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Botanical volunteers: the good and the bad

by Sue Schenk, Claremont Garden Club

Without being deliberately planted, “volunteers” appear in our gardens from seed released by plants we did intentionally introduce, blown in by the wind, spread in compost, buried by squirrels, sneaked in by neighbor’s vines that root along the ground, or dropped by one or the other ends of birds.

On the plus side, these are free plants and ones that are likely to do well in your garden conditions. They might not be ones you had considered planting but they can create interesting combinations of color and texture in your garden beds that you may not have thought of. They also provide you with gifts for friends!

A crape myrtle seedling appeared in my garden 25 years ago and now provides lovely pink flowers, good autumn color and interesting bark so I’m happy to have it. I also have several mature Japanese maples, the offspring of a neighbor’s tree. I must admit to being a fan of serendipity in the garden, so I generally wait until I know what something is before I pull it up.

What about the downsides? I’m happy with the honesty, cosmos and evening primroses that pop up every spring, but am going to have to be brutal to the sweet alyssum seedlings I noticed threatening to create a carpet that will compete with other plants. If you grew hybrids and want more of the same, then don’t let them seed.

Hybrids exhibit traits different from their true-breeding parents, but their offspring will exhibit a mix of traits, so if you want all the new ones to look like the originals you planted, you’ll need to buy new hybrids. On the other hand, if you’re okay with variety, let them go to seed and see what you get. Be aware, also, that unless all the plants of a particular open-pollinated species in your area are genetically identical, their seeds will produce offspring showing a range of qualities (just like human children do).

I had a loquat that volunteered and the fruit was terrible. If you want more of a particular rose, shrub or fruit tree, you need a clone. You can get these by rooting some cuttings or buying them from a nursery that rooted or grafted the desired variety.

So, are “volunteers” the same as those invasive plants that we are told to worry about? Well, some are and some aren’t. All plants evolved in response to conditions in a particular area. If they have the ability to spread so aggressively in areas outside of where they originated that they cause damage to their new environment (or to us), they are considered to be invasive. 

Kudzu was introduced from Japan in the 1800s as an ornamental vine and in the 1930s to help control erosion in the southeastern US, and it is a serious pest there where the conditions are right. The climate in Claremont isn’t right for it so it wouldn’t spread invasively here. 

Yellow star thistle, on the other hand, which appeared here accidentally from Eurasia in the mid-1800s, thrives in our Mediterranean climate and can be found throughout the city, although not usually in cultivated gardens. Each spring, the Bernard Field Station volunteers pull out masses of the plants which love the native coastal sage scrub habitat (to find out about volunteer days, go to bfs.claremont.edu).

Some plants that are not threats to local natural habitats can, however, be invasive in the garden. I foolishly planted some airplane plants, Chlorophytum comosum. Before I knew it, small plantlets on the ends of long stems rooted, leapfrogging and smothering whatever was next to them, and the thick, fleshy roots are hard to dig out.

If you want to discourage volunteers, be diligent about removing flowers before they go to seed, keep a thick layer of mulch around plants to make it more likely that seeds won’t reach the soil, and remove any volunteers that do show up early on to prevent them from ever reaching the seeding or other reproductive stage. But consider the fun of surprises before you pull them all up!

Please visit the Claremont Garden Club website at claremontgardenclub.org, which provides lots of help for gardeners. Also, find information about the March 23 and 24 Claremont Flower Show the Garden Club is sponsoring with the Woman’s Club of Claremont, and about purchasing tickets for the April 15 Claremont Garden Tour.