Spraying Walnuts

Walnut sprouts have just reached the stage where they can be successfully treated with glyphosate herbicide.  Walnuts are the most frustrating of the many plants that I control through use of herbicides.  They begin to grow late in the spring and then grow so rapidly that they quickly become too large to safely spray without killing everything in the surrounding area.

Each walnut was marked with a red flag as it was cut, so I would be able to find the sprouts now.  The warm temperatures early in the spring caused many plants in the vicinity of the walnuts to grow remarkably fast.  The sprouts are difficult to find in the mass of vegetation.

The compound leaves of the walnut spread far to each side of the stalk.  The small leaflets make it difficult to spray without also covering neighboring plants.  Fortunately, the area most affected by walnuts is thick with Tall Fescue and other farmland relics that also need to be eliminated.

Many walnut sprouts don’t spread their leaves until they reach heights in excess of one foot.  This means that you can’t safely spray on days that have any noticeable wind.  You also can’t spray if the leaves are wet with dew or if you are expecting rain.  So to successfully spray walnuts, you must wait for those few days that the sprouts are at the optimum size and hope you can find a few hours when it’s not dewy, windy or rainy.  That can be awfully hard to do.

My area of walnut infestation is in the field directly behind the house.  Since I look at this field every day, I’m trying hard to create a view without invading walnut trees. 

The walnuts in the field came from nuts produced by trees in the yard.  These trees were planted by the previous owner and are one of the worst trees to put in a lawn.  I finally got tired of dealing with the nuts and stopped mowing around the walnut trees.  Squirrels now do me the favor of carrying the nuts off and burying them all over the place.  I know that some people have trouble growing walnuts from seed, but at Blue Jay Barrens all you need to do to get a seedling is put the nut on the ground.

Black Walnut

The person who sold us our house had a liking for Black Walnut and planted several of these mighty nut producers in the yard. If you’re going to maintain a patch of mowed lawn, the last thing you should consider planting is something that produces thousands of hard, round balls that drop for weeks in the autumn. My solution was to just stop mowing under the trees. At least Black Walnut is native to this area.

I really like the openness of the Walnut canopy. It always reminds me of the airy trees scattered across the African Veldt.

My real aggravation comes from the forest of walnut trees that develop from the scattered nuts. Some people have elaborate methods for making walnuts germinate. At my house, all you need to do is let the nut hit the ground and you get a new tree. Squirrels and Chipmunks have helped distribute nuts far across the field and I am constantly trying to eliminate the resulting saplings.

Black Walnut is a common tree of the old fence rows. The origin of the trees is the question. Are any of these trees descended from a lineage native to this site or were the parent plants brought in from somewhere else?

Our shallow soils may be perfect for sprouting walnuts, but they provide terrible growing conditions. Walnuts grow best in deep soils. When the roots are stopped by shallow bedrock, the tree begins to suffer. Frequent branch die back, twisted trunks, rotten cavities and multiple trunks are common characteristics of the trees that grow here. These are not the trees that timber buyers dream of. Of course, producing timber is not one of my goals.

There are some older Black Walnuts in the old fence line. This specimen bears the scars of old fence wire. A 1938 aerial photo of the property shows a tree growing in just this location. I believe this is the tree I’m seeing in the photo, so I can imagine the age being near the 100 year mark.

In a little valley below the barn, a group of younger walnuts put on some rapid height in the deeper soil. The root system of Black Walnuts produces a chemical called juglone, which is toxic to many types of plants. As a result, a community of juglone tolerant plants develops in association with the walnuts. The ground cover in this valley changes dramatically as you move out of the walnut dominated area.

Walnuts on the other side of the barn show signs of having been planted in rows. I wonder if past generations had a similar interest in planting the valuable Black Walnut. I have not found any Black Walnut trees in the wooded portion of Blue Jay Barrens. That doesn’t mean they were never there. Walnut would have been readily cut if it had even the slightest economic value and could have been eliminated from the woods decades ago. The origin of Black Walnut at Blue Jay Barrens is just one of those things I ponder when I’m in a pondering mood.

Cutting Walnuts

I spent part of the day yesterday cutting areas infested with Black Walnut trees. This field is bordered by mature walnuts and the squirrels take the nuts and bury them everywhere. The result is a forest of walnut sprouts.

Many of these sprouts have been cut before. Not only cut, they’ve been sprayed with glyphosate herbicide and I thought, killed. It was quite a surprise when some of the cut stumps sprouted the next spring. They not only grew back, they sent up four sprouts for every one I had cut.

Everything you see here is the result of a single year’s growth. That clump in the foreground is nearly seven feet tall. If I don’t at least cut them each year, they’ll be 20 foot tall trees in just a few years.

Now they’re cut and marked. Walnuts are somewhat resistant to the herbicide I use, but that isn’t the reason I have trouble controlling them. Walnuts begin growing later than anything else in the field, so by the time I spray, the sprouts are hidden by surrounding foliage. Their growth is so rapid that there is only a small window when they are the optimum size for spraying. Weather and work often make me miss the best spraying date. The last concern is the fact that in late summer, when I should be giving the sprouts a second shot of spray, the chiggers have taken control of the walnut treatment areas. Whatever makes the walnuts grow so well here, must also spur the chiggers into reproductive excess. The thought of all those chiggers usually convinces me that my efforts are most needed elsewhere and the walnuts never get their second treatment.

The cut sprouts decompose quickly and won’t be noticeable next year. I think I’ll just have to ignore the chiggers this summer and make a determined effort the get rid of these walnuts.