Pilchuck Pollinator

Recently there have been several new introductions of Periwinkle varieties that have pretty, small, variegated leaves that are used for foliage interest in baskets and containers.  As long as these varieties are kept confined, they are nice plants.  Dispose of plants in garbage rather than compost unless you have ideal compost conditions where the pile gets hot enough to kill all plant remains.

 

While most introduced plants are not considered as serious threats to native habitats, all plants that can self-sow easily should be monitored to make sure they don’t spread.  For example, the Foxglove (digitalis purpurea) is now found throughout so much of the NW that many people think it is a native species.  While not as aggressive in our meadows as some other introduced species, Foxgloves, which are native to Eurasia, are spreading.  This biennial plant produces copious amounts of viable seeds.  Foxgloves adapt well to open, sunny areas and compete reasonably well with many local species.  If your are growing them, deadheading fading flowers will help keep them under control.

 

Another example of a plant that needs careful deadheading is Common Lady’s Mantle (alchemilla mollis), It is much loved by flower arrangers due to its sprays of tiny chartreuse green flowers that are excellent fillers in floral arrangements.  However if let go, Lady’s Mantle can self-sow, and the seemingly indestructible seedlings come up everywhere.  There are many other plants that self-sow, for example, California Poppy (eschscholzia californica), Love In a Mist (nigella damascens), Yarrow (achillea ssp) and Verbena (verbena bonariensis).  I haven’t deliberately planted any of these species in my own garden for many years, but I find seedlings of these still coming up every spring.  They are all quite pretty, but they could easily spread if I didn’t keep them in check.

There are other plants which are becoming notorious for their ability to invade.  One of the worst is Chameleon Plant (houttuynia cordata), a pretty variegated herbaceous plant introduced into North American commercial horticulture about 20 years ago.  New Zealanders can’t believe we allow it to be sold as this plant has become a noxious weed in New Zealand where it has spread in their wetlands, much as Purple Loosestrife has spread here.  They are trying to completely eradicate it before it becomes an even more serious problem.  Himalayan Balsam (impatiens glandulifera) is another plant that is well adapted to wet sites and grows so thickly that it chokes out everything else.  In eastern Canada, there are concerns about the spread of Norway Maple (acer platanoides) and Amur River Maple (acer ginnala).  To date, they are not considered as serious threats to forests, but we may hear more about their spread in the future. 

 

If you do decide to grow any potentially invasive plants, take the responsibility to make sure they don’t spread beyond your own desired growing area.  Deadhead plants as soon as the flowers are spent.  Learn to recognize seedlings of self-sowing plants so they can be removed when small.  Plants like English Ivy and Periwinkle are useful, but consider confining them to containers or beds where they aren’t likely to escape.  When weeding these or cutting back, don’t put pieces into a compost pile since they might accidentally be moved around the garden when spreading compost.  Never dump the contents of old planters into the wild, as this is one of the major ways plants are introduced into our native habitats.