Deer and Black Walnut my Challenges in the Garden

The past few years I have been planting trees on my property to replace the emerald ash losses, evergreen losses and a red oak that failed. I have had intermittent luck with garden specimens. This past summer’s drought was a challenge to the new trees I bought, but I was quite pleased with how well this bunch of  trees had done with their Gator bags through the hot and very dry summer we had here. I thought this new group of trees had made it.

Then the artic weather and snow of the last two weeks hit and the small herd of deer denuded the bottom half of my row of nellie steven’s hollies. Right now I have lollypop trees and I’m wondering if they can ever recover from the assault. Deer are not supposed to eat holly, so they must have been very hungry in the snow and cold. Two years ago, the deer denuded and killed my shrubbery on the other side of the house. So, I am a little heartbroken at the thought of loosing my formerly beautiful and thriving hollies. Though I have acres of woodland ending in a stream, my ornamental garden is seemingly a deer buffet.  I am constantly replanting and estimating deer desirability of plants.  

lower part stripped of leaves

the corner bush stripped of leaves

Deer are not my only challenge. My garden also has another significant challenge- juglone.  This substance is found in the vegetative buds, leaves, stems, nut hulls, and roots of black walnut and hickory trees (and a few others). Black walnut (Juglans nigra) and hickory are the primary culprits. I thought it quaint that our neighborhood was once called hickory grove. That is until I face the challenges of trying to garden around stands of black walnut and hickory trees.

The production of juglone is a protective response by the black walnut and hickory to assure their survival and reproduction by inhibiting nearby competition. The most common symptoms of juglone sensitivity in garden plants is the yellowing and wilting of leaves, especially during the hot dry periods of the growing season, ultimately resulting in wilting and death of the plant.

the black walnuts all over the yard

Early wilting can often be reduced with additional watering, but trust me, this will not work for long. Later in the season wilting does not respond to additional water, leaves start to brown, and the plant dies. Basically, black walnut and hickory kill off the competition. Worse yet, as neighboring trees grow larger and their roots spread towards the black walnut, they go into decline. Coming to Virginia from California 17 years ago I had no clue. It cost me several thousands of dollars in dead plants to send me to the extension office and finally be educated in juglone. According to the extension office, juglone inhibits plant respiration, depriving sensitive plants of needed energy and cell division as well as water and nutrient uptake.

Various sources of information have published lists of plants that are tolerant to juglone. They are based on observation under various settings, but few plants have been experimentally tested for sensitivity to juglone. It turns out that many factors affect sensitivity, including level of contact, health of the plant, soil environment, and the overall site conditions. My most challenging area is the east side of my house which abuts a black walnut stand. I have replanted the beds along that area several times. Any stress seems to exacerbate the problem.

Right now, I have the nellie stevens, green giant, cryptomeria, forsythia, lilac (that is struggling), and hydrangea. I hear that nine bark might work. Various source have lists of plants that will survive- I have not had success with many of them, and some of them are totally deer candy for example the Hosta. Nonetheless, I recommend checking out the lists from Virginia Tech and Penn State Extension as you, too, test your garden by trial and error.