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Monday, May 1, 2017

Paradigm shift for pots

In response to my question about which perennials to use as fillers in containers, Patricia McGinnis, an astute reader, wrote suggesting that bigroot geranium (Geranium macrorrhizum) would be a good choice. As she points out, it has attractive multi-lobed leaves that turn red in fall, and it spreads moderately.

Bigroot geranium this week

  Patricia’s email opened my eyes, and now I’m spotting any number of perennials I can use in containers to replace the impatiens and coleus I’ve been buying for years. The impetus for this search is to avoid nursery plants that have been sprayed with pollinator-lethal “neonics,” neonicotinoid insecticides that persist in plant tissues.

No point in attracting insects and then poisoning them

     In case you’re not familiar with the expression, “fillers” refers to a popular dictum for container designs: include “thrillers, fillers, and spillers.” Tender perennials with big bold leaves are my usual thrillers, and I like to balance them with mid-sized fillers. 

Canna with calibrocha filler last July. Lobelia had already melted in the heat.

Ideally I include something that blooms for a long season, but distinctive leaf shapes, colors or textures work too.

     Just about any vigorous perennial of low to moderate height could be a candidate, I see now. If a plant is spreading, I won’t feel bad about digging up a few rooted sections to use in pots. Some perennial clumps are due for dividing. That will be an opportunity to use a piece in a container. If a plant’s showing aggressive tendencies, that’s all the more reason to wrench some out, pop it into a pot, and let it die at the end of the season.

     In the moderately spreading category, I can picture using wild ginger (Asarum canadense), which has large matte green leaves that stay fresh-looking all summer. 

Wild ginger stays elegant through the summer

I could also use its imported cousin European ginger (Asarum europaeum). The shiny round subtly variegated leaves of this groundcover captivated me back when I started my garden. After very slowly increasing for 30 years, it’s starting to pop up in unexpected places, and I have enough to spare for potting. Maybe I could replant it in fall after a sojourn in a summer container.

European ginger this week

     Some hostas and hellebores that I planted too close to shrubs are now looking crowded and unhappy. They could provide some chunky mass to balance the giant leaves of cannas and elephant ears in pots.

A mature hellebore can be quite bulky

     As for groundcovers with invasive predilections, golden creeping Jenny (Lysimachia nummularia ‘Aurea’) is expanding wildly. Its near-yellow color could provide an interesting contrast, and it might drop stems gracefully over the side of a container.

Golden creeping jenny: don't be fooled, there's no stopping it.

     People often stick something with thin, strap-like leaves, such as a cordyline or an ornamental grass, in the center of a pot as a vertical element. 

Cordyline for verticality--photo by Daryl Mitchell

Perhaps I could draft smooth Solomon’s seal (Polygonatum biflorum) for this role. It too has taken over a lot of real estate in shady sections of my garden.

Two species of Solomon's seal sending up their shoots

     I can’t wait to try some of these ideas when I fill my containers in May. I bet I’ll see more options as perennials continue to emerge in the interim. Thanks, Patricia!

Ah, April! Yellow trout lily (Erythonium americanum)

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