Bishop’s weed is a pesky invasive to kill

Question: Previous owners planted Bishop’s Weed. We are trying to get rid of it, but it keeps coming back. It is now getting into our lawn. How can we get rid of this for good?

Answer: Anyone who has or is battling this weed knows it is a difficult one to eliminate. It is classified as an invasive plant since it has moved into our woodlands and is crowding out native plants.

Continually hand pull and dig out the plants, rhizomes and all. This can eventually control this weed. Bag and dispose of this invasive plant to prevent it from establishing in a new area. This takes persistence and several years — something most of us are not willing or able to do.

Or, you can edge the bed where the Bishop’s weed, also known as goutweed, resides. Securely cover with black plastic in early spring as the sprouts appear. Leave in place for at least one full growing season. This smothers anything growing in the garden.

Once the plastic is removed, continue to monitor the bed for any stray plants that may sprout. Remove the sprouts, roots and all, immediately.

Several applications of a total vegetation killer applied when the plants are actively growing also can be effective. Start early in the season to increase your chance of success. Visit the Wisconsin DNR website for more info on this and other invasive species.

Q: Recently I learned that perennials don’t last a lifetime, much to my surprise. I always thought it was my fault something didn’t continue to grow.

A: Many factors, including the plant itself, determine its longevity. Some plants like peonies can last nearly 100 years, while others, like pincushion flower, are short-lived in our area.

Start by conducting an internet search for longlived perennials. Check several sources and compare the results. Then look to local resources.

I included long-lived perennials and their required growing conditions in my book, “Minnesota and Wisconsin Getting Started Garden Guide” (Cool Springs Press, 2013).

Always check the plant tag or catalog description when shopping for plants. Avoid any labeled as “short-lived” if your goal is longevity.

Q: Last year some, not all, of my tomatoes did not fully ripen. I did have a lot of aphids in the garden last year and sprayed them with dish soap. Any thoughts?

A: Poor ripening of tomatoes can happen when temperatures drop below 60 degrees, if the soil is compacted and wet, or from yellow shoulder disorder. We are not sure what causes yellow shoulder disorder, but it appears to be related to adverse weather and soil fertility.

Start with a soil test before changing your fertilization program. Adding too much of one nutrient can prevent the absorption of others, causing different problems. As you observed, some varieties seem to be more resistant to the problem than others. Consider planting those if this is an ongoing issue.