I have 16 wooden planters on my deck. I have horses wandering around the
acreage who would eat anything planted down on terra firma, so my gardening
is pretty limited to these planters they can't reach.

They are 3' X 1.5' in size. They are 5 years old now and the soil level has
dropped enough that I want to raise it. But I have a lot of perennials like
lavender, daisies, etc that were cut back properly and still live here and
there in the planters. In the past, I would buy mainly annuals to supplement
the resident perennials. So, experts....what would be the best way for me to
raise the soil level without just uprooting everything and starting all
over? Do I just go out now and buy enough soil to pour over the top, or do I
wait until the perrenials get high enough so they wouldn't be "drowned" by
the addition of the soil? Or something else altogether??

Thanks for any ideas

Laurie