Anonymous wrote:I would have your soil tested before you do anything. Your existing plants probably just need more water right now. Bleeding hearts go dormant in the summer (i.e., shrivel up and look like cr@p), and hostas are pretty darn tough except deer love them.
You don't want to put more than an inch or two of additional soil or compost over areas with trees because this is very bad for the trees. Compost may provide more bang for your buck than topsoil. Leafgro is one brand of compost, and it's worked well for us.
Don't move the soil from your patio project--it's going to be even worse than your soil under the trees.
Once you have your soil tested, let that guide your plant choices (i.e., if it's acidic, rhododendrons and azaleas should do well, if it's alkaline, find out what plants would do well for you). Then when you dig holes for your new plants, dig the holes twice as wide as the rootball of your new plant and fill the hole with half compost (Leafgro) and half old soil you dug out of your hole). Be willing to adjust where you put the plants if you run into a big tree root.
I wouldn't bother with getting a bunch of topsoil shipped in as long as your trees are doing well.
+1 The new soil around new plants --easy-- just buy a bag of soil when you buy the plant. Also composted manure does wonders for the lawn. Spread it thinly (is sanitized) Some water and fertilizer does wonders also.