Managing Knotweed Organically

Modern folk tales abound in Nova Scotia about the indestructible plant that grows like a weed all over our shorelines, dominating other plants with its giant bamboo-like stalks. I’m talking about Japanese knotweed, which is a problematic invasive plant across the province and beyond.  Japanese knotweed was once a prized garden plant, which is how it arrived on our shorelines. Over time, it became less popular because of its invasive quality. There is also some evidence that Japanese knotweed has hybridized with giant knotweed in Nova Scotia, making it an even more formidable foe. Knotweed is a pioneer plant that thrives in disturbed areas. It loves water and roots, spreading along shorelines and wet areas via floating root clumps. The main concern with knotweed is that is creates a monoculture by out-competing all other plants. This monoculture worsens shoreline erosion, decreasing biodiversity and creating an unsightly brown view throughout much of the year. Read more about Japanese knotweed in Nova Scotia here.

Japanese knotweed

Many a gardener has tried to tackle this plant, only to find it re-sprouts seemingly larger than before. Some have resorted to pesticides, which only further deteriorate our shoreline ecosystems. At Earthshine Gardens, we have been experimenting with organic knotweed eradication and have found our method to be extremely effective; having created diverse and beautiful shoreline gardens in what only a few years ago were knotweed monoculture jungles.  Our method is simple and achievable, using the following steps:

1.       Cut all the stalks and leaves off of the knotweed, prior to flowering if possible. The non-flowering aerial plant parts can be used to build biomass in the area and will not re-sprout if there are no roots attached.  The green plant parts can be laid down in the area to decompose, providing valuable nitrogen to build the soil as a foundation for other plants.

2.       Dig or cut out as many of the root clumps (called rhizomes) as you can. This is the main way that the plant reproduces. These are very hard and will take some muscle to uproot.

3.       Bag all rhizomes and seed heads in black garbage bags for disposal, to ensure they don’t sprout elsewhere.

4.       Lay a thick tarp over the entire knotweed area and weight it down well. The tarp will deprive the rhizomes of light and water, which will cause them to come closer to the surface over time so you can dig them out.

5.       Lift the tarp once per month for 1-2 years to remove any green sprouts and dig out rhizomes, using the same process as above. Over time, you will see less rhizomes, and eventually none at all. Walking on the tarp once per week or so will ensure shoots break and the tarp is not damaged.

6.       Create a sheet mulch over the entire area using thick cardboard topped by brush materials, compost, soil, woodchips etc. This will allow new soil to be created for plants to establish.

7.       Plant hardy perennials or shrubs over the area. Ensure that you use a diversity of different plants that are strong competitors but allow diversity. Add 2-3 inches of straw or bark mulch over top of the area.

8.       Keep an eye out for knotweed re-sprouting and pull it as soon as possible. If possible, work with other natural plants that are establishing in your new garden. This will allow a diverse, low-maintenance ecosystem to develop in your new garden.

I recommend folks try this method and let us know how it goes.  If you need help, we’re here for you. Just call Earthshine Gardens, the South Shore’s holistic ecological land care team.

Contact us to book your complementary site-visit today.

Spring Clean-Up for your Gardens

            South Shore gardeners know well the challenges of this wet, grey season. Our gardens can be rather uninspiring at this time of year – often brown and mucky rather than green and lush. But don’t let the drab exterior fool you! Soil life is at work and your plants are waiting for spring to shoot up and greet the warm sun.

            Early spring is the perfect time to get out into your garden and reconnect with the land. This work is important for our gardens and for us! We need fresh air, sunshine and the smell of soil to energize us for the growing season ahead. Read more about the benefits of nature for health and happiness here.

Caitlin works with volunteers to prepare a  mandala garden  for spring planting   (Sage Rising, 2014).

Caitlin works with volunteers to prepare a mandala garden for spring planting (Sage Rising, 2014).

Not sure where to start? I’ve got you covered. Here are my top five early spring garden clean-up tasks:

1.      Prune trees and shrubs. It’s best to prune large trees and shrubs during winter, before they break dormancy. In winter, sap descends to plant roots, reducing injury when we prune. Spring is also a good time to support any plants that were damaged in winter storms. The exception is any tree or shrub that flowers in early spring. For these wait until fall or until after they flower.

2.   Work the soil and warm the soil. When gardening, I aim to disturb the soil as little as possible. This allows soil life to develop and maintains the soil structure and horizon. Sometimes, though, we need to turn our gardens for planting, aeration and weeding. Early spring is the best time to do these jobs, because soil life is primarily dormant until the growing season begins. This is also a good time to pull back mulch from your spring plants and annual beds to warm the soil, encouraging growth and establishment.

3.   Clean up last year’s herbaceous plant growth.  I choose to leave most dead plant matter in my garden over winter. I do this because it insulates the soil and soil life, protecting it from erosion and winter weather. Some plants, like grasses, still look nice throughout the winter, and should be cut to the ground in early spring to promote new growth (read more about caring for ornamental grasses here). Now is the time to clean-up that dead matter, composting what you can to add fertility to your garden later (learn composting basics here).

4.   Plant cold-hardy annuals and cover crops. What can you plant at this time of year you ask? Cold-hardy greens and herbs of course! Try parsley, cilantro, kale, spinach, mustards and lettuces. This is also a great time to sow a cover crop to precede a summer crop, adding fertility to the garden and attracting insect pollinators (learn more about pollinator-friendly gardening here). Pea-oat mix and buckwheat are good options. Simply broadcast them and dig them in a few weeks before you plant your next crop.

5.   Clean and fill bird-feeders to attract birds, and their pollination services.  No garden is complete without bird friends! Remember to clean and dry your feeders to prevent spread of disease. Birds offer pollination and fertilization services while adding beauty and complexity to our gardens. Food is in short supply in early spring, when birds are nesting and need energy. Try adding more bird feeders. The birds will repay you with lushness for your garden and food for your soul.

If you need help with spring clean-up or any other garden and land care tasks, Earthshine Gardens is here to help. Jump start your 2018 landscape today with the South Shore’s holistic ecological land care company. Contact us today.

That said, nature awaits. Let’s get outside and garden!