Jacqueline Houston is a member of the Wedgwood Garden Club, and also a Master Gardener of King County. She has been gardening in Seattle for over 30 years, and now has a garden consulting/coaching business called Enchanted Garden Consulting. Wedgwood Garden Club always welcomes new members – contact Jacqueline at tppoems@comcast.net for more information on our monthly meetings.
Every garden has microclimates within it – areas that are more sunny or shady, more damp or more dry – allowing for different plants to thrive in the variety of locations. But one thing I never read about, but have learned to value, is areas that are more alkaline (limey) than the rest of our mostly acidic soils.
Pacific NW garden soils run on the acidic side, hence our happy populations of rhodis, azaleas, camellias, western sword ferns etc, all of which like more acidic soil. But in areas next to concrete driveways, paths or pavers, or in planting beds edged with broken-concrete walls – my go-to free material! – certain plants that prefer a more alkaline environment will thrive.
I love pinks (dianthus), in particular the humble, low-growing ones such as cheddar pinks (see photo – sadly the recent rain removed all the petals) that tumble so picturesquely over a low retaining wall, and I have found that they like that trace of lime that leaches from concrete into adjacent planting areas, and do much better for it.
English wallflowers (Cheiranthus cheiri) also enjoy this kind of placement, not surprising when you realize their name derives from their common presence in old castle walls (that lime mortar!), where – tradition says – they were actively encouraged to grow so that their fragrance would waft through the castle windows.
And any plant that happily seeds itself in the cracks between pavers is already demonstrating a tolerance for the presence of lime – my white flowering mullein (Verbascum ‘Wedding candles’ – a bee magnet) has self-seeded in just this kind of spot 4 times in my front yard, slithering its long roots down through the merest crack between pavers and broken-concrete wall to form large mounds of foliage and flowers.
The reverse of this useful nugget of knowledge is to avoid planting acid-loving plants such as blueberries, too close to a lime-leaching environment. I recently advised a client to move her 3 unhappy blueberry bushes from a narrow bed between her house’s concrete foundation, and a paved patio, and I hope next year she will finally get a good crop of fruit at last.