I bought 2 Bonnie Plants lavender plants a few weeks ago, before it was warm enough outside to start gardening. Now that it's warmed up some (I'm in NE Ohio), I want to plant them in pots or a planter box on the patio. I've been reading up on soil requirements for lavender - more alkaline, well-draining - and I'm trying to determine how to mix a suitable soil for them so they'll thrive. (There's really nowhere in the yard to plant them in the ground where the dogs won't pee on them, so they have to go in a planter on the patio.)

The soil I've been using for my other planter boxes is Nature's Care Organic Raised Bed Soil, but that's for my tomatoes, peppers and strawberries. Given the general composition, I figured the soil would be more acidic; but I wanted to test, just to be sure. So I got a soil pH tester from Home Depot. (I did read a number of threads on the general unreliability of home soil pH testers before I bought, but some folks have apparently found success with theirs, so I thought I'd at least give it a shot.)

To be specific, I got a Burpee Garden Helpers Electronic Soil Tester. (For those of you with experience with electronic soil testers, maybe even this specific one, I want you to follow the link and look at the photo of the item on the website. You'll get a kick out of it. *smh*)

The instructions say to collect samples of soil from where you plan on planting and put them in a container, to a depth of roughly 6"; add enough distilled water to equal the amount of soil in the container. Let this slurry sit for 15 minutes, then pour off the excess water; insert the prongs of the soil tester into the soil, turning the tester to the "pH" setting, and let the tester sit there for 2 minutes. Then note the reading. (Seems simple enough.)

Except that, when I did this, it didn't do ANYTHING. No reading, nothing, nada.

I remembered several folks having the same problem, and that one person suggested rubbing/scraping the probes with a scrubby or a brillo pad. So I tried that, and inserted the tester into the soil again. Lo and behold, I got a reading! I was so excited! My soil read just a little under 5.5 (maybe 5.3?).

Then something funny happened. I took the tester out and wiped it clean with a paper towel to take a picture of it (I was going to post pictures in this post, but then decided it wasn't necessary); when I put the tester back in the soil and let it sit again, the reading changed, to about 6.0. I left it sitting there for a good while this time (I was helping my husband with dinner by that point), and when I went back to it again, the reading seemed to have stabilized at 6.5.

So, the soil is acidic, as I expected, although how acidic seems to be debatable; but the moral of my story seems to be that the Burpee soil pH tester is a crapshoot (as a ton of folks on GW have already intimated).

Anyway, I thought I would share.

All of that being said, does anyone have any suggestions on a suitable soil for lavender plants in a planter box? Is there a ready-made mix I can buy at a store, or can I use the soil I have and just add lime to raise the pH and gravel and perlite to improve drainage?

chaparralgirl