Steele: Some plants wear out their welcome
For the past six years I have been trying various plants in unwatered, sandy, partly sloping ground under a large Honey Locust tree.
I began with easy, self-seeding annuals such as Shirley poppies, alyssum, calendulas, marigolds, zinnias, cosmos, amaranth and sunflowers. Initially very successful, as the tree canopy got denser, fewer of these flourished.
As I have lots of perennials growing in my other gardens I moved in babies or pieces of plants that I thought would tolerate the conditions.
The outer edge of this garden is beside the road, gets more sun, plus reflected heat from the pavement, and is on city land.
While I was away visiting my son in Holland and enjoying the bulb gardens in 2009, the whole strip got dug up to replace underground cables.
That was a shock to come back to. I resolved to only use tough spreaders at the roadside.
Native white yarrow has self-seeded and I have encouraged it but am now removing some as other plants fill in. Giant lambs ears does well.
Seedlings from my thyme plant are thriving.
Another short shrubby perennial, Hyssop officionalis has seeded prolifically. Seedlings of both are easy to pull out.
Last year, I added in some clumps of Cerastium (Snow-in-Summer) and Artemesia ‘Silver King.’ Yesterday I spent a lot of time digging these out.
In one year they had invasively spread by roots into all adjoining plants.
In winter, the roadside garden has the additional challenge of being covered in salty, gravelly snow.
All of the above survived well, as do German iris, sedums, and Centranthus ruber (Jupiter’s Beard). When I first planted the shade garden at the front of the house, my sister brought me Lamium ‘Chequers,’ ‘Beacon Silver’ and ‘White Nancy’ all originally from our mother’s garden.
These served to brighten spaces with their variegated silvery foliage and summer-long pink or white blooms. They spread by roots and seed.
Suddenly this spring they are excessively abundant and overgrowing adjacent plants.
The cool wet weather is likely part of the reason. I have spent a lot of time digging out unwanted plants.
In my back garden, Tradescantia (spiderwort) has been beautiful for eight years. Suddenly it is seeding everywhere. It has a huge root system so takes time to remove when close to other plants.
It is not worth keeping when it causes so much extra work.
Mint and oregano are massive spreaders so I grow these in pots and don’t let them go to seed.
Lessons reinforced this spring:
To prevent extra work in the garden it is wise to avoid anything that spreads quickly by root or from small pieces broken from the mother plant (i.e. Sedum acre).
If babies from a self-seeding plant are not wanted, dead flowers need to be cut off before they go to seed.
Gwen Steele is executive director of the non-profit Okanagan Xeriscape Association. Learn more about Gardening with Nature and plants for the Okanagan on the website at www.okanaganxeriscape.org.