There are very few soils that are "unusable" just soils that are abused. Putting plants in pots in the ground is not a very good idea since it will limit growth too much, but the soil can be made into something that will grow both those blueberries and a good healthy lawn. The University of Rhode Island does not do soil testing, but you could contact either UONN or UMASS (I don't remember which off hand) and they will, plus these simple soil tests,
1) Soil test for organic matter. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. For example, a good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top.

2) Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drainsâ too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up.

3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart.

4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer your soil will smell.

5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy.
may be of some help.

I also have 10 gallon wide black plastic pots that contain blueberry plants and plants that don't do well through the winter in my zone.

I'm curious about the blueberry bushes not doing well in your zone. I grew up in New England and there were wild blueberries everywhere. We picked them in the woods around our cabin in Maine. Why can't yours go survive the winter?

If you look closely the OP said blueberries AND plants that don't do well in winter.

I have limited experience here but I can offer this: I sink some tropical house plant pots in a shady bed in the summer and dig them up in fall. This works for amaryllis bulbs and some others. It gets them out of the house into some fresh air, they get watered and they beautify the bed. I generally sink them all the way and mulch over everything so the pot is not visible. It works fine.

Thanks for the responses.

Plants in pots suffer from the summer heat, so this is the least I can do.

Some plants have specific demands in soil.

Less hardy perennials that do fine in the garage will die outside during the winter.

Kim, I'm not looking for an argument on what is my very best choice between pots and the ground but I appreciate the effort with all the information you supplied. Maybe my post was misleading. I thought I needed help with the ins and outs of planting pots. I do have plans in the ground and they quite nicely. I also have raised beds :). The blueberries are at most two years of age and they are medium sized hybrids, not the highbush type, and I'm not committed to their final destination or improving that area of the soil for acid loving plants.

dekeoboe, I love wild Maine blueberries as well :) They are so hardy, and I have grown these little guys where I live. I also am trying to grow the European wild blueberry (vaccinium myrtillus) this year.

Toxic, thank you.... One of the most relevant source of information I found was on YouTube where 'master gardeners' (whatever that is) buried wide Blueberry pots in the ground... They placed gravel on the ground beneath the pots for additional drainage. Maybe the only thing I have to worry about is drainage after all. My thought of options at this point is to dig the holes in a pattern, test drainage, put down the pots, and mulch the pattern so pots are hidden, just as you have.

To me at least this sounds great as I can play around with the landscape. I also have plants that will spread like horseradish and hops in wide pots, and will be easier to harvest and control in pots.

This post was edited by bardamu on Mon, Apr 28, 14 at 16:00