I have a small back yard that is surrounded by lots of trees. Even perennials such as hosta are doing poorly. Do you recommend that I plant them in pots in the soil with room for the roots to grow in an effort to “block” the tree roots from stifling the plants? If so, how do I do this? Would I need to cut out the bottom of the pot? And would it be okay over the winter in a pot, even if the pot is in the ground?
Your poor hostas! They are desperate for moisture and nutrition. The roots of the trees surrounding your garden are using up all of the nutrients and moisture, leaving your perennials with little to sustain them. Most tree roots are located within the first 6 – 12 inches of soil and they extend way past the canopy drip line of the tree.
Since your hostas have been planted already, I would suggest leaving them in place and giving them twice as much water and nutrients than you normally would. By digging them up and replanting them in pots and sinking them back into the ground you will disturb even more tree roots especially since you will have to use quite large pots to accommodate the future root growth of the perennial.
An alternative would be to plant your perennials in pots and design your garden with these on top of the soil or on hard surfaces. Your perennials can be kept over winter by following some some of the strategies outlined in the attached web site below. You will not want to follow the recommendation to sink your pots into the soil for the winter since this would again cause too much damage to the tree roots, although this method is very effective in areas where there are no roots.
Perennials for Shade and Part Shade: A Toronto Master Gardeners Guide
To see another list of perennials which can survive in dry shade, click here.