Question
Hi Jim

Your response to Melissa's question came up in a Google query.  I thought your advice to her was outstanding, but my lawn specs are so different that I'm not sure how much your suggestions would apply to my grass problems.

I live in Omaha, NE (is that in a temperate zone?) and two years ago the lawn was in great shape.  A lawn care service's bid said my lawn is Kentucky Bluegrass.  Last year, my only problems were a couple of small (12" diameter) patches of crab- grass, in the large, unshaded back yard and uneven growth rates; about 4 days without mowing and small patches of grass in the shaded front yard would grow more quickly, giving the lawn a bushy look.

I neglected to perform core aeration last fall, but I did apply Sta-Green Winterizer pellets.  Since just this Spring, my yard has turned into a real eyesore.  This Spring has been relatively dry in Omaha, but the neighbors' lawns were green a lot sooner than mine, and I've watered in the weeks that it doesn't rain. Even worse, I developed a dandelion problem that didn't exist in the fall. The crabgrass patches are bigger than ever, and the "bushy" look is back with a vengence.  The front yard has very visible demarcations between the darker, fast growing grass and the more dominant, lighter grass that is growing more sparsely (winter's dry mat shows through still).

I've aerated manually, mowed regularly, and I'm in the process of hiring (semi-)professional help.  One lawn service's bid identified the dandelion problem, and noted the presence of tall fescue (the fast growing grass, I presume).

Here are my questions:
Should I lower the mower blade from 3" to 2"?
Should I spread Kentucky Bluegrass seed?
Is core aeration a high priority, or can I defer until the Fall (cost of kid's braces and all)?  I've tried raking up the winter mat, but is a powerake a lot more effective?
I'm addressing the dandelions with post-emergent sprays, but can/should I still apply preemergent pellets to help the lighter grass along?
Am I better off promoting the tall fescue (the lawn service's bid said that tall fescue is hard to treat), since it turned green sooner and is thicker, even though it grows so fast?

Many thanks,

Bill

Answer
Hi Bill,

>>"...Is core aeration a high priority...?"

The need for aeration events is entirely dependent upon the physics of your top-soil.
Unless you have a top-soil which is compacted and/or particularly high in clay content, you should not have to make aeration a regular task. It is very rare that most residential homeowners make aeration even an annual task and their lawns do fine.  Work instead to add some top-soil amendments in the form of organic matter (humus, composts, manure, etc.) to make the soil more well aerated, friable, and moisture retentive.  If you can toss in several pounds of mail-order earth-worms, this would to all the aeration for you 24/7 and also add to the fertility factors of the root-zone.

Having thatch accumulation on northern lawns can be conducive to fungus diseases.
I recommend keeping thatch organic matter off the lawn and composted. This means collecting the grass clippings with each mowing event. Use the grass and garden vegetation from your lawns and gardens to make compost (see links below for info).  Add mature commercial or home-made compost to the summer 'Hot-Spots' in the lawn as a method to return the organic matter and minerals the mowing removes.   Using compost every so often has all the benefits of thatch while avoiding all the potential problems.
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>>"...lower the mower blade...?"

The recommended blade-height for KYB is 1.5-2.5 inches.  In times of drought, it may help to keep it higher for the mulching effects.
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>>"...Should I spread Kentucky Bluegrass seed?"

KYB is considered a cool-climate grass-type and the seed is typically spread in the fall, around Sept-Oct.  However, you can usually try to get any turf-grass seed started PROVIDED there will not be weather extremes and also provided you can keep the seedlings well hydrated.  Just a few hours of warm winds can make seed-starting impossible.  In late spring you may try to start areas you can keep well watered and also use mulches such as straw, hay, peat-moss, or a commercial mulch to help prevent the effects of drying winds.  
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Use a pre-emergent herbicide as directed with the product and read the label to know what to expect.  Some formulas are advertised as 'Preventive' but this does not necessarily mean they contain a valid pre-emergent chemical.  This type of chemical keeps the weed seed (or any seed) from sprouting.  This can give optimum and efficient weed-control when timed properly.  You cannot get your wanted turf-grasses started from seed IF you have an active pre-emergent chemical in the top-soil.  So, you have to study the label and plan ahead with the calender to get the best use out of this type of chemical.  If weeds are just few and spotty and only of several types, it may just be more practical to use a POST-EMERGENT chemical (such as 2-4-D for Dandelions) than to use the more expensive pre-emergent products,...especially if you will be trying to get wanted turf-grass seed started.

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If you persist in having lawn appearance problems, you may want to consider up-grading to a new super-hybrid grass-type rated for your locale and Horticultural Plant Hardiness ZONE,...or perhaps changing to another grass-type entirely.

Old cultivars of Kentucy Blue-grass are noted for having some difficulties and unique syndromes.

Currently, cultivars of TALL FESCUE such as 'SR-8600' and 'Rembrandt', are rated the best as cool-climate grasses.
These have out-performed hundreds of others in university testing for hardiness, drought, disease, and shade-tolerance. I recommend Tall Fescues over KYBs.

A soil-test may discern any chemistry problems that are causing any difficulties.
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Lawn Science Seed and Seeding Resources:
 http://hometown.aol.com/eilatlog/seed/seedings.html
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I Hope this has answered your question(s)!
Have a great Summer.
___JIM Gibbs,
   Microbiologist

Visit my Lawn & Gardens webpage for more facts and links:
http://hometown.aol.com/eilatlog/lawnol.html

Your Questions and Comments are welcome at ALLEXPERTS.com
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