moist, damp, dark places with poor ventilation. (Go barefoot, and you rarely have a problem). Gray mold, is also a fungus (Botrytis cinerea) that thrives in moist, damp places. It causes store-bought strawberries to spoil and raspberries to mold on cloudy days. It attacks hoophouse-grown zucchinis, causes “damping off” of seedlings, and grows happily on bread.
Like I said, the disease is favored by cool, most conditions and little or no wind. A film of moisture is necessary for spores to germinate and infect plants. That’s why cool, damp, poorly ventilated greenhouses and hoophouses are ideal for gray mold, especially when the vents are closed at night or on overcast days to prevent heat loss.
Years ago, I remember talking with a Juneau gardener frustrated with her plants that “melted in the rain.” “I look out my kitchen window and just want to cry when I see my lettuce and flowers keel over with rain and later, mold.
In Kodiak, this summer’s cool weather and rain provided perfect conditions for gray mold. “Gray mold can kill flower parts, leaves, buds, shoots, seedlings, and fruits,” says University of Illinois Extension horticulture educator, James Schuster.
Botrytis cinerea is one of the first fungi described (1729). It is found almost everywhere, from greenhouses to grocery stores. Though it can spread rapidly, Botrytis is a weak pathogen, meaning it usually does not infect healthy, undamaged plants.
How to prevent and stop mold
Gray mold exists everywhere — in the air, on surfaces — just waiting for the right conditions to “bloom.”
That sounds scary, but the good news is that gray mold is easy to control.
So whether you’re starting seedlings, transplanting cuttings, watering a hanging basket or taking care of someone else’s houseplants, the following tips will help prevent a mold infestation:
• Follow good sanitation practices. This is one of the best ways to reduce this disease. Collect and discard faded flower blossoms and fallen petals. In the vegetable garden, remove infected plants immediately after harvest. Plant tissues that are stressed, aging (faded flowers) or not actively growing are great hosts for gray mold to find a footing. (See, there’s that athlete’s foot connection again.)
• Provide good air circulation and don’t crowd plants. It’s easy to plant seedlings too close together early in the season, forgetting that they’ll eventually fill the space.
• Avoid watering late in the day and at other times than do not promote fast leaf drying. Keeping foliage dry is extremely important to control this disease, so avoid overhead watering and overwatering.
• Clean the greenhouse (and the hoophouse as best you can) at the end of the season. Gray mold can over-winter in the soil, in decaying plant debris, and on infected dead plant material.
“Mold has a way of creeping in around the corners of windows in the greenhouse and so I usually wash them with Clorox water or ammonia water,” says Sandee. “I do a major job at season’s end.
• When raising seedlings, use a fan to keep the air moving.
• Sterilize plant containers with a mild bleach solution before re-using them.
“The most effective way of fighting mold is to do your best to prevent it in the first place by providing good ventilation and air movement,” says Sandee. “My fan runs 24 hours a day. Our rainy, cool weather makes it challenging, but I usually have very few issues with molds.”
Turn nasturtium buds into capers
Pickled nasturtium pods (seeds) can be used like capers. In fact, Joy of Cooking calls the pickled pods “Poor Man’s Capers.” Real capers are pickled buds from the caper bush, a shrub that thrives in the Mediterranean region. Capers are a gourmet condiment, and pickled nasturtium seedpods are an impressive substitute.
To make Poor Man’s Capers, start with a brine of salt and water. Add six tablespoons pickling salt to a quart of water. Bring it to a boil, then let it cool to room temperature. Place your green nasturtium pods in a bowl, cover them with brine and set a plate on top to keep them submerged in the liquid.
Let the pods soak for three days at room temperature, then drain them and transfer to sterilized jars. Cover them with white vinegar, add a bay leaf, a clove of smashed garlic and refrigerate. They’re ready to eat in a week and they’ll keep indefinitely.
• Start a compost pile.
• Harvest your crops, and take any extras to the food bank, the shelter or share them with friends and neighbors.
• Divide and transplant perennials.
• Replant in the hoophouse as beds become available.
• Plant spring flowering bulbs like tulips and daffodils.
• Feed your lawn one last time, preferably with an organic fertilizer to help build the soil and improve drainage during the winter rains.
• Prop up tall perennials against fall winds.