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RAVENNA GRASS A NOXIOUS WEED ESCAPEE FROM GARDENS

GARDEN TIPS – written by Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Written August 6, 2015

RAVENNA GRASS A NOXIOUS WEED ESCAPEE FROM GARDENS

Most gardeners I know are concerned about the environment and would be upset to learn that about half noxious weeds in this country were introduced by gardeners like themselves. Gardeners are always excited to find an interesting or unique new plant for their yards and gardens. Unfortunately, some of these plants escape the confines of the garden and wreak havoc on wildlife habitat and agricultural lands.

One of these escapees is Ravenna grass (Saccharum ravennae), a large “ornamental” grass, also called “hardy pampas grass” or “plume grass.” It is so named for its resemblance to pampas grass, forming large 3 to 4 feet diameter clumps and producing 12 feet tall flowering stems topped by attractive silver feathery plumes. Unfortunately, the plumes produce plenty of minute seeds that are easily in spread wind and water.

Ravenna grass proliferates in gardens, irrigation drainage ditches, wetlands, and riparian areas where it can crowd out habitat, create impenetrable areas, and restrict stream flow. It could become a problem in eastern Washington along the Columbia and Yakima rivers and is already a serious problem in many other western states.

Where did it come from? Ravenna grass is native to the Mediterranean region and has been sold by the horticulture industry since about 1921 as a desirable ornamental grass. In fact, a quick search of the internet indicates that you can still buy it. Fine Gardening magazine touts its height as a striking vertical accent for the landscape and notes that it is deer, drought, and frost tolerant. Nevertheless, do not to buy it or plant it. It will spread via the seeds and become a weed problem in your yard, your neighbors’ yards, and beyond.

Our local Master Gardeners unsuspectingly planted some Ravenna grass several years ago in the Ornamental Grass garden of their Master Gardener Demonstration Garden. It thrived and spread itself throughout the entire garden and the neighboring library landscape. They were clued into this invasive grass by a local noxious weed board employee who advised seeking out all the plants in the garden and digging them out. (Ravenna grass is classified as a Class A noxious weed by the Noxious Weed Board of Washington, requiring all of us to remove it from our land.)

Before they could attack the Ravenna grass infestation, the Master Gardeners needed to know its identifying characteristics. Without the flowers or seed heads, it is often hard to tell one ornamental grass from another. However, Ravenna grass leaves are distinctive with a white mid-vein running the length of the 0.5 to 1 inch wide and 3 to 4 feet long blades. The blades are blue-green in color with very hairy bases.

Once they knew what it looked like, the Master Gardeners were ready to attack the grass by digging it out the plants and their roots because that is the most effective method of control in gardens and landscapes. There are not yet recommended chemical control recommendations for controlling Ravenna grass in home gardens.

The Master Gardeners found and removed over 200 smaller plants not yet producing flowers and seed along with the offending larger plants originally planted in the Ornamental Grass garden and responsible for the problem. They averted a noxious weed disaster in their garden, but this grass was unknowingly bought and sold to many other gardeners in our state before nurseries were made aware of the problem. If you have “hardy pampas grass” in your landscape, check it out, and get digging if you find that it is Ravenna grass. For more information on Ravenna grass consult the Noxious Weed Control Board of Washington at: http://www.nwcb.wa.gov/detail.asp?weed=193

THE RUSSIAN-OLIVE TREE IS NOXIOUS

written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

At this time of year not very many people come to me with gardening problems. The most frequent questions I receive are those related to fall gardening chores. However, this time of year is also when I get some uncommon questions. This week one query was regarding the edibility of Russian-olive fruit. I suspected that they were edible, since I knew the fruit of the closely related “autumn-olive” bush was edible. However, it’s never a good idea to guess about edibility, so I checked to make sure. Yes indeed, Russian-olive fruit are edible.

Perhaps you’ve never noticed the fruit of a Russian-olive. It’s an oval, one-half inch long fruit that’s silvery gray to yellow. The fruit matures in late summer and has sweet tasting flesh. The trees typically produce lots of fruit that are eaten by birds and other wildlife. In fact, these animal foragers have helped spread what has become a noxious weed in many central and western U.S. states.

The Russian-olive (Elaeagnus angustifolia) is a shrubby tree that’s native to southern Europe and western and central Asia. It’s not a true “olive”. Like its cousin the autumn-olive, it’s a member of the Elaeagnaceae or oleaster family. It’s planned cultivation started in Germany in 1736. It was introduced into the U.S. in the late 1800

s as a desirable ornamental tree and as a good choice for a windbreak. It was hardy and thrived in many tough situations. The U.S. Soil Conservation Service sold it for many years and encouraged its use in windbreaks and wildlife plantings.

With its prolific production of fruit and with the help of wildlife, it didn’t take it long to become naturalized in the regions to which it was introduced. Because Russian-olive is a very adaptable plant, it has done well in many different situations, especially in riparian areas along streambanks and riverbanks, flood plains, and marshy areas. It will grow in almost any type of soil and can survive both extremely cold (-50 degrees F) and extremely hot (115 degrees F) temperatures. The Russian-olive is able to fix nitrogen with its roots, allowing it to grow in very poor soil where many other plants can’t survive without help.

The plant itself is usually a large multi-stemmed shrub or tree that grows to a height of 20 to 40 feet. Its thorny branches make it a particularly nasty plant. Some like the Russian-olive’s silvery or gray appearance, created by its silvery scale-covered twigs and the leaves which are gray green on top and covered with silvery scales beneath.

So why is the Russian-olive considered a noxious weed in many regions? After all, its planting was encouraged for many years because it thrives in poor soil and harsh climate conditions. Unfortunately, it thrives a little too well. It takes over in areas and competes much more successfully than native vegetation. This invasive shrub was once thought of as a good plant that provided food and cover for wildlife… and it does. However, research shows that more species of birds will inhabit areas where native vegetation dominates than where Russian-olive has taken over.

Another strike against the Russian-olive is the problem it causes allergy sufferers. The prolific flowers (which later turn into fruit) produce lots of pollen which is a common allergen for many individuals.

Yet another problem with Russian-olive is that once it’s established in an area, it’s almost impossible to eradicate. Part of the reason for its tenacity is its ability to easily regrow from sprouts that come up from the base of the trunk when the plant is cut down. Much study has gone into ways to control this non-native invader and some say that not much destroys it… short of using of explosives. However, there are some less drastic strategies to try.

Simply cutting the shrub or tree back to the ground won’t work, because sprouts form at the trunk and from the roots. This encourages thicker, more dense growth. Intentional burning or wildfire also results in this thicker regrowth. The best bet is to treat freshly cut stumps with brush-killer products containing glyphosate or triclopyr. The sprouts that regrow can also be treated with these brush-killing chemicals, but care must be taken not to get the chemicals on any desirable plants. Retreatment of regrowth is often necessary.

Russian-olive is considered a noxious weed in several western states, but it’s not currently listed on the Washington State Noxious Weed List. However, it is considered an invasive ornamental “bully” that should not be planted. Considering its thorns, pollen production, and invasiveness, it really isn’t a very friendly plant.

Footnote: As I mentioned, the fruit is edible and sweet, but I didn’t say they were tasty. The fruit is actually dry and mealy. However, I have eaten jelly made from the fruit of the autumn-olive, the Russian-olive’s cousin, and it was delicious.

Published: 11/26/2005 11:31 AM

The Russian Olive Tree Is Noxious

written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA

At this time of year not as many people come to me with gardening problems. The most frequent questions I receive are those related to fall gardening chores. However, this time of year is also when I get uncommon questions. This week one query was regarding the edibility of Russian-olive fruit. I suspected that they were edible, since I knew the fruit of the closely related ‘autumn olive’ bush was edible. However, it’s never a good idea to guess about edibility, so I checked into it to make sure. Yes indeed, Russian-olive fruit are edible.

Perhaps you’ve never noticed the fruit of a Russian-olive. It’s oval, one-half inch long fruit is silvery gray to yellow. The fruit matures in late summer and has sweet tasting flesh. The trees typically produce lots of fruit that are eaten by birds and wildlife. In fact, they help spread what has become a noxious weed in many parts of the central and western regions of the U.S.

The Russian-olive (Elaeagnus angustifolia) is a shrubby tree that has been declared a noxious weed in many areas. It is native to southern Europe and western and central Asia. It is not a true ‘olive’. Like its cousin the autumn olive, it’s a member of the Elaeagnaceae or oleaster family. It’s planned cultivation started in Germany in 1736. It was introduced into the U.S. in the late 1800

s as a desirable ornamental tree and as a good choice for a windbreak. It was hardy and thrived in many tough situations. The Soil Conservation Service sold it for many years and encouraged its use in windbreaks and wildlife plantings.

With its prolific production of fruit and with the help of wildlife, it didn’t take it long to become naturalized in the regions to which it was introduced. Because Russian-olive is a very adaptable plant, it has done well in many different situations, but especially in riparian areas along stream and riverbanks, flood plains, and marshy areas. It will grow in almost any type of soil and can survive both extremely cold (-50 degrees F) and extremely hot (115 degrees F) temperatures. The Russian olive is able to fix nitrogen with its roots, allowing them to grow in very poor soil where many other plants can’t survive without help.

The plant itself is usually a large multi-stemmed shrub or tree that grows to a height of 20 to 40 feet. Its thorny branches make it a particularly nasty plant. Some like the silvery or gray look Russian olive created by its silvery twigs and the leaves which are gray green on top and covered with silvery scales below.

So why is the Russian olive considered a noxious weed in many regions? After all, its planting was encouraged for many years because it thrives in harsh soil and climate conditions. Unfortunately, it thrives a little too well. It takes over in areas and competes much more successfully than native vegetation in many areas, taking over the moist areas where it grows best, such as river banks and irrigation canals. This invasive shrub was once thought of a good plant that provided food and cover for wildlife and it does. However, research shows that more species of birds will inhabit areas where native vegetation dominates than where Russian olive has taken over.

Another strike against the Russian olive is the problem it causes allergy sufferers. The prolific flowers (which later turn into fruit) produce lots of pollen which is a common allergen for many individuals.

Yet another problem with Russian olive is that once it’s established in an area, it is almost impossible to eradicate. Part of the reason for its tenacity is its ability to easily regrow from sprouts that come up from the base of the trunk when the shrub is cut down. Much study has gone into ways to control this non-native invader and some say that not much destroys it short of the use of explosives. However, there are some less drastic strategies to try.

Simply cutting the shrub or tree back to the ground won’t work, because sprouts form at the trunk and from the roots. This encourages thicker, more dense growth. Intentional burning or wildfire will also result in thicker regrowth. The best bet is to treat freshly cut stumps with glyphosate,, the main ingredient in Roundup, or triclopyr. Regrowth sprouts and leaves can also be treated with these brush killing chemicals, but care must be taken not to get the chemicals on any desirable plants. Retreatment of regrowth is often necessary.

Russian olive is considered a noxious weed in several western states, but it is not listed on the Washington State Noxious Weed List. However, is considered an invasive ornamental ‘bully’ that should not be planted. Considering its thorns, pollen production, and invasiveness, it really isn’t a very friendly plant and I would also advise against it.

Footnote: As I mentioned, the fruit is edible and sweet, but I didn’t say they were tasty. The fruit is actually dry and mealy. However, I have had jelly made from the fruit of the autumn olive, the Russian olive’s cousin, and it was a favorite of mine… when it comes to edible wild plants.

Published: 11/19/2005 11:32 AM

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