Beware of Some Pass-Along Plants

Bee balm (Monarda didyma) spreads fast and can be susceptible to powdery mildew. Photo: Lise Jenkins.

THE ABSENTEE GARDENERS

By Kit Flynn and Lise Jenkins

Last week I extolled the virtues of the Southern tradition of pass-along plants. Sometimes the only way to acquire a plant that is no longer at the height of fashion — yes, plants go in and out of fashion just like hemlines go up and down — is through the pass-along process. This is one way we can maintain plants of historic value, plants that are closer to the original species that existed before ultra-hybridization occurred. Old plants are part of our history.
 
However, there is a caveat: Many pass-along plants are extremely vigorous to the point that they are invasive — and invasive plants should have no place in our gardens.
 
Not all old plants make good pass-alongs. A pass-along plant has to be easy to propagate. For example, my Euscaphis japonica, the Korean Sweetheart Tree, produces many seeds, but the seeds must undergo an arduous process in order to germinate. Consequently, this tree, albeit a seedy one, is not a good pass-along plant candidate.
 
Years ago, when I was relatively new to gardening, a friend gave me some yellow flag irises. Irises are desirable, right? This geophyte travels speedily via rhizomes, producing rather insignificant yellow flowers along the way. It has little merit. Fortunately, I hadn’t planted it near shallow water and could easily pull it out. Plant it near water, however, and you’ll never be able to get rid of it. Instead, plant other irises, such as bearded, Japanese roof or Louisiana.
 
Generally, plants that are easily divided make acceptable pass-along plants. Plant daylilies, crinums, aspidistra and hostas to your heart’s content. Those that easily escape are the ones to be wary of. You wouldn’t plant kudzu, now, would you?
 
All this takes some investigation on your part. A simple Google search would have informed me that yellow flag irises were best kept out of my garden. The authors of the book Passalong Plants, recognizing that some plants are undesirable, have a chapter on “plants that get away.” These are plants you must not, under any circumstance, install in your garden. Alas, they typically have lovely flowers, delicious fragrance and are easy to grow.
 
An example is the trumpet vine, Campsis radicans. Its beautiful flowers entice hummingbirds. But plant it near the house, and it will pry off the shingles. It will grow anywhere there is sun or shade except, perhaps, in Death Valley.
 
Daylilies are safe, except for the species Hemerocallis fulva, the orange daylily you see growing along highways. Its tuberous roots travel, and the seeds spread. Our native bee balm, Monarda didyma, while easy to pull out, can be susceptible to powdery mildew. Most bee balms flop while filling out spaces in the garden. Hybridizers now have produced clumping bee balms that can be divided. Depending on your garden, these might be the better choice.
 
When I first saw Clematis paniculata, Sweet Autumn Clematis, I was overcome with lust. This is a dangerous clematis because (1) it’s beautiful; (2) it’s fragrant; and (3) it grows easily. Once planted, it will ensure that its seeds go everywhere — and you will never get rid of it. Beware of this plant as it’s sold everywhere.
 
A native wildflower to refrain from planting (although it’s widely available) is Tradescantia virginiana, Virginia spiderwort. As the authors state, “It’s a bad boy that can’t stay put.” An added disincentive is that it’s so deep rooted that it cannot be pulled out. If happiness is picking up a shovel, this is your plant.
 
The last plant I’ll mention is Cleome hassleriana, an annual that arrived from the West Indies. This could be a perfect annual, if it didn’t have small painful spines along its stem, a rather unpleasant aroma and seeds that remain vibrant in the soil throughout the winter.
 
In sum, as we noted last week, pass-along plants can be delightful additions to the garden. However, it’s mandatory to do your homework first. Otherwise, you could end up with a yard covered in kudzu. 


Absent from their gardens, Kit and Lise enjoy roaming our region exploring the intersection of horticulture and suburban living. More on Instagram @AbsenteeGardener or email: info@absentee-gardener.com

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