Care of Flood-Damaged Lawns and Turf

Written by Dr. Tony Koski, Extension Turf Specialist
Department of Horticulture and Landscape Architecture
http://csuturf.colostate.edu       http://csuhort.blogspot.com

Lawns that are covered by flood waters, even temporarily, may be subject to various types of damage. In general, most turf species will tolerate a few days of flooding without any negative effects. However, turf that remains flooded for more than a few days (especially when it is hot) can rapidly decline due to lack of oxygen and light. Substantial turf loss can be expected after 4 days of continued submersion. Other factors associated with flooding of turf include: soil coverage, water contaminated with petroleum or pesticides, high water temperature and algae scum. The most significant long-term effect of flooding is the deposit of sediment (“muck”), primarily silt and clay, over turf surfaces. This can lead to serious soil layering problems and even death of the existing grass.

Short-Term Care of Flooded Turf
Once flood waters have receded, pick up any debris, such as wood, glass, stones, nails and other metal objects deposited on lawn areas. This debris could pose a safety hazard to mower operators and damage power mowers or other equipment later used to maintain the lawn, as well as to people and pets who may use the lawn for recreation. Remove leaves or any other material that may smother grass.

Soil (“muck”) deposited on a lawn can sometimes be removed before drying by a combination of scooping/shoveling and washing with a jet of water using a hose-end sprayer.  However, removal of soil may be impractical or impossible due to the size of the lawn area, the depth of the soil, the weight of the wet soil, and ability to move it to another location.

Soil deposits on golf greens and other sand-based turf systems (soccer, football or baseball fields) should be removed as quickly and thoroughly as possible to reduce the potential for silt and clay to move into the sand root zone, clogging the pores and reducing infiltration and permeability. The use of shovels, sweepers and water to move/remove soil deposits will reduce the potential for damage. However, these affected turf systems will likely require aggressive core cultivation and topdressing to restore and maintain acceptable infiltration and aeration.

After the Turf has Dried
It is often not possible or practical to remove deposited soil from flooded turf while it is still wet. The drying process may take two or three weeks, perhaps longer, depending on weather, soil, and drainage characteristics of the underlying soil and turf. Remediation at this point is largely dependent upon the depth of deposited soil.

Lawn repair with less than 1-2 inches of soil
Lawns submerged less than 4 days and covered with an inch or less of soil have a good chance to recover.  Assessment of potential lawn damage and recovery may not be possible until those areas have dried. Checking for new shoots emerging from the soil or the emergence of new shoots from surviving plants is a good way to make an early assessment of damage. Usually, once regrowth has begun, it will continue, although it may take several weeks before the lawn has completely filled in.

Core cultivation/aerification is one of the most important and beneficial operations conducted where soil deposits are less than an inch. When the lawn has begun to grow (green leaves begin to appear), go over the lawn 3-4 times with a core type aerifier. This will help improve overall soil structure, improve soil oxygen levels, help break up soil layering problems caused by the deposited soil and encourage recovery during the fall. The lawn should also be fertilized (using any lawn fertilizer, following label instructions for applying the correct rate) at this time (September-October).

Overseeding can also be done at the time of aerification. The aerification holes provide perfect conditions for the germination of grass seed. Lawn areas that are thin (or the entire lawn can be overseeded at this time) can be overseeded with Kentucky bluegrass or a Kentucky bluegrass/perennial ryegrass mix (tall fescue lawns should be overseeded with tall fescue seed), using a seeding rate of 5-6 pounds of seed per 1000 square feet. Rake the lawn lightly after seeding to work seed into the aeration holes. Irrigate the lawn to maintain moist, but NOT saturated, soil conditions.

Lawn repair with greater than 2 inches of soil
Lawns covered with more than 2 inches of soil may be heavily damaged, with only a slight chance of recovery. Degree of recovery will vary with grass species and depth of soil. The greater the depth of soil, the slower the recovery and the less likely the lawn will recover. If the lawn area is completely buried with many (3 or more) inches of soil, then the best strategy may be to accept that the majority of the lawn has already been severely damaged or killed and it will be necessary to reestablish a “new” lawn.

Reestablishment of a “new” lawn over a flood-damaged lawn
To reduce the future potential for soil layering to cause drainage and rooting problems for the new lawn, there are two ways of dealing with the deposited soil. One is to remove as much of the soil as possible, down to the original lawn surface. Understanding that this may be difficult or impractical, the deposited soil may be left on the lawn and rototilled into the lawn as deeply and thoroughly as possible. This, in essence, will create a “new” lawn root zone that is a mix of the deposited soil and the underlying lawn and its soil. The goal is to eliminate, as much as possible, the formation of layers in the “new” lawn root zone by thoroughly mixing the original lawn’s soil, the layer of the original, dead lawn, and the flood-deposited soil.

After leveling and firming the “new” lawn soil, it can be sodded or seeded as any new lawn would be established. Cool-season grasses can be seeded anytime between Aug. 20 and Sept. 30 (buffalograss should be seeded in April/May). Sod can also be used to provide an instant lawn. Do not sod over existing dead or buried vegetation. The old dead layer of lawn grass must be thoroughly tilled into the soil before laying new sod.

Written 18 September 2013

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Sowing success a matter of temperature

In an annual ritual of spring, gardeners emerge from their houses in mid-March, blinking in the thin sunlight as they peer around the landscape, assessing what needs pruning, cleaning, or mending.  All it takes to get our sap rising is for the month to turn to March, and we shrug off our winter lethargy in favor of planting the garden.

 That harbinger of spring acts like a jolt of electricity on our minds, sending a surge of energy urging us to get our hands in the soil and sow seeds.  But if you’re too quick to cave in to eagerness, you might find that your good intentions are not appreciated by the seeds you lovingly pop into the ground.  They’re not impressed by the calendar; they could care less about leprechaun and daylight savings.

 What the seeds want is warmth.  To ensure seeds sprout instead of sulk, gardeners need to plan on two things: frost date and soil temperatures.  Average date of last frost is what most rely upon to plan their plantings; it’s calculated from 30 to 40 years of data.  In Boulder the probability of frost is 50-50 on May 3, in Loveland May 4, and Longmont May 5. 

 Because it’s still possible to get frost after these dates, many gardeners prefer to use the 10-percent probability of frost date as their benchmark, which in Boulder is May 13, Loveland May 16, and Longmont May 17.  You still need to plan for protection from the odd cold snap, but the likelihood of frost is much less when waiting until mid-month.

 Yet there is a second temperature factor that Colorado gardeners shouldn’t ignore: soil.  Chilly soils will limit germination of seeds, and if the ground is both wet and cold, seeds will rot instead of sprouting. 

 Early spring vegetables vary in required soil temperatures.  Spinach and lettuce are the most tolerant, needing soil to be 35-degrees to germinate and 45-degrees or warmer to grow well.  Peas, chard, onions, mache, and parsley can grow in soils at 40-degrees, but do best in soils of 50-degrees or warmer.  Soil temperatures of 60 degrees or warmer are perfect for fava beans, beets, carrots, and leeks, while scallions, Asian greens, kale and kohlrabi like is slightly warmer, at 65-degrees.

  Can these plants germinate in slightly cooler soils?  Yes, but for them to grow rapidly and thrive – key to sweet flavor and tenderness – gardeners should pay close attention to bringing soil temperatures up.

 To do this, plastic mulches or water-filled walls are helpful.  If you’re choosing to go with warming by plastic, clear plastic works better than black at warming soil, bringing the temperature up 10 to 15 degrees in a few days. Make sure you weight down all edges of the plastic to keep it from blowing in the wind, and lay it out so that it touches the soil a week ahead of planting to give your seeds a warm start. 

 Punch holes into the plastic to sow seed if you plan on leaving the plastic in place over the season.  If you are removing the plastic once temperatures are stable, laying the sheets down in strips that can be folded back for planting space is a good way to leave the plastic between rows for a few weeks.  If using water-filled walls, place them out one week before planting to help warm the soil.

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Let it rot

Image via Wikipedia

If your Day of the Dead has turned into a month-long marathon of cleanup, you’re ripe for one of the best ways to recycle your plants into amendment for your soil.  Through the miracle of rot, decaying plants are converted to organic matter that holds water and nutrients for roots to take up. 

Grab a rake and pull up those plants; November is the month to celebrate composting.  Here are few quick and easy tips for getting started:

Pick a sunny, out of the way area at least four-feet by four-feet wide.  If your Home Owner’s Association objects to something decomposing in your yard, use a composting bin to keep things tidy.  Choose one that is well ventilated and allows easy access to the compost for turning.

Gather up green and brown plant material, with twice as much brown as green.  Fresh, green plant parts provide nitrogen to the pile; dry brown material supplies carbon.  Microorganisms need both to turn your garden waste into soil gold.

Avoid resinous wood such as junipers, pine, or spruce; resin keeps the plants from decomposing, increasing the time needed for composting.  Some deciduous tree leaves also take longer, so gardeners wanting a quick batch of compost should avoid oak or cottonwood in their piles. 

 Weeds with seeds and diseased plants should be disposed of in another way; most backyard compost piles don’t get hot enough to kill the seeds or disease.  If you want to compost weeds, clip the seed heads off before tossing the plant on the pile.

Kitchen scraps are good additions to the compost, but not meat, bones, grease, eggs and dairy products that attract animals and insects.  Dog, cat, and human manures should never be added to compost.

For faster composting, chop large material into small chunks before mixing them into the pile.  Leave tree leaves whole so they don’t compact down and smother the pile. 

Layer brown and green material into a pile, adding water with each layer until the pile feels damp, like a sponge.  If the pile is soggy to soaking, add more material in until it dries a little.

There’s no need for soil or compost starter to be added to the pile; microorganisms that break down materials are on the surface of most plant material.  Compost should heat up within a week and be very warm to the touch.

Once it begins to cool, turn it from the outside in and sprinkle with more water to recharge the pile.  Keep turning until it no longer heats up, looks like crumbled humus and has an earthy smell.  Help your compost stay moist in winter by placing a burlap blanket or other breathable material over it.  If your compost cools in the frigid months, don’t worry, once the temperatures warm up in spring your compost, turn your pile, add a little water and the pile will heat up again.

This post was previously published in the Longmont Ledger.

Related Articles

• How to Build A Compost Pile (backyardgardeningtips.com)

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Fast tool for taking your soil’s temp

Ok, I’ll admit it:  I rush the season.  When the weather warms and eagerness overcomes my better sense, I push seedlings and seeds into the soil, tucking them in at the first hint of spring. 

 Because of this I wait as days turn to weeks, wondering if the seeds rotted in the soil.  I wait with impatience as seedlings sit and sulk, unimpressed by their new home.  They’re not dead; I check – those seeds just lay in the ground doing nothing as I put up trellises and string, ready sun shades and mulch.  Clearly one of us is slacking.

Turns out it’s the soil.  If your ground isn’t warm and cozy, the plants won’t thrive, and the jump start I gave the season will fizzle  until that soil heats up.  

Fortunately for us there’s a nifty website you can go to, to check the soil temperatures in your area.  Check out greencastonline.com, a site run by a major company who likes to make sure its seed succeeds.  I’m not endorsing anything here – I just like their soil temp site.   It’s under agronomic crops, should you decide you’d like to click over to weather, then back again. 

Boy, this is fast – currently our soil is 48F, good for planting kale, lettuce, pak choi, parsnips, peas, and spinach.  But days to maturity come into play too, so think ahead to conditions that will be in play once the plant starts producing.  Peas may fry and lettuce bolt in our balmy 90F summer.  But a few more degrees and I can plant the chard or leeks.

Beans typically need soils to be warmer than 60F, ideally 68 – 70F; all of the truly tender crops – tomatoes, eggplants, peppers, cucumbers, squash, pumpkins, corn and melons need the soil to be 70F.  Otherwise they sit there, brooding over the fate that left them in the hands of a rude, thoughtless gardener who plops their bottoms into chilly soil.  Fedco has a great chart for crops and the soil temps they need for planting.

With these two tools you can click on your area to get information on your soil, precipitation, weather, etc.  And this year I intend to use them, so that when I pop my plants in, they’ll leap from the ground and I can get down to the business of gardening, not waiting.

 **Yes, you can warm the soil with plastic, walls o water or cold frames.  Take your soil temp after five days to see how far your temps have increased.

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Which manure do you prefer?

Fellow blogger Susan of Digging In sent along a question from a “mysterious reader” on dung, which gives me the opportunity to muse on the merits of manures:

 

Good soil is critical to successful growing, and gardeners often have entrenched feelings about the best type of material to plow under when preparing for planting.

 

Naturally, manures float to the top of any discussion on amendments.  In spring, when gardeners ask which dung to use, I find myself waxing poetic on manure age, crumble-ability, and animal source as if it were a fine wine. 

 

But answering the question “Which doo will do?” is not easily done (although the obsessed gardener will keep track of manure’s success and failures from year to year). 

 

Horse is always an option, but can be high in weed seed.  I’m no veterinarian, but I’ve been told that a horse will pass what it’s eaten through it’s system every 45 minutes, leaving no time for weed seeds to be, um, processed.  If the horse is on good pasture – one without many weeds – or is fed with certified hay, the problem of seeds is eliminated and gardeners can happily shovel it all over their garden. 

 

In some cases cattle manure could be high in salts, particularly if it came from animals confined to feedlots.  If you need enough to buy by the truckload, ask for an analysis of nutrients from the landscape supply company, including salts.  But note:  many places don’t spend time analyzing manure and asking for a detailed analysis of their poop may get you thrown off the property. 

 

Options expand if the amount you need is small enough:  sheep, llama, rabbit, even designer types such as “Zoo Doo”.  Rabbits produce a great manure – high in nitrogen but won’t harm or ‘burn’ plants with salt.  However, their poo pellets should be separated from wood bedding chips before tilling into the garden (wood chips tie up nitrogen while decomposing, keeping it from plants). 

 

When planning to amend your soil, any herbivore’s doo will do, as long as it is aged before applying it to the garden.  All animals carry eColi in their waste that can be splashed up onto plants during rain or irrigation, so use manure aged six months or longer. 

 

As for the relative benefits or drawbacks of which dung is best, well, that would be decided by personal choice, quantity desired, ready access, and a way to collect it that is borderline rational. 

 

A friend of mine tells me she and her garden buddy get their manure from horses, taking totes over to the stables to collect it.  This gives me visions of festively colored designer totes, held hopefully up to the business end of the horse, those gardeners pleading in their best Oliver Twist voices “please, horse, may I have more?”

 

Another buddy tells of asking her daughter to bring up a suitcase of bat guano on her flight from Phoenix for spring break.  Imagine the ruckus this would kick up at the security station should she need to have her bag searched.  The daughter politely declined, then immediately contacted the rest of the family to discuss having their mother committed.

 

Yet another gardener called to ask me the best way to transport the moose droppings she planned to collect on an RV trip through Alaska, concerned over keeping it fresh.  After gently explaining that the bags would build up methane gas and customs might take issue with an RV of potentially explosive poop, she decided to buy local.

 

Rookies. 

 

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