Catherine W. Idzerda" />

Horticultural havoc left in many gardens

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Catherine W. Idzerda
Monday, July 14, 2008
— The grass at Traxler Park smells worse than a wet dog.

Perennials and shrubs are covered with a disconcerting gray-brown film.

Only the trees look healthy, as though having their trunks under water for two weeks didn't really matter.

But that's not the case.

After the flood debris is cleared and the Federal Emergency Management Agency has gone on to the next disaster, homeowners and parks officials will have to tackle the horticultural havoc in their yards.

UW Extension experts talk about what can be saved—and what's beyond hope.


It's hard to hold your breath for six weeks.

And that's what trees have been doing.

Roots need oxygen, and standing water makes it difficult or impossible for them to get it.

Laura Jull, associate professor of horticulture and Extension specialist for woody ornamentals, received a flood—pun intended—of calls about the issue.

She immediately put together what Extension types call "a publication." It's basically a fact sheet covering everything a homeowner and parks employee would need to know about the topic.

Here are the highlights:

-- The effects of flooding depend on a variety of factors including species of tree, type of soil, duration of flooding and time of year.

-- Most plants can take a few days of flooding—but more than that can cause severe injury and death.

-- Tree species susceptible to damage from flooding or wet soils include Norway and sugar maples; Norway and Colorado spruce; white, northern red and English oaks; lilacs; yews, and lindens.

-- Trees species that can tolerate some flooding include box elder; red, silver and Freeman maples; swamp white, bur, pin and swamp bur oaks.

-- Signs of plants under "excessive water stress" include yellowing or browning of leaves, leaf curling and pointing downward, leaf wilting, reduced new leaf size, early fall color, defoliation and branch die back.

What can you do to help?

-- If floodwater has left excess soil around the base of the trees, remove it. More than 3 inches of excess soil will restrict oxygen to the roots, Jull said.

If, on the other hand, floodwater has exposed roots, cover them with soil to prevent drying and additional injury. Again, too much soil can restrict oxygen, so take care.

-- Finally, remember that fertilizing trees or shrubs won't cure root damage.

Both Jull and other specialists said damage might not appear immediately.

Cliff Englert, Janesville parks supervisor, said the very large eastern cottonwoods and other "bottom land" trees in Traxler Park have the best chance of weathering the flood.

"We won't be able to see the results until later this year," Englert said. "Sometimes it can take as much as two or three years to see the damage."


Turf grass doesn't like an extended swim, either.

Again, a variety of factors determine how well the grass will do.

"It depends on the type of grass, the air temperature, the amount of sunlight," said John Stier, associate professor of horticulture and turf grass specialist at UW-Madison.

Kentucky bluegrass, for example, can tolerate being under water for about 10 days.

"Other grasses will be fine for several days—unless the water heats up to 90 degrees," Stier said. "You'll know as soon as the water recedes."

If it's brown, your grass is dead.

Wait until the water has completely receded and your lawn has dried before venturing out on to the yard.

Unfortunately, weeds and weed seeds are less affected by the lack of oxygen.

July and early August are not the time to reseed your lawn.

"You want 60- to 75-degree days and cool nights," Stier said.

Reseed too early and the chances are it will be too hot for the seedlings to survive. Or, the grass will be stricken by pythium, an extremely common blight that causes the grass to wither to a gray-brown and die.

When you do get around to reseeding, Stier recommends renting a slit seeder.

"There's going to be a lot of organic matter on the ground, but there's no need to till or remove it," Stier said.

A slit seeder inserts the seeds into the ground. Tilling, on the other hand, can disturb the seedbed, generating competition from weeds.

If you do till, don't do it deeply.

Until you can put seed down, not much can be done with your lawn, except for raking away the debris. If you want to reseed by broadcast seeding, you can use the time to gently till and rake the soil in preparation.

"Match the grass seed you pick to the situation and the management levels," Stier said.

A fine fescue lawn is inexpensive and is relatively low maintenance.

But it doesn't grow as fast, and it doesn't take traffic very well.

If you have lots of kids running around in the yard, something such as Kentucky bluegrass might be a better choice.

Vegetable gardens

If your garden was flooded, you'll probably want to carefully consider what produce to eat.

"The most conservative answer—and the one that eliminates any and all risks—is to discard produce that was touched by floodwater," UW Extension food science specialist Barb Ingham said in a news release. "In general, produce that was touched—even splashed—by floodwaters, presents a potential risk."

It's especially true of any vegetables that can't be cooked.

Floodwaters contain sewage runoff and other contaminants that can cause serious illness.

But here's some good news: It's not too late to plant.

Spinach, beets, cabbage, carrots, cauliflower, kale, lettuce, radish and even some bush beans still can go into the ground, explained Mike Maddox, UW Extension and Rotary Gardens horticulture educator.

Here's what you need to remember: The first frost date around Janesville ranges from the mid-September to the mid-October. You never know what kind of fall we'll have.

Given that, Maddox recommends:

-- Planting short-season beans. Beans love the warm weather. Check seed packages for the number of days to harvest. Some bush beans need only 55 days. Beans cannot handle frost.

-- Growing lettuce in pots. Lettuce doesn't like the heat. By growing the plants in pots, you can move them in and out of shaded area as needed and into the sun as the days grow cooler.

-- Radishes, beets, carrots and spinach all have seeds that prefer cooler weather. Use an old window screen to provide seedlings with the shade they need and keep them watered. The crops can handle a light frost.


Those with damage from any storms since June 5 who have not filed an application for disaster assistance can do so by calling 1-800-621-3362. Those with hearing or speech impairments should call 1-800-462-7585.

The lines are open from 6 a.m. to 11 p.m. daily, or residents can register online at


Damage from storms last week might be covered under the federal disaster declaration issued on June 14, emergency officials announced over the weekend.

President Bush issued the declaration for storms and flooding starting on June 5.

"The incident period remains open," said Dolph Diemont, who is coordinating the federal side of disaster response.

The declaration covers eligible damage caused by the June 5 storms and anything that comes after that in affected counties until the incident period closes, he explained.

People who suffered storm damage since June 5 should register, Diemont said.

"If they’ve already registered, and their houses have been inspected, they should call the FEMA Helpline to report new damage," he said.

And Wisconsin homeowners in disaster-declared counties might be eligible for aid to help repair flood-damaged wells and septic systems, state and federal officials said.

FEMA grants can help pay to pump septic tanks, perform required repairs or replace the system as needed. Damaged private wells that are the sole source of water for the home also may be repaired or decontaminated.

Home-repair grants are designed to restore the home to a safe, secure and functional condition. To qualify for this disaster assistance, the applicant-owned home must be a primary residence.

Grants are not intended to restore a home to pre-disaster condition and may not be used for cosmetic repairs or repairs covered by insurance, officials said.

The declaration covers 30 counties including Rock, Walworth, Jefferson and Green.

Last updated: 9:49 pm Thursday, December 13, 2012

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