Yucca Removal Success

I took a little time to evaluate the success of my earlier efforts to eradicate Yucca from my fields.  Dead stumps where I had cut the stem and applied glyphosate to the exposed tissue.  This photo was taken in October, about six months after herbicide applications were made.  In most cases, there seemed to be a total kill of Yucca plants.

In a very few cases, there was some regrowth, but regrowth was not the normal situation.  It won’t take a lot of effort to go through to cut and spray the young shoots.  For the next few years an annual check will have to be made to find new plants growing from seed.  New plants will be a possibility for quite some time, but it should be fairly easy to keep the area practically Yucca free.

I only had time to cover about two-thirds of the Yucca infected area before I had to move on to higher priority management activities.  I finished my work in the open field and then began working my way down a cedar filled waterway.  This is where I stopped and this is where I will begin next March.  Weather permitting, I will have eliminated Yucca from the area by next April 1.

One thing I hadn’t expected was the ability of the cut plants to continue growing.  This is what my plant pile looked like after six months.

 

The Whitetail Deer treat it as a salad bar.  I never saw this much deer browse on the Yucca in the field.  Young Yucca shoots must be more palatable to the deer.

Pulling a shoot out of the pile reveals white roots growing from the cut stem.  This illustrates a good reason for removing the cut plants from the field as they are treated.  The Yucca may flourish in the pile for a couple of years, but I am always adding to these piles, so the plants will eventually be covered and smothered by other plant material.

 

Yucca Removal

Yucca, Yucca filamentosa, has slowly been encroaching on one of my prairie areas.  Yucca filamentosa is a North American native plant originally confined to the south-eastern portion of the United States.  It is considered to be a naturalized species in Ohio, with populations generally spreading from sites of human habitation where Yucca was planted for such uses as food, medicine or ornamental purposes.  Since I manage for native populations, the Yucca, non-native in my area, has always been on my list of plants to eradicate, but there have always been more serious matters for me to deal with.  A few years ago I began to notice new Yucca populations popping up hundreds of feet from the original infestation.  That discovery caused me to move Yucca removal to a higher level on my priority list.  After a couple of years testing treatment methods, I began in March 2020 to eliminate Yucca from Blue Jay Barrens on a large scale.

The long pointed leaves have fibrous strands that give the plant a rather worn look.  These are the filaments from which its scientific name derives.  The leaf edges can sometimes be abrasive and the leaf tips are often sharp.  I got plenty of scrapes and pinpoint wounds while dealing with this plant.

The vertical stem is generally quite short, but can sometimes reach up to a foot in height.  The leaves grow in a whorl from the stem with new growth coming from the tip.  The old leaves die to form a thick mulch that eliminates any competing plants from growing near the Yucca.

Here is the point of original infestation.  This open hilltop allowed for seeds to easily spread down hill.

I thought the origin site to be an excellent beginning point for Yucca eradication.  Especially since I have a well used walking trail running along the edge of this area and I was tired of seeing Yucca every time I went by.

From the top of the hill, Yucca spread down the slope to the west.

With this area cleared, I really had to stretch my neck to see any Yucca from the trail.

Yucca spread out near the base of the hill.  All cut Yucca plants were moved to a brush pile seen just to the right of the center of this photo.

At this point, all Yucca plants in the prairie area have been removed.  Those plants showing on the right side of the photo were removed the day after this picture was taken.

 As I cut off the Yucca plants, I piled the tops for future collection.

Cut plants were loaded onto a tarp and dragged out of the field.  Fortunately it was a down hill drag to the brush pile.

This pile, roughly six feet high and twelve feet wide, was made of plants cut from about one acre of prairie.  The pile will quickly shrink in size as the plants decompose.

Deer will generally not browse Yucca plants.  However, they seem to very much like the stems and treat the brush pile as a huge feeding station.  Individual plants are pulled out of the pile by the deer. They dine on the normally unreachable stem and leave the tops strewn about, sometimes a long distance from the pile.  Cut Yucca plants will easily root and continue growing if left on the ground, so I have to periodically gather up the tops and replace them on the brush pile.

I’ve removed Yucca from about one and a half acres of open prairie.  I still have about a half acre of Yucca growing in a shaded drainage area.  Other priorities have temporarily taken me away from this work, but I hope to continue the Yucca removal job later in the summer.  At a minimum, I will cut the flower stalks to eliminate seed production for this year.

A clump of mature Yucca plants appears to be a formidable adversary, but pushing aside the lower leaves reveals a soft underbelly.  Although the stems may reach a diameter of two inches, they are very soft.  I had no trouble slicing the stem with a pair of standard hand pruners, often severing the stem by simply pushing the pruner blade on through.

Removing the cut plant reveals the severed stems surrounded by a dead zone resulting from shading by the Yucca leaves.  In some of the larger clumps, lateral stems were poised to add to the size of the colony.  All parts of the stem in contact with the ground produce roots, so each new stem could become a standalone plant.  The roots are reddish in color and can be seen near the cut stems.

After cutting, I applied concentrated glyphosate, typically a 41% solution, to each cut stem.  Not knowing if the glyphosate would effectively eliminate the developing stems, I cut the tip from each young stem and treated it with glyphosate.  In my earlier trials, this method proved to be nearly 100% effective in killing the entire plant.

I treated a wide range of plant sizes.  Large plants were the easiest to find, cut and treat.  Smaller sized plants, such as that shown just below the large cut stem in the photo, were harder to locate.

Over the next few years I’m sure to be dealing with many small plants that evaded my search, but I’m sure the days of a widespread Yucca invasion are over. 

Yucca

Yucca filamentosa is the flower for people who like white blossoms. This thick bodied bloom looks as if it were sculpted in a confectioners kitchen. This is a six parted flower, as evidenced by the number of petals and stamens.

Yucca is a plant native to the south-east United States, so Blue Jay Barrens is not within his natural range. In one context it would be considered a non-native invasive species, because it will spread and take over an area. However, there are other more tolerable categories into which this plant might fit. One of those is the idea of Heritage Species. These are plants that have played an important role in the lives of our ancestors and because of that, have earned a special place in the landscape.

Yucca grows in dry sandy or rocky soils. The fact that the natural range of this species is not terribly far from southern Ohio suggests that it could easily have become one of our native species without out help. Some sources cite historical accounts of settlers carrying the Yucca along with them to plant in their new homesteads. Other sources talk about Native Americans growing Yucca near their settlements and moving it with them as they migrated. The Yucca at Blue Jay Barrens grows on top of the cleared hill. As far as I can discover, no one knows of any cabin or dwelling being located anywhere on the hill. Serpent Mound is only a mile west of here, so maybe this was the historical local Yucca patch. I’ve been controlling the spread of the Yucca, but because of the possible historical significance of its presence here, it’s not slated for elimination.

The Yucca may not be native, but there’s something on the plant that attracts the Mound Builder Ants. While these guys were reacting to the proximity of the camera, several of their colony mates were gnawing on my ankles.

I found this stink bug probing around on the back side of a Yucca seed pod. It was trying to avoid me by scooting around the pod, but it ran into the flower stalk.

There is only one insect that can successfully pollinate the Yucca flower. The female Yucca moth makes a hole in the flower’s ovary into which she deposits her eggs. She then fills the hole with pollen, which results in fertilization and seed development. The developing moth larvae then feed on Yucca seeds. The plant needs the moth and the moth needs the plant, a condition known as mutualism.

Inside a growing seed pod are rows of developing seeds. I’ve never seen a Yucca moth or the larvae or any holes in the seed pods or seeds that look as though they had been nibbled. If moths are the sole pollinator, they must be present, because the plants produce seed every year and spread to new areas through the distribution of fertile seeds. Why is it that after several years of searching, I’ve never been able to find any evidence of this moth? Is there actually some other pollination mechanism at work here?

Yucca

This is Yucca filamentosa, a non-native plant commonly seen in landscaping. Yucca was often carried by settlers and planted near the homestead

Apparently, by breaking the tip off the leaf and pulling away the attached filaments, you could use it as a crude needle and thread for mending clothing. The filaments are usually seen unraveling from the leaf margin.

Yuccas are attractive plants. Stands like this remind me of Florida. This is a very hardy plant that can survive some pretty severe growing conditions

The long waxy leaves funnel rain water in towards the base of the plant. This concentrates the water from a large area right to the root system. This also causes a corresponding dry zone that reduces competition from other plants trying to grow around the base of the Yucca. Besides robbing the surrounding area of moisture, the thick bunch of leaves almost eliminates sunlight penetration.

The Yuccas are beginning to move out of their grove of trees and spread through some of the prairies. I figured the seeds would move down hill into the dense cedars where the seedlings would die for lack of sunlight. These plants are moving up a steep slope and it’s time for me to put a halt to their progress. My next five year management plan will definitely have a section on Yucca control.

I’ll have to do some trials to discover the most effective control technique for Yuccas. A normal concentration of glyphosate is not terribly effective in killing this plant because of the difficulty in getting good coverage on all of the leaves. Even with a surfactant to break up the wax coating in the leaf, the herbicide tries to bead up and roll off the plant. Trying to get total spray coverage also results in a lot of dead nontarget plants in the vicinity of the Yucca.

One technique I’ll try is the application of a higher concentration of herbicide to the center of the leaf whorl in the spring. The rapidly growing leaves may take in enough herbicide for an effective kill.

After a couple of years the dead leaves of the Yucca create a thick mulch around the base of the plant. This is another way that this plant conserves moisture for itself and discourages other plants from germinating. Another control method I’ll try is cutting the Yucca off at the base and applying herbicide to the stump. Without the herbicide, the Yucca would send up new shoots and continue to grow.