Per your request, I'll stick to the usability and won't even look past the visual...
So, it looks great on mobile. On my Fire HD, it is crisp, clear, and nice to look at and read. Thank you...
From my laptop, it looks very good. The font choices and colors make for an easy read.
I'm not entirely sold on the over-sized discount offer. Looks good on mobile, a bit overwhelming on a larger screen, but it's not altogether unpleasant. It might be that specific bright red that's a bit much. Extra points for not having a slideshow.
Tips & Tricks seems the wrong title for the content box? Q&A might be more appropriate, but maybe I'm missing the concept you're shooting for with the redirect to your other site.
The content boxes with the white font on green background are a good example of execution. It works great in small areas, such as yours. Full pages, not so much.
Lawn Page: I like the inclusion of the block quote/whatever in the the green box "We know that is just about opposite to every other offering in the market, but there is a catch."
Great way to break up content.
And then I hit the big, red stop sign. lol There's that FF0000 red again. To my eyes, jarring. It could be toned down a bit so as not to be so harsh, but we're playing in the subjective area. Could also be that it's one of the original, web safe colors, and those tend to have a dated, harsh look to me.
From a marketing standpoint, I'm not big on telling people your route is full or you're no longer accepting clients. Is this for all services? If it's not, what if I take away that it is and don't bother contacting you? To me, any time you can get a high-touch experience with a potential customer, you do so, even if only to tell them no. If I don't fill out your waiting list form you don't have my contact info to market to me in the future.
Love the logo. I just did a site that was the same crisp green on white and it's one of my favorites. Clean, modern, easy.
Footer design/navigation looks good. One thing that does bother me with LCO sites is the over reliance on green and the usual headers/footers that tend to be used, including the grass/roots image. BUT... you used a crisp, clean, high-quality image, and it makes me like it. lol For those that are wondering about the difference between a mediocre site and a very good or great site, the footer image is a great example. Image quality is everything. Anything less and I would think it cliche. It's not, and it lends itself nicely to the visual pop that the rest of the site has. I could probably write 2,000 words on this one, but you get the gist.
The offer call-outs on the Bug page look really nice.
I'd change up the visual cues of the Bug page and the Home page so that the visitor knows they did change pages.
Tree page art is nice. It's inconsistent with the rest of the art you used, but I like it a lot.
Weed page... as I go through the site, I look forward to seeing the images you've used so far. The Weed pic underwhelmed me as it doesn't meet the visual bar you set on the other pages.
Contact page form could use a visual punch up. The side "contact" photo is a bit of a deviation again, so I'm not sure if it's something I should be taking issue with or not. Really, it comes down to picking nits as the overall, visual execution is well done.
I have a crazy busy schedule so I didn't actually read the content, but the visual appeal is what made this the first LCO site I've added to my Pocket reader to revisit on any of the dozen flights I'll be on in the next week.
OOOhhh! Found something I really don't like. The grass border around the service area map.
Only real recommendations would be to work in some photos, or other block quotes or call-outs, to break up some of the content monotony/fatigue that can come with the bright white canvas territory. You might also want to add some internal content links to your relevant pages. Sweeping for grammar/sentence structure/punctuation with a second set of eyes would be something you might want to do. When I did a couple of random, quick text scans, I noticed a few issues.
All in all, that's on the Mount Rushmore of Lawnsite DIY efforts. Looking forward to seeing it as you progress.