Our wet spring set the stage for plant problems

For gardeners, the spring showers have been too much of a good thing: June's drenching downpours are drowning out hopes for a problem-free garden the rest of the summer.

"We've been on a roller coaster — some of it has been good, some of it has been tough to deal with," said Don Swenson, vice president of Bachman's production department.

You know how to deal with the good stuff. Stroll through the garden with a sense of satisfaction. Invite your friends over and show it off.

Dealing with the tough stuff — plant problems and diseases — well, that's what this column is all about.

Yellow leaves on tomatoes, cucumbers and other vegetables and annuals can be a sign that heavy rains are leaching nutrients out of the soil. Once the soil in your garden starts to dry a bit, Swenson recommends using a liquid or granular fertilizer to revive plants.

Which is better? Shirley Mah Kooyman recommends a dose of both.

"It's like a person," said Kooyman, a native plants specialist for Natural Shore Technology in Maple Plain. "If you're very sick, you want to have a quick squirt of medicine, an injection to become healthier, rather than just trying to get better by eating fruits and vegetables," she said. "Likewise for a plant."

And don't forget your container plants: They need extra food to compensate for all the extra water we've had in the form of rain.

Perennials that are planted too close together may suffer from powdery mildew, according to Kooyman.

"I'm guilty of that," she said. "You buy a 3- or 4-inch pot, and just plunk it in there, wherever there's a space."

Garden phlox and monarda (also known as bee balm) are particularly susceptible to the white fungal growth. By the time you see the mildew, it's too late to effectively treat it. You can either ignore it or pull out badly diseased plants and replace them with disease-resistant varieties.

For the first time in her eight years at the University of Minnesota Extension office, educator Michelle Grabowski said she's seeing blossom blight (also known as fire blight) on crabapple trees.

"We are really watching to see what happens with this," Grabowski said. "Varieties of crabapples vary on how susceptible they are, but the infection can move from the flowers into the stems, then move from larger branches into the trunks and even the tree's roots — which is lethal for the tree," she said.

Unfortunately, it's not wise to prune out those infected branches until next winter. Grabowski said the bacteria can stick to your pruners, spreading the infection.

Repeated rainstorms, particularly when it's warm, help leaf spot diseases like apple scab thrive. Apple scab first appears as brown spots on foliage, said Grabowski, and causes leaves to turn yellow and drop.

Grabowski said the extension office also has been fielding questions about another leaf spot disease, called cercospora, that infects beets and swiss chard. Its fuzzy gray spores can be splashed or blown to other leaves and multiply rapidly.

There are some ways to avoid rainy day troubles.

Trim mature clumps of perennials to give them better air circulation.

And consider raised beds or straw-bale gardens. Done right, they allow for better drainage and give plants a chance to dry out between rainstorms.

Swenson also suggests rotating garden veggies every year, particularly your tomato plants. If you grow them in the same spot every year, they're more likely to develop diseases.

Finally, make sure you adjust your automatic irrigation system so it's not adding to your problems.

"I take a walk around the neighborhood and to me it's kind of laughable. People still have their sprinklers set to go on every day to irrigate their lawns and this is after 5 or 6 inches of rain," Swenson said.