The Fine Line Between Invasive and Enthusiastic
I grow several plants in my zone 6 garden that are considered “invasive” or plants that tend to spread rampantly. If you look on your State’s website, you will find a list of invasive trees and plants that should never be planted in your area. Purple Loosestrife, for example, is an aggressive grower in New England that is taking over marshes and ponds, choking out wildlife habitat. I’m not talking about the plants that have been blacklisted but instead the ones you can purchase from your local garden center that are best described as “enthusiastic” growers. Over the years I’ve discovered there’s a fine line between plants that are considered garden thugs and those that are helpful heroes. It’s all in how you use them.
Using Groundcovers
Many groundcovers are aggressive spreaders. As the name implies, these are generally plants that will cover a lot of ground and do it quickly! Groundcovers can be extremely valuable in covering unsightly areas of our yards where other plants won’t grow. For this reason landscapers love them but new gardeners may hesitate to bring these rowdy boys home. The trick with using assertive spreaders is to keep them from getting out-of-bounds.
A case in point is the innocent looking “Creeping Jenny” with its diminutive chartreuse leaves. Planted in rich garden soil, this bright gem spreads like a bad case of poison ivy and can easily take over your flower bed. I know this from personal experience! But I love the bright green color and delicate appearance of this plant, so I use it where it can be left to its own devices – in semi-shaded bare spots around the yard or combined with other plants in flower pots where its rampant growth is confined. In the right spot “Jenny” may even reward you with bright yellow summer flowers.
Another popular groundcover is Ajuga or Bugleweed. The common Ajuga reptans brightens my yard with beautiful blue or white flower spikes in May. It tends to spread into the lawn but, dug up and replanted in early spring, you can easily direct this plant where you want it to grow. Ajuga appreciates semi-shade but will adapt to full sun given adequate moisture. Two varieties that I love are “Black Scallop” and “Chocolate Chip” whose striking foliage looks good all season. (See photos below) Deep blue flower spikes are a bonus in the spring. Although Ajuga spreads quickly, it plays well with others in my garden beds and is easily divided and moved to other areas.
A native groundcover that I’ve used extensively in my yard is Vinca minor, also known as “Periwinkle” or “Creeping Myrtle.” In April, the glossy dark green foliage is covered with light blue flowers that positively sparkle in the sun. Vinca thrives along the bright edges of the woods and quickly covers large areas. On the aggressive side with its long runners attaching to any bare soil, this groundcover is best left to its own space where it will fill in to form a lush green carpet. One stunning early spring combination is the twinkling blue flowers of Vinca planted at the feet of bright yellow Forsythia!
Giving the Big Boys Room
Although we don’t usually think of our tall perennials as invasive, there are some big boys that tend to spread aggressively and quickly. Large clumps of sun-loving Shasta daisies, tall daylilies, phlox and perovskia can become almost shrub-like in size, easily overcoming a small garden. Tall grasses also make a big statement and need lots of space to spread. If you love big plants, give them plenty of room at the back of the border where they won’t dwarf your smaller perennials OR group them in a bed by themselves.
In the semi-shade garden, Grape Leaf Anemone is another back-of-the-border plant that can quickly grow to three feet tall and wide, and the long flower stalks may need support. Valuable as a prodigious late summer to early fall bloomer, the pale pink to mauve blooms blend beautifully with late-blooming hostas and Rudbeckia. Because of its robust constitution, it may need to be thinned out in early spring to keep it from taking over but it’s worth the extra effort just to enjoy the spectacular late season show!
Go Ahead and Grow It Anyway
The only way we learn about the nature of plants is to grow them ourselves. Remember that whatever a plant’s reputation, your experience with it will be unique to your climate and growing conditions. Don’t be afraid to try a plant with an eager temperament; just plant with restraint if using in established flower beds and monitor its habit over the growing season. Alternatively, if you want to cover a shabby area and turn it into something you’re proud of, using these vigorous spreaders can give you almost instant gratification. So, go ahead and take a few of these plants home for a test drive. Only then will you discover who are the garden thugs and who are the helpful heroes in your garden!
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