I bought perennial sweet peas in a garden centre in Toronto and planted them in my garden because they look pretty but after a couple of years they became very invasive and is destroying my other plants by climbing on them and overcrowding the area. What to do to get rid of them? I pull them manually wherever I see them but it’s not working because their roots are deep. Are these acid loving or alkaline loving plants? I don’t want to destroy my other plants. These should be included in your invasive species guide. Thanks for your advice.
Perennial sweet pea (Lathyrus latifolius) is a vigorous climbing perennial that’s native to Europe.
While it’s not classified as a priority invasive species in Southern Ontario, it’s an aggressive spreader (see the definition of invasive vs. aggressive here) because it spreads by rhizomes and by seed, making it doubly difficult to control. It is listed as an invasive species in many US states. It can grow in soils of all pH types, which is another reason why it’s so persistent.
In order to prevent its spread, you’ll need two strategies – 1) removing flower heads before it goes to seed and 2) digging out spreading rhizomes (rhizomes are underground stems that send out roots and shoots) – dig down until you get the whole rhizome and the roots. Just pulling out above ground stems won’t eradicate them.
Some great alternative climbing perennials with interesting flowers or leaves that are native to Ontario (and thus benefit native pollinators and birds) include the following:
- Virgin’s Bower (Clematis virginiana)
- Trumpet honeysuckle (Lonicera sempervirens)
- Virginia Creeper (Parthenocissus quinquefolia)
There are other native vine suggestions in the Grow Me Instead guide. Keep in mind though that all vines have evolved to spread – they are vines after all! So if you’re looking for something that is more contained, I’d suggest a shrub or herbaceous perennial for your location.