Q. In the past 6 or 7 years, a blue-flowering weed has overtaken parts of this neighborhood, and it is highly aggressive. It thrives in shade. It has 8″ (more or less) tapered basal leaves. The flower stalks are round, from 18″ to 3′ or 4′ tall, and branch at the tips into clusters of small half-inch bright blue blowers with white centers. The leaves and stacks have a fuzzy feel. Seed production is prolific, and the roots send out stolons. The mother root develops a thick white fleshy vertical rhizome-like form as much as 1′ deep. After blooming, the plant quickly turns into a grey mildewed mess. The fuzz and the after-bloom mess remind me of mertensia. What is this? How can it be controlled without chemicals? I cut the flowerheads before seed forms, and dig as much of the root as possible. Beverly Isenson – Steilacoom, WA
A. I have these in my yard as well. They are botanically Pentaglottis sempervirens. Common names include pentaglottis, evergreen bugloss, alkanet, and green alkanet. It has become a weed in many parts of the world (native to France) because the roots were used to make red dye. The actions you have taken so far are the non-chemical controls of this plant. Depending where the weed is you can dig them back and then put down a weed fabric barrier. I have found that the “mother root” as you call it will go much deeper than 1″ as you indicated. These fleshy storage roots break easily. If you don’t get the entire root you will get re-sprouts. I have seen re-sprouts from root fragments as deep as nine inches. So make sure you are using a weeding tool that can get deep down along side the root like a STAINLESS STEEL DIGGIT WEEDING TOOL or a STAINLESS STEEL HORI HORI KNIFE . You can also spray with a glyphosate based herbicide.