Spirea

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Spirea ‘Anthony Waterer’ (Spiraea japonica)

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While we’re talking about reliable plants, Spirea shrubs are a candidate for this class.

The old shrub ‘Anthony Waterer’ came with our house. Over the years, a locust tree grew to provide dappled shade.

‘Anthony Waterer’ grows as a rounded mound about 3 feet high and wide. The leaves are dark green with white or variegated sports thrown in here and there. (The golden or yellow cultivars like ‘Lemon Princess’ are brilliant against darker shrubs or evergreens.)

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That said, the plant comes with a warning -

According to the Pennsylvania Department of Conservation and Natural Resources list of invasive plants in Pennsylvania, Japanese Spiraea is “Frequently planted; escaped in some areas.”

”ECOLOGICAL THREAT: Japanese spiraea can rapidly take over disturbed areas.

“BIOLOGY & SPREAD: A single Japanese spiraea plant produces hundreds of small seeds that are naturally dispersed by water and deposited along stream banks. Seeds may also be carried in fill dirt and establish new populations in the highly disturbed soil of construction sites.

“Spirea has cultivars that are not known to be invasive. . . . If you choose to plant a cultivar of an invasive species, ask a PA certified horticulturist (PCH), your Penn State extension agent, or a professional horticulturist about the cultivar's potential to be invasive.”

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I make sure to dead head the shrub to remove the seeds. It was trimmed back to about 8 inches in the middle of March. When blooms begin to fade, I’ll use a hedge clipper to cut it back. It will bloom again and the blooms will continue into fall. Then I’ll give it another haircut. I haven’t heard any reports of Japanese spirea becoming invasive in our area.

Perhaps it’s the reliability of this plant that is also it’s curse.

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(More information on spirea from Clemson University Extension.) http://www.gardening-tools-direct.co.uk/content/spirea.pdf

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Invasive Plants

Two popular shrubs have become invasive in Pennsylvania dominating natural resources and depleting cover and food for wildlife – Japanese Barberry and Burning Bush.

Japanese Barberry (Berberis thunbergii) has never been a favorite of mine because of its sharp edges. It has a burgundy color that adds interest to the landscape so it is has become an attractive addition to many gardens.

According to Invasive Organization http://www.invasive.org/eastern/midatlantic/beth.html

“In the United States, Japanese barberry occurs throughout much of New England and the Northeast, south to North Carolina and west to Michigan and Missouri. Barberry forms dense stands in a variety of habitats, including closed canopy forests and open woodlands, wetlands, pastures, meadows and wastelands. This highly shade-tolerant exotic shrub displaces a variety of native herb and shrub species in areas where it is well established.”

The Barberry variety ‘Concord’ can be substituted providing everything the invasive plant offers without the seeds that promote invasiveness.

I do have personal experience with Burning Bush (Euonymus alatus). Purchased in the early 90’s, I wanted a shrub that would add some color to the fall landscape. I got the color but I also got hundreds of seedlings after the shrub matured. I’ve removed the bush.

The Global Invasive Species Team http://tncweeds.ucdavis.edu/alert/alrteuon.html has this to say about Burning Bush:

“This new invader is becoming increasingly common in Connecticut, Virginia, Pennsylvania, and Illinois. It has been observed making dense thickets in Pennsylvania. These thickets can shade out native herbs and crowd out native shrubs.”

Some native plant substitutes for Burning Bush worth checking include: maple-leaf viburnum (Viburnum acerifolium), Korean spice viburnum (Viburnum carlesii), service berry (Amelanchier arborea), spicebush (Lindera benzoin), strawberry bush (Euonymus americanus) or red chokeberry 'Brilliantissima' (Aronia arbutifolia 'Brilliantissima').

Even the much loved Butterfly Bush (Buddleia) has become invasive in some parts of the country. Since seeds of the Butterfly Bush don’t mature until spring, trimming spent flowers in the fall will greatly reduce the threat.

It may take a bit of research to make the right choice when buying shrubs or working with a landscaper. But, by staying away from the shrubs that can become invasive, at least I won't add to the problem.