Overseeding in zone 8a: too late?

5 years ago

TLDR: Overseed in zone 8a (PNW) during a week of moderate rain , or wait until early October and risk frost and weed resurgence?

Longer version:

Bought a house in August near Seattle and the HOA (mistakes were made) is already on my behind about the sorry state of the yard from the previous owner. Looks like I'm getting into the grass game, like it or not.

Front yard space is maybe 1800 square feet, but (was) pretty epically overgrown with dandelions, crabgrass (?) and moss. Really didn't want to use aggressive chemicals (two kids and I'm reading about reproductive and cancer issues from long-term exposure) so bought a Fiskars stand-up weeder and have been thinning the ranks daily.

I figured it was time to overseed. Spent Saturday getting supplies: thatch rake, manual core aerator, seed spreader, good sized bag of Viggoro seed, Lily sweetener, 2 yards of compost, 2 bags of Milorganite (for the back-yard, too). Spent most of Sunday further thinning weeds and manually removing thatch and moss. Now I've got a bunch of bare spots and a few patches of grass, plus some remaning smaller weeds.

My initial plan was to sweeten the lawn, water and wait a day, then aerate, topdress with 1/4" of compost and then seed, followed by the Milorganite (watering frequently to keep moist, of course).

Now, though, I'm expecting a week of rain (maybe 1/4 - 1/2" / day). We'll apparently be drying out around October 2nd or so. My question is:

Can I proceed with any/all phases of this plan in light of the rain, or should I wait for it to dry out? I'm concerned about frost; our first frost average is around 10/6. Feeling like the longer I wait, the more danger the seeds/plants will be in. I'm also worried by leaving my newly-dethatched yard open I'll be inviting the remaining weeds to spread like wildfire and fill in the gaps, undoing my diligent removal efforts and inviting further HOA wrath (boy howdy, were mistakes made).

Thanks in advance for helping a noob out!

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Comments (3)

gardengal48 (PNW Z8/9)
5 years ago
You are rapidly approaching the end of the overseeding window here.........mid October is generally considered the cut-off date. But given that you can probably skip most of your list of to-do firsts, you should still have plenty of dry time to get the seed down.

If by "sweeten" the lawn you mean applying lime, that is likely not necessary. Our soils are only slightly acidic and well within the pH range preferred by most turf grasses.

I hope the seed you purchased was formulated for this area - our climate places some peculiar demands on seed types. I generally avoid any national brands and look for local suppliers, typically sold at garden centers and better feed stores, not the box stores.

Manual aeration is a waste of time and effort. It just doesn't accomplish anything productive. Some believe that any physical aeration is unnecessary, preferring surfactants instead, but I have not found that to be useful at all. However, a power core aeration can be very beneficial but should be done with some lead time before seeding, so could be tight fitting in. No issues skipping this step. It can be done next spring if desired.

That just leaves seeding. Cut the lawn as short as you can and carefully rake up all debris. Apply the Milorganite, then seed, then cover with a thin layer of compost, no more than a 1/4 inch. Water as necessary to keep moist, which may be hardly at all in our climate :-) You can repeat this process again in spring (mid April to mid May) if you feel necessary. Unlike most of the country, we can get away with spring seeding because of our (usually) cool summers.

10/6 is awfully early for a frost around here in a zone 8. You could see it that early in the foothills but those are considered a zone 7. Typically it is late November before the Puget Sound basin zone 8 sees a significant frost and the closer to the Sound, the later that date gets. I've lived here my entire life and I am still harvesting tomatoes in October! I don't think I've ever seen a frost that early.
Just Someguy thanked gardengal48 (PNW Z8/9)
Just Someguy
Original Author
5 years ago
Thank you so much! I got the seed in just in time for a reasonable rain to help speed the watering process along. Keeping my fingers crossed that things pan out. I really appreciate the help!
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dchall_san_antonio
5 years ago
Okay so here's why the USDA zones are no help in dealing with lawns. I live in Zone 8a in the hot, Texas Hill Country. My situation is quite different from yours...except for winter low temps.