One side of my backyard is overgrown with lily of the valley that came from my neighbor’s yard under the fence. I try digging them out in the spring when the ground is somewhat workable but I always seem to lose the battle. The soil is mostly clay and very hard to work with. I would like to get rid of them; any advice? B.P., Taylor

The creeping rhizomes of lily of the valley (Convallaria majalis) allow for rapid spread even in mediocre conditions. The clay may be hard for you to work in, but it hardly deters their persistent rootstock. Even a small piece of lingering rhizome can erupt in basal leaves. Lily of the valley spawns a love-hate relationship from gardeners in spring. They are one of the earliest fragrant white flowers, but once bloomed, the foliage browns out and dies back. In the meantime, the rhizomes grow and further invade areas of established lawns and gardens.

As they are in your neighbor’s yard, you will have to put a seamless metal (sheet roll aluminum) or stiff plastic barrier at least 18 inches down into the soil along the fence on your side where the plants grow. Stake it against the fence to prevent the rhizomes from pushing and bending the barrier. Diligently spade fork the rhizomes out and reduce the amount of shade and moisture in that area, which they prefer. Be aggressive in your approach by target spraying with an herbicide, such as glyphosate, any leaves that break the soil’s surface. Do not plant other plants in this area for a season while you do battle. Any compost or granular fertilizers you would use for your plants will only feed leftover rootlets. Perhaps you can negotiate with your neighbor to move the lily of the valley to another part of their yard where it won’t invade your yard. If not, practice patience and persistence to get rid of this invasive perennial.