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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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With apologies to Frank Loesser, his song, Baby It’s Cold Outside, has been running through my head with a few changes:

We really can’t sleigh (baby it’s dry outside)

The warmth’s got to go away  (baby it’s dry outside)

This winter we’ve been (hoping that snow’d drop in)

Not very nice (I’ll warm up the hose, it’s stopped up with ice)

Trees aren’t the only thing that need water in a dry winter – and boy, is it dry.  The federal Climate Prediction Center has said most of the Front Range and all of eastern Colorado is in a moderate drought.  We’ve gotten just a whisper of water since July, so monthly watering of your landscape is a must. 

In a previous post, how to water your trees was described, but lawns, too, need a drink.  “Established lawns will benefit from watering, but the critical ones that need moisture are the ones that are new,” says Dr. Tony Koski, Extension Turf Specialist with Colorado State University Extension.  If you put down sod after September 15, you should water it. 

Even if you don’t have a new lawn, watering the grass is important, and if you’ve been plagued by lawn mite problems in the past, water that yard soon, he said.  “This is when mite populations start to rise, especially on warm days when they get a little active and frisky.  They’re frisking around, the population starts to rise, and though mites haven’t started to damage the lawn, their potential to do so increases with their numbers.”  Mites prefer bone-dry grass, so hold them at bay with moisture. 

To water a lawn in winter, warm days with temperatures above 45-degrees is a must.  Fortunately we have plenty to choose from, since we’re in the 50’s and 60’s several days per week.

Drag out your hose with a sprinkler, or set the water to a slow trickle.  “The problem is that everything is frozen, but you don’t want water puddling on the lawn.  And the worst thing is forming a layer of ice on it; that really harms the turf.  So it probably won’t take more than a quarter to half-inch of water before you get standing water and puddles.”

Set your timers to tell you when to move the hose or shut off the water.  Most importantly, disconnect the hose from the house before evening so you don’t run the risk of frozen pipes.

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If your lawn stays thirsty even though you water often, you might have a problem with thatch.  Thatch is a brown, spongy material made of grass stems, living-, and dead grass roots that forms a mat along the surface of the soil.  It resembles peat moss in look and feel. 

Though thatch can be useful in small amounts to help keep the soil cool and the lawn comfortable to walk on, once it gets thicker than a half-inch, it turns into a big problem for lawns.  Plant roots are lazy when it comes to penetrating a resistant soil, and most plant roots will remain in the easy-to-grow area created by thatch, instead of forcing their way into compacted soil. 

Over time, the major part of the grass’ root system gets limited to the thatch layer, which doesn’t hold water or nutrients well.  The result is turf roots drying out and top growth burning back despite excessive irrigation.  Once this happens, the recommended amount of water will not be enough to keep your lawn healthy. 

 Thatch can be a problem on Kentucky bluegrass, bentgrass and fine fescue lawns, but rarely on tall fescue or buffalograss.  To help slow thatch buildup core aerate each year to break it up and encourage roots to grow into the soil profile.  But wait to aerate until fall or put it on your calendar for spring – mid-summer is not a good time to open up a bunch of holes in the soil for the heat to dry out.

Contrary to myth, grass clippings don’t add to thatch problems; use a mulching mower to leave the clippings on the lawn to recycle the nutrients they contain.

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Hosting the family picnic seemed like a good idea months ago, but looking over the struggling lawn, are you wondering what possessed you to say “yes” to this event?  With cousins bringing footballs and aunties croquet mallets, what should be a cause for celebration is now a source of panic. 

If the date is looming while the yard is dying, get it in shape with coaching from an all-pro turf master.  With no room for error before your relatives arrive, here are a few tips from one who knows how to handle the punishment a wild bunch delivers to a lawn. 

“Give it four to six weeks and you can have a pretty good lawn,” says Ross Kurcab, Turf Manager for the Denver Broncos, who keeps Invesco Field at Mile High ready for play.  “It won’t take a lot of traffic but it will get you through the event, after which you can plant for recovery of it.”

Kurcab shared tricks turf managers use to jump start fields for the big show.  His quick fix suggestions aren’t for everyday lawn renovation; instead they’re designed to make you the hero without big league spending.

Identify areas needing to bulk up, making sure spots of bare soil, dead grass or weeds are prepped before over seeding.  “Don’t plant into a patch of weeds.  Dig them out, rototill them up, or use a weed killer before you seed.”  If using a weed killer, check the label to make sure you can seed grass after it’s applied.

 Remove thick mats of grass or weeds before you plant, then run a core aerator several times across the area, poking a lot of holes into the soil.  Rake up the area to rough it before planting.

Under a time crunch, choose your grass wisely; not all germinate and establish quickly.  Perennial rye is the go-to grass of choice for the pros, since it can be coaxed to germinate in a week if temperatures are ideal.

For fast results, pre-germinate the seed by soaking it in water for 24 hours.  “We put a mesh bag of it into a big trash can of water, soaking it to pop the seed coat. It’ll give you a two day head start on getting the seed out of the ground,” he said.  Once soaked the seed is perishable, so drain the seed after 24 hours, fluff it up and sow it within two days.   

How you plant is the difference between rookie and pro, says Kurcab, so err on the side of aggression.  “People think you just throw it on the ground and it grows, but grass seed needs planting.  Get the seed into the soil by spreading it thickly – about five or six per square inch – then sprinkle a half-inch of soil over the top.  Seed is cheap, don’t go too light with it; though this is three times the recommended rate for new lawns, we’re doing a quick fix to get you through the picnic.” 

Rake the area to get the seed into the core aeration holes and break up the cores.  Then lightly roll the area to press the seed against the soil (rental firms may have rollers available). 

Once your seeds are in, water them thoroughly for the first two days, keeping the area slightly squishy.  Then water the area three times daily for 5 minutes for two weeks to keep the top half-inch moist.  After the seedlings are up, slowly wean the water away until you’re watering it along with the rest of the lawn.

Fertilize it when the seedlings get a half-inch tall with regular strength fertilizer.  You’ll need to mow more often to keep fast-growing seedlings even with the mature grass, but no pain, no gain.  And it’s a small price to pay for a winning picnic.

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Australian researchers from Queensland University announced that the smell of freshly mown grass sooths stressed out rats and mice.  After a hard day running the wheel, one waft of the just clipped green sent the rodents into Zen-like states, improving their memory while lowering their anxiety. 

The problem is, none of those squeakers ever had to deal with an actual lawn.  After a summer of clipping, edging, raking, and watering, the last thing the lawn evokes is a calming sense of stress release.  That thin, sluggishly growing diva gets your blood pressure climbing, and a flamethrower starts looking like a serious option for better lawn care.

Give it – and yourself – a break by giving that grass a late season application of fertilizer.  The boost grass gets from the extra nitrogen will have it making and storing food for the winter, then using it for powerful growth in spring.  This simple act will have you complimenting, rather than cursing, your yard.

As long as your grass is green, the last shot of fertilizer can be put down in the first part of November.  This keeps the grass photosynthesizing as it heads into winter, storing the food it makes in its roots.  Once spring warms the turf, it greens up, becomes lush and dense, but doesn’t grow so quickly you need to mow often.

Any lawn fertilizer will do; you don’t have to choose a product labeled as winterizer.  The nitrogen is what’s important, so use up any fertilizer left from the summer.

While you’re feeling the lawn love, take time to put your mower to bed.  Disconnect the spark plug wire from the spark plug before starting, so you can drain the gas from the gas tank without risking fire from an unplanned spark. 

If you prefer to leave the gas in the mower tank, add a fuel stabilizer to prevent corrosion and keep the fuel fresh.  Replace the spark plug in your mower, change the air filter and oil, and your job is done.

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It lays outside, quietly hoping you’ll notice its hunger.  Rich, brilliant tones have settled to dull green, with a golden glaze coating the swath.  Sure, you still have to mow it every week, but the season of growth has left your lawn in need of a boost from fertilizer.    Thin yellow lawn

 September is the month for fall lawn care, and the most important aspect to lawn rejuvenation is a strong fall feeding.  Use a turf-builder fertilizer that has both quick and slow release nutrients.  All-purpose mixes have 16 nutrients needed by turf to be healthy – a balanced fertilizer goes beyond offering nitrogen, phosphate and potassium oxide (the N-P-K numbers). 

Lawns aren’t supposed to turn color in the fall, so if yours is taking on a yellow pall, you need to add some iron.  But our soils are so alkaline that you need chelated iron to apply to lawns that suffer from iron chlorosis.  Be aware that not all chelation formulas work in our soils, so look for ethylene diamine dihdroxyphenyl acetate (EDDHA).  The more commonly, and cheaply, available EDTA (ethylene diamine tetraacetate) is only active in pH-neutral soils – something we rarely see here in Colorado.  

 Nitrogen depends on temperature and moisture for release into the soil.  When we have warm days plus a few rain showers, lawns get a quick boost of food, and under ideal conditions, turf – an active scavenger of nitrogen – will take up the nitrogen within hours of it being put down.

This is perfect for lawns towards the end of September, because the quickly available fertilizer will increase turf vigor, and the slow release will continue encouraging turf rebuilding well into fall.  Thin spots

 Thin areas where the grass has died off completely can be over-seeded now.  To get the best results from over-seeding, water the lawn 24 hours before aerating.  Pass the aerator over the turf in two to three directions to open up many holes.  Immediately over-seed with the grass of your choice, but in general, tall fescues do not blend well with bluegrass, perennial rye or fine fescue because of its wide grass blades.

Grass seed takes a while to germinate, so keep humidity on the lawn for 14 to 21 days. 

Use starter fertilizer at the time of overseeding to feed the turf without burning the new shoots.

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