The Block Island Times

A look at invasive plants on the island

By Fred Nelson | Sep 01, 2011

It is difficult to determine whether this summer is different from our normal summers unless one keeps copious records, such as true horticulturists who record daily temperatures, rainfall, sunshine, etc. By recording this information, they then may compare production from each of their crops.

Fortunately, I do not fit this category — what will be, will be for me. As I have mentioned in past articles, I have had a less-than-enviable garden this year. If it wasn’t too wet or cold, it was too windy — then it was too hot. Anyway, we have had sufficient produce to satisfy our needs, and what excesses we have had I have enjoyed sharing with different folks around the island. I really am already looking forward to a new and more fruitful season next year.

While we receive several gardening catalogs each year, I generally just leaf through them since I seldom purchase anything from catalogs. However, Muriel was reviewing a catalog and mentioned that most vegetable and flower seeds are now sold by the number of seeds. For instance, the Burpee catalog lists Wave petunia seed as $5.25 for 15 seeds (.$40/seed). With cost such as this, they must be pretty careful how they handle their seeds. Snapdragons varied anywhere from 50 seeds for $4.95 to 500 seeds for $3.95, depending upon the variety. Likewise, vegetables are also sold by the seed count.

I thought that this was an interesting change in the marketing of seeds. Imagine the technology that must be used to count seeds to insert them into a package. Perhaps instead of purchasing gold, one might want to consider petunia seed.

I have noticed that I have never had any preponderance of Japanese beetles — no more than I could easily count and usually on the asparagus. This year all I came across was one beetle. This would be good news since the beetles’ biggest menace is the larval stage, when they can cause extensive damage to lawns by chewing off the root system, thus killing the grass. Some other beetles who also have a larval stage can also cause the same damage as the Japanese beetle. Unfortunately, I have not taken the time to have the larva identified.

With the recent attention to the invasion of the mile-a-minute weed, this has brought to mind the number of invasive plants that we are endowed with here on the island. By my count we have at least 11 that have the characteristic to envelope or crowd out native plant life, including trees, which can result in the loss of many desirable native or cultured plants.

While grapes may have been indigenous to the island, it is as aggressive as any of the other invasive species. There are many areas that have been completely covered by the grape vines as they climb up to and over all sorts of plant life. Effective control is best achieved by vigorous and constant cutting back. For those in the craft business, here is an abundant supply of vines with which to make all sorts of decorations. If one is to pursue this hobby, be sure to ask permission from the landowner before harvesting any vines. The best time to cut would be after the leaves have fallen off.

Some of the other invasive plants include:

· Japanese knotweed (Polygonum cuspidatum): This plant is seen gracing our roadsides throughout the island; It is very difficult to control. Persistent, repeat cutting and herbicide use along with cultivation can bring results.

· Virginia (Parthenocissus quinquefolia): A vine that uses tendrils to climb plants, telephone poles and buildings (ivy-clad college campuses). While it spreads by the vine growth, the seeds are dispersed by the birds, thus starting plants wherever the seeds are dropped. Young plants are easily pulled out by the roots.

· Black swallow-wort (Cynanchum lousieae): This is another perennial, twining herbaceous vine. This plant develops into extensive dense patches of growth, crowding out other vegetative growth. This is spread by rhizomes and seed dispersal. This plant can also be seen starting to invade our roadsides and “open” land. Even small plants are difficult to pull out by the roots. Judicious use of the herbicide glyphosphate (Roundup) can confine this with time.

· One ornamental that you might associate as an invasive is the Butterfly bush (Buddleia davidii). I have had numerous seedlings germinate from our plants. At the corner of Center and Old Town roads, on the southeast corner, is an example of what can develop on untended property. Control simply by pulling out young plants.

I shall continue reviewing other notable invasives in a future column.

“Gardening is ... an outlet for frustration violence, love and rationality without their worst side effects.”

—Geoffrey Charlesworth

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