This is not comfrey.
Online plant ID groups can be frustrating. They usually consist of a few experts floating in a sea of people casually interested in plant ID. On one hand this is great – it gives gardeners and amateur botanists the opportunity to hone their plant ID skills and get feedback from experts. On the other hand, unfortunately, is the common situation that occurs when the knowledge of the experts is drowned out completely by a flood of inexperienced voices who seem to think an uninformed majority opinion can overrule said experts.
This happens a lot with comfrey; or perhaps more accurately the relatives of comfrey. The plant pictured above is not comfrey, despite the well-intentioned majority of people who insist the contrary almost every time it appears online. It is not borage either, another less popular but prevalent misidentification. It is actually a relative of comfrey called green alkanet, Pentaglottis sempervirens, a highly invasive weed that is making its way across the west.
Green alkanet is not native to Oregon but it grows excellently here without human intervention, already setting the stage for a full-scale biological invasion. It’s a perennial plant with the reproductive ability of borage combined with the deep taproots of comfrey that is at ease in both full sun and shade. It happily grows through the winter, the lush growth smothering dormant and seedling native plants. Green alkanet easily weathers Oregon summers, thanks to the large taproot, and produces large amounts of seed from blooms that appear continuously from early spring, blooming even in early March, until the first hard frosts. That is a lot of seeds. These seeds hitch rides on clothing and animal fur, distributing them far and wide.
Control is difficult. The plant can grow right up through mulch, even layers more a foot deep. Repeated cutting seems to weaken it, though this is not as effective as removal of the whole taproot and can take years of repeated cutting. So far the easiest way to control it, at least in my experience, has been cutting with my hori-hori a few inches into the soil, removing the top, placing several layers of cardboard, and then mulching over the remainder with wood chips. I leave the tops in the sun before composting to prevent resprouting, leaving them in the garden paths to be crushed underfoot. But even then it still comes back, to the point of me contemplating herbicide use.
It has a few uses – bees do like it, and it is useful in dying cloth. But it is not worth the pain and risk to native ecosystems, which is why it is so frustrating when it is repeatedly misidentified as the more innocuous comfrey, the dubious permaculture wonderchild. This leads to misinformed gardeners encouraging people to leave it in their gardens despite obvious signs that it is spreading out of control. Some are even reprimanded for encouraging its removal. This puts the plant in a prime position to escape cultivation, which it has done across Washington and parts of Oregon.
Once the plant does escape it runs rampant through native ecosystems. It is capable of choking out even the more vigorous natives, like milkweed, and can handle even the more extreme wet and dry environs the PNW has to offer. Herbicides are the preferred weapon of state and federal agencies and it’s hard to blame them, as the plant vigorously resprouts from even tiny fragments of root and shrugs off heavy mulches and even fire with impunity. Why not cut the invasion off at the source?
If you see ‘comfrey’ or ‘borage’ that is spreading quickly through your garden, take another look and get a real expert opinion. Carefully observe the flowers, which easily betray alkanets true identity. Also make sure it is not the lovely wildflower, Pacific Houndstongue, which looks similar. Once you have confirmed a plant is green alkanet, remove it from the garden and destroy it completely to prevent infestation. Your local ecosystem will thank you.