My understanding was that it did not become activated until the soil temp reaches about 60 degrees. I would like to know that answer myself.

As a rule of thumb, there is very little chemical/biological activity when the soil is 40 degrees and almost none when it is frozen.

If the soil contains clay, it will retain phosphorus, potassium, and the ammonium form of nitrogen (which is probably what you have, check the label). Bacteria work on the ammonium and change it eventually to nitrate, which can wash out of any soil that is heavily irrigated. The change to nitrate happens slowly at 50 degrees soil temperature, but rapidly (maybe a couple of weeks) at 70 degrees.

I think Osmocote releases fairly well if it is just lightly mixed with the loose stuff at the soil surface, then covered with 3" of mulch. 6" might be too deep to be optimal.

Thanks, Michael. I just finished going ahead and digging the Osmocote in (along with tons of coffee grounds from the hospital where I work), but since the soil is nicely friable (not soggy, not dry), I thought I'd just leave it that way for a week or so before I water it in. Only worry is that I probably messed up a lot of the roses' roots that might have been in the top 3-4 inches. I figure, it'll aerate the bushes a little (oxygen) and force the other roots to go deeper. Am I wrong? still expecting sun for the next week and temps. in the high 60's here in Marin County.

A lot of the fine roots are in the top 3", right up to the surface, if mulched. That's why I don't do much scratching, much less digging. However, they will grow back pretty quickly. In the North, the shallow fine roots are damaged by frost heave each year, but grow back.

I also live in Marin County, and the high temp here in San Rafael yesterday was 79 degrees, and this morning when I first went outside at 8:30 it was already 70 degrees, and obviously heading for hotter! We don't haver air conditioning, so I ran around our old Victorian house closing all of the shades & windows, which is my summer "house stay cool" regimen. I don't know how many days of this it takes to warm up the soil, but I figure it isn't getting any colder!

I use Osmocote also. I am lazy, so what I do is weed around the roses, prune the roses (repeat bloomers, that is) in Feb (when they are already leafing out and/or starting to bloom), feed with Maxsea (liquid), throw Osmocote (you can actually get a 8-9 month version on line in larger bags, which saves $) on the soil, and cover it (WITHOUT scratching it in) with at least 2 inches of mulch or compost, and then watering.

That's it - that's all they get until Fall, except of course for additional water in our dry summer. (Of course, we haven't had any rain for 6 weeks, and it is hot NOW, so today I am going to have to water all of the pots, and if this keeps up another few days, we will have to turn on the irrigation system!)

Jackie