Goutweed - sometimes known as bishop's weed, snow-on-the-mountain, ground elder or goatweed (yes, it is sometimes spelled this way – it got its name from how much goats love eating the stuff!) – has been called “pernicious as hell” and so “successful an adversary as to nearly be respected.”
Originally from Europe and Northern Asia (the fact it thrives in Siberia should tell us something), goutweed hitched a ride with settlers to North America, whereupon it was sometimes intentionally used as groundcover in new settlements, in addition to being used for food. Once established in an area, it invades into its surrounding areas and chokes out existing vegetation. Although no longer sold in most nurseries, it can still occasionally be found for sale as ornamental ground-covering at community bazaars and garage sales.
Zombies of the plant kingdom, this invasive species will survive, and even multiply, in response to anything but well-strategized full out warfare. In fact, more than one professional gardener has suggested moving, not completely tongue -in-cheek, as a legitimate response to a goutweed infestation. Here at THE SHE SHED though, where we thrive on the principles of perseverance and tenacity, we’ve found a few ways to vanquish the beast, and you can too.
The trick to understanding goutweed is that it spreads through its long white branching roots, or rhizomes. What this means is that while you don’t have to worry about it proliferating via seeds, simply pulling it is not going to do the trick. And, some well-intentioned methods of control will make it worse. Cultivating, for example, is a terrible idea. Because even the smallest part of the plant’s root system will sprout, simply plucking it or chopping at it does no good, and might even lead to spreading it.
That said, there are ways to deal with it...over time. Here’s how.
1 The Dig and Sift
For this method, understanding that the root systems can go down as deep as *gasp* a foot, the savvy gardener excavates a foot of soil off the visibly affected area. Also, be sure to extend your digging area by about a foot around the visible perimeter of the weed (just because the plants aren’t above ground, doesn’t mean they’re not quietly spreading below). Depending on the size of the afflicted area, once dug up, you can either dispose of the soil (always take it to the landfill), or meticulously sift through it for left over rhizomes.
Though some suggest simply mowing the afflicted area and then covering the area with a black tarp (make sure there are no areas where sun can get through) starting in the early spring and lasting through to fall, we advocate eradicating all visible signs of the weed first through pulling and sifting through the top soil, then pinning down the black tarp over the area (and an extra foot on all sides). If you can persevere through the poor aesthetics for the season, this method will starve the plant of carbohydrates made through photosynthesis. If you have established plants in the area, you will need to remove them as they will be contaminated with the weed. You can either dispose of them, or manually remove the rhizomes and quarantine them in pots for the season to ensure their soil is weed-free. Unfortunately this technique will also negatively impact beneficial insects living in in the soil and for that reason we use this method selectively.
3 Frequent Mowing
Depending on the area affected, weed whacking or mowing can be an effective control of goutweed’s spread as it decreases the plant’s ability to photosynthesize. If thoroughly and persistently carried out weekly, this method will eventually weaken and kill the weed, but it will take much persistence and perhaps years to achieve the desired result.
4 Heavy Mulching
We’re not huge fans of this method as a stand-along solution but some have found success with it. Proponents of this approach advise mowing the weeds close to the ground and then putting down approximately a foot of mulch on top of the affected area (and, of course, a foot around all visible signs of growth). The reasoning is that the plant’s leaves and root system will migrate towards the light and be much simpler to extract from the loose mulch. With continuous extraction, the weed should be able to be eliminated over several seasons.
Finally, because goutweed is notorious for creeping through boundary lines, chances are that if you have goutweed, your neighbour does too. The best way to keep goutweed out of your yard is to trench. We’ve had success creating a 12 inch wide by 12 inch deep ditch along the property’s perimeter. First we dig, then we line with geotextile landscaping fabric, and finally we fill with gravel. Once this is done, the travelling rhizomes from the neighbor’s yard can’t penetrate through the trench. Usually, we develop a landscape design that includes mulching over the trenched area as a part of the landscape.
Goatweed is on the list of invasive species for the Halifax Regional Municipality and it is the most common issue that we are contacted about by local homeowners.
Be sure to monitor your property for this tenacious weed looking for it in either of it's two colours - solid green or a varigated yellow and green leaf.
It may seem to go without saying, but as goutweed grows under even the most severe of conditions, do not dispose of it in your compost: it will contaminate your bin. It has been known to bloom five days after being pulled, so please dispose of it accordingly!
While it can be neighborly to share or accept divided perennials, it is also one of the most common ways that your property can be impacted by goutweed. Even if there is no sign of a goutweed leaf, its rhizomes or dormant seeds may be present in the soil...so beware!
If revenge is best served cold, why not try adding goutweed to your salads? It is used as a popular vegetable, and even prized for its medicinal properties by many cultures throughout the world.
For more fun facts, check out http://www.thisgardenisillegal.com/2006/05/virtues-of-bishops-weeds.html
And that’s it folks. We’d love to hear your experience with this tricky creeper, please feel free to reach out!