I have a west facing bed underneath a Scot’s Pine which is half goutweed. Is there a small to medium size pretty shrub that I can plant in it that can out-compete and survive in the encroaching goutweed?
Thank you for contacting the Toronto Master Gardeners. You have a rather delicious problem: a large shady Scot’s Pine that creates acidic soil with its dropped and decomposing pine needles, and a carpet of goutweed (Aegopodium podagraria).
A suggestion for a flowing shrub that meet your requirements of being pretty, able to thrive in acidic soil, grow in the shade on the west side of the tree, and able to survive the encroaching goutweed — with some help — is a rhododendron or an azalea. Choose a cultivar that will not grow too high. The shrubs should be planted as far as you can from the tree so that they are not growing in deep shade. Water well after you have planted it and for the next few weeks as it settles in.
I also suggest that once you have planted the shrub, that you mulch it very heavily (at least 8″ of mulch) with shredded cedar or shredded pine bark to help smother and hence control the invasion of the goutweed. Create a donut of the mulch so that it is spread quite far out from the shrub, but is not actually touching the woody stem.
I hope that you find a shrub that meets your needs and gives you joy.