Seattle Area Lawn Care Tips

copyr Landscape Specialists 2002-2016


Grounds Maintenance is a major budget item for most property owners. For this reason the following factors should be carefully considered.


Frequency and detail are the major cost factors on a given area of lawn. In Seattle, a lawn can be maintained with 24 or less cuts per year, providing it is not over-fertilized. The mowing frequency varies during the growing season from March to November (see our grounds maintenance calendar).

Details include edging along sidewalks, walkways, curbs, driveways, stepping stones, and flower beds; trimming along walls, beds, around posts, fences, and anywhere else a lawnmower won't reach. Intricate lawn area's can really slow down the job.

Mulch the Clippings

Clippings add organic nutrients back into the soil. This is a free high quality source of nutrients and soil building organic matter. (See our Equipment Tips webpage for mower recommendations and tips on mulching techniques). When mulched properly, clippings are not visible and do not contribute to thatch buildup.


There are three warm, dry months in Seattle; July, August, and September. The need for water will vary depending on amount of exposure to sun, type of grass, soil, and thatch. The cost to water one inch per week for 12 weeks is on average a small part of a total landscape budget. Failing to water will generally encourage less desirable turfgrasses, or weeds, to take over.

Some lawns will come back if they are not watered. Some will require costly renovation to break up crusty soils that may develop. You can observe the various effects on any neighborhood street in late October or May, when grass should be growing nicely from normal rainfall.

Weed control

Cost and effectiveness must be balanced with the potential for environmental damage. Monitoring is the best policy , using the safest SPOT CONTROL herbicides available for unacceptable levels of weeds. I personally do not recommend use of any toxic products which require registration by the EPA.

Corn Gluten is a pre-emergent weed suppressor that is non-toxic. It is available from Walts Fertilizer in Seattle. I am not sure if it works.

There are weed-control products available off the shelf which claim to to be safe, or safer, then products known to cause cancer etc. and environmental problems. Make sure they are labeled for the use you intend. Follow the label instructions.


Most lawns will benefit from one application per year, or maybe two, at 1 pound nitrogen per 1000 sq. feet.

Use slow-release fertilizer. I apply in early June and early November. Grass clippings left on the lawn give an added benefit equal to 1 application of fertilizer. Overfertilizing or fertilizing in early spring will result in additional mowing and may cause other plant health problems.

We use "signature" brand fertilizer with 18% nitrogen. It is available from the Ace Hardware store in Auburn. It has good proportions of slow-release fertilizer and micro-nutrients.

Corn Gluten seems like good product - probably a late spring or mid-summer fertilizer - it is available from Walts Fertilizer. It does not provide micronutrients, or a favorable n-p-k ratio, but is a good source of organic nitrogen.

Moss Control

Moss control products are best used in late March and early October. This allows grass to quickly fill in. Always read and follow label instructions. Products containing Iron should not be used on hardscapes - it may cause staining of surfaces especially new concrete. Be aware that some moss control products also contain nitrogen, so adjust your regular fertilizer use accordingly.

Use specially labeled products (not iron) for moss control on hardscapes. Follow label instructions. Scrape as much away as possible first. The dead moss eventually should weather away after moss-control application. I would use a pressure washer in cases where the residual dead moss is visually unacceptable.

Lilly Miller "Worry Free" seems to be a good product that can be used on lawns and hardscapes. If a lawn area is more moss than grass, it will need overseeding. We have had some success in seeding directly over freshly killed moss and then topdressing with compost. Otherwise rake the moss out with a rigid tine bow rake.

Try not to loosen too much topsoil, as topsoil beneath moss is good quality stuff. Apply moss control to remaining moss if needed, then overseed and topdress as above. (see renovation, below).

Lime (or other soil sweeteners)

Soils in Seattle are generally very acidic; chemical fertilizers also add to soil acidity. Lime reduces soil acidity. This helps turfgrass by providing a better environment for beneficial micro- organisms and earthworms, which aerate the soil and break down thatch. A lime application is recommended once a year at 20#'s per 1000 sq. feet. Lime or other soil sweetener is best used in a pelletized form to avoid dust. Any time of year is probably ok, but I would avoid summer applications to take advantage of available rainfall at other times.

Caution: Lime drifting onto rhody's, azalea's, and other acid-loving plants may damage them.


Aeration can benefit certain lawns which are compacted or have a water-resistant thatch layer. If the soil beneath the lawn is getting wet after a good rain, the lawn probably doesn't need it. The cores should be left in place to avoid removing topsoil.

To be effective, ten percent of the surface area should be removed. This will require several passes of the aerator.


Lawns that have deteriorated through poor maintenance or disease problems may require any combination of dethatching, aerating, top-dressing, and overseeding to restore them. In Seattle the best times for this are late March to early May and early October. Top quality grass seed of the proper type must be used. Due to the cost of renovation proceedures, try to target specific problem area's.

Grass seed will not germinate until soil temperature hits about 55 degree's Fahrenheit. This occurs around April 1st. After October 10th, soil temps cool and there may not be enough time for the seedlings to establish. It takes about 7-14 days for for seedlings to establish, and allow 30 days before mowing. The lawn will continue to thicken over time, and will require overseeding spots, that remain bare.

J&B sun/shade grass seed is the seed I recommend.


Most lawn diseases are caused by fungal organisms. Often they are hard to specifically identify, and few products are available to control them after symptoms appear. Usually proper maintenance and moderate fertilizer programs are sufficient control.


There are not many lawn problems caused by insects in Seattle. Cranefly causes damage but does not warrant pre-emptive control unless identified. - spot treat with least-toxic available control March thru early May if more than 25 larvae (tiny, skinny, wormlike critters) are detected per square foot. Problems are characterized by dead looking patches or area's of sod that are easily lifted from the soil.

Otherwise, insect control will be counterproductive as beneficial earthworms, pollinators, predatory insects, and micro-organisms will also be wiped out. Pesticides have a greater potential than herbicides to harm human and animal life if used improperly.


Gophers may be a temporary nuisance as they sometimes move on to greener pastures. The mounds actually make a good source of topdressing when raked into the lawn, but watch out for rocks when mowing. Overseed if nescessary. I suggest trying gopher repellant products rather than poison or traps. Killing gophers outright may invite invasion from neighboring infested areas. The electronic devices i have tried do not seem to work for me.

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