Jul 10, 2018

Autumn Olive

Beautiful, but invasive, plant presents various threats to the ecological community

By Lawanda Jungwirth

I like to know the names of all the plants I see regularly on my daily walk. Not being able to identify something gives me the same uncomfortable feeling I get when I see words written in a foreign language. Just a little lost and ill at ease.

One morning last summer, I noticed a very pretty shrub I had never spotted before. I was immediately enamored of it. I loved the silvery, wavy-edged leaves. There was something about the way the leaves were arranged along the stems that pleased my eye. A few weeks later, I noticed the shrub had developed creamy yellow flowers, and in late summer, it produced beautiful red silver-speckled berries that looked like Christmas decorations.

After the berries developed, I noticed there was more than just that one shrub. In fact, there were a lot more. As soon as I realized just how many there were, I got a dreadful feeling that this handsome thing was invasive. I really didn’t want it to be a bad guy. I knew it was past time to put a name to the pretty face, and I started right off by searching the Wisconsin Department of Natural Resource’s list of invasive plants. Bingo. Only nine down from the top of the alphabetical list, and I knew it wasn’t one of the first eight. It was autumn olive. And once I had a name for it, I noticed even more of them along the trail!

Autumn olives leaves are dark green on top and silvery-white underneath. In late spring, fragrant, cream to yellow, half-inch trumpet-shaped flowers bloom in the leaf axils, followed by the slightly egg-shaped silver-speckled red berries I so liked. The shrub grows 10 to 20 feet tall and is usually a bit taller than it is wide. Young stems are speckled silvery or golden brown and sometimes have thorns. Older stems are light gray to brownish in color.

 

Sub: The threat?

So what’s so bad about autumn olive? It creates heavy shade thus making conditions unfavorable for native plants that need direct sunlight. Its roots add nitrogen to the soil, making conditions even more unfavorable for native plants which generally prefer infertile soils. In addition, high nitrogen conditions promote the growth of weedy non-natives. When autumn olive grows along streambanks, it can increase stream water nitrate concentrations.

Many birds and animals eat the fruits of autumn olive including thrushes, cardinals, cedar waxwings, evening grosbeaks, sparrows, bobwhite, ruffed grouse, ring-necked pheasants, wild turkeys, mallards, raccoons, skunks, opossums and bears. It also provides nesting habitat for many songbirds and protective cover for upland gamebirds and rabbits. However … the bad far outweighs the good, and there are many native plants that provide the same ecological services without upsetting the delicate balance of the ecological community. Several alternatives to autumn olive are listed below.

Autumn olive spreads rapidly due to prolific fruiting – like 200,000 seeds per year from one shrub – followed by birds dispersing the seed like crazy. “Birds dispersing the seed” is code for “birds eating the fruits and pooping them out elsewhere undigested.”

Autumn olive thrives in just about any soil and is drought tolerant, so it’s found in open woodlands, savannas, forest edges, abandoned fields, fence rows, meadows, prairies, pastures, trail sides and roadsides.

How did this happen? Well, way back in the 1830s we began importing plants into the United States from all over the world. Autumn olive is just one of a large number of those imports that we’ve lived to regret. It was initially planted in the United States to re-vegetate disturbed areas such as mine spoils and as recently as the 1960s to beautify highways, act as windbreaks, and to control erosion. It was also sold commercially to beautify landscapes and gardens. Today it has spread from Maine south to Virginia and over the entire eastern half of the United States.

 

Sub: Taking control

Unfortunately, autumn olive is almost impossible to control once it is well established. Wouldn’t you know that trying to control it by cutting, burning and mowing only encourages prolific regrowth! As soon as it is identified, young seedlings should be pulled from the ground when the soil is moist enough that the roots will pull without breaking. Larger plants can be removed with a weed wrench. Make sure the roots dry out entirely so they don’t reroot or dispose of them in sturdy plastic bags destined for the landfill. The main thing is to prevent the plant from fruiting.

Normally I am against chemical control, but a large infestation of autumn olive can’t be controlled any other way. The Wisconsin DNR recommends the following:

“Treat foliage, cut surface, or girdled stem with glyphosate, triclopyr ester, or metsulfuron methyl with a surfactant. Basal bark application of triclopyr ester can also be effective. Treat foliage with a liquid spray during the active growing season. For cut stump or girdled bark treatment, use liquid herbicide by painting, dripping, or sponging onto surface. Consult an agricultural extension agent or a natural resource specialist for more information on these control methods.”

Please, please read the labels of whatever pesticide you choose, follow directions precisely, dress properly, and be careful!

The only effective non-chemical method of controlling autumn olive is by using goats. If you don’t have your own goats, you can actually rent them to bring in to clear an area of vegetation. They will debark the shrubs and will get up on their hind legs to defoliate branches up to five feet from the ground.

Spring and early summer are the best times to use goats for autumn olive control. They may clear an area in a single season, but they need to be brought back several years in a row to actually kill the plants. It is important to manage the goats so that they don’t overgraze the area of grasses and forbs which can lead to erosion and reduced diversity.

No matter which control method you use, you must monitor the site every few months for several years to make sure that autumn olive hasn’t re-sprouted from cut stumps or root pieces left in the ground. Yes, it’s a lot of work, but this is a bad one that could devastate our natural areas as badly as buckthorn has if we are not vigilant.

 

Lawanda Jungwirth

Lawanda Jungwirth grew up in Omro, Wisconsin and lives along the Fox River at Rivermoor with her husband, Ron. She has been a University of Wisconsin-Extension Master Gardener since 1994 and writes a gardening column for the Oshkosh Northwestern. She is interested in environmental issues, organic gardening, control of invasive plants, natural health and quilting. Email ljungwirth@charter.net.