Growing Walnut Trees
As I noted in an earlier post, I’m keen on having a few nut trees on our property because they relate to childhood memories and growing up in Michigan. Walnuts were one of the nuts I collected as a kid! Through my research I’m discovering some surprising information. I will need to keep this in mind when determining which variety to plant and where to plant them.
Here is a brief overview on the Walnut
Research source:
Walnut trees are well-known for their tasty fruit – the walnut! These trees are excellent ornamental trees that provide plenty of shade and will attract wildlife. Perhaps if I order and plant large enough trees they could also act as my hammock posts! We were given a hammock as a wedding gift 26 years ago and have only used it once!
The most common Walnut trees include the Black walnut and the English walnut. Black walnuts can grow in hardiness zones 4 through 9, while English walnuts prefer zones 3 through 7. The most popular states to grow Walnut trees includes California, Illinois, Iowa, Indiana, Minnesota, and Missouri. I know they can also grow in CO, as one of the properties we looked at in Palisade last year, had them… I wonder what variety they were?
English walnuts are the more popular walnut tree if you are looking to harvest the nuts. The shells are far easier to open than the Black walnut. A surprising fact I learned during my research was that all Walnut trees are renowned for their production of a natural herbicide called juglone! So, when I start mapping out the layout of our farm, I need to definitely keep this in mind as juglone in high doses is toxic to other plants!
That said, the English walnut’s concentration of Juglone is lower than Black walnut. Interestingly, Pecan trees also produce juglone but also at lower levels.
The key thing to remember is that when identifying the location of my Walnut trees, I need to avoid planting other things around it. This also means I need to pay attention to how close I place it next to our neighbors’ property as well. Juglone is a naturally produced toxin and almost every part of a walnut tree (especially the Black Walnut) will produce juglone. The roots, twigs, bark, and fruits all produce this brutal chemical. Even a Black walnut that is cut down could still be contaminating the soil a decade later with the decomposition of its roots. Note to self, DO NOT PLANT BLACK WALNUT!
So now that I’ve determined no Black Walnuts for me, I will focus on the English Walnut, keeping in mind that it as well as the Pecan do still produce this toxin and that I need to be mindful of where I locate the nut trees in relation to the rest of the garden, landscaping, and farm.
More on the English Walnut tree
Research Source:
The following excerpt comes from an article written by Les Engels and reviewed and updated by Andrew Hughes 02/22/2022
Native to central Asia, the English Walnuts are much easier to harvest than the black walnut (those toxin beasties that I will not be planting) as they fall without the husk and can be gathered with a garden rake and eaten raw or used in cooking! This sounds like an awesome bonus!
The English walnut is incredibly low maintenance; however, the following should be taken into consideration:
Light
The English walnut does not require a lot, however full sun is on its list of must-haves. You need to plant your tree in an area that receives at least six hours of direct sun a day. You will notice some deficits in production and growth if your walnut tree is not given ample light.
Soil
The English walnut is a big tree, and it will require good, fertilized soil to support its root system, which grows very deep and adequate drainage.
Water
Newly planted English walnut tree needs to be watered weekly throughout the spring and summer of the first two growing seasons of its life using a watering system from below, such as a soaker hose, to not wet the foliage… wet leaves, very bad! Be sure to release the water slowly so that it penetrates deep into the soil without running off. Once established, taper the irrigation off to a biweekly schedule.
Temperature and Humidity
Avoid hot and humid weather and climates as the English Walnut prefers the cooler climates associated with USDA zones 3-7. Palisade is zone 7 so I should be good to go on this point. Plus, as I said earlier, I know of at least one property that we’ve looked at that had Walnut trees on the property.
Fertilizer
Once established, it is a good idea to give the tree a regular boost of fertilizer in the spring. Using a slow-release high nitrogen fertilizer with ammonium sulfate will help keep the plant growing vigorously through the growing season.
Pruning
Pruning the English walnut should be done annually in the winter to establish a strong single leader and rounded crown structure with good lateral branching. This strategy clipping will allow room for the walnuts to grow. When doing these cuts, it is important to look for any weak, dead, or damaged branches and remove them.
What I’m discovering is there is a lot to keep track of if one is going to grow an orchard… and I’ve not even gotten to the fruit trees yet! I’m thinking I will definitely need to create an Orchard/garden calendar to keep track of all the pruning, watering, planting and harvesting… I might end up needing a whole calendar wall!
Another thing to be aware of are the nasty, little beasties that like to eat and or destroy nut trees!
Common Pests and Plant Diseases
The Walnut husk fly is the English walnuts’ most common nemesis. Fly larvae feed on walnut hulls and make their removal difficult. The walnuts will still be edible but less desirable as a food crop. Okay this sounds totally gross but obviously something I need to keep an eye on! To combat this pest, place landscape fabric under the tree canopy in late summer to prevent larvae from entering the soil. Additionally, remove all nuts that fall to the ground. Sprays labeled for homeowner use to control walnut husk fly can be used but be sure to consult the labels for exact instructions and warnings. I’m hoping not to use pesticides etc.. on our farm so I will need to do more research on how to combat this critter with sustainability/ organic approaches in mind.
The most serious disease for English walnuts is thousand cankers; the disease is caused by a fungus that the walnut twig beetle spreads. The disease is named thousand cankers due to the number of cankers that can occur in a single tree. Symptoms will include yellowing and thinning of foliage in the upper crown, branches dying off, wilting foliage, and eventually tree death. Once infected and symptoms appear, a tree will die in three years or so.
Types of English Walnut Trees
There are many cultivars of English walnut trees currently available, and more are being developed yearly. Each cultivar is specifically selected for a unique trait that makes it superior to the straight species. As English walnut is such a predominant food crop, most of these traits are developed to highlight needs in crop production, such as frost hardiness or nut production. The cultivars that highlight one trait are often placed on the rootstock of another cultivar or species to capture that host plant's more favorable trait. Some examples of well-known cultivars are:
Juglans regia ‘Caspian’ - leaf’s late to help avoid late-spring frosts. This Persian cultivar is similar to the Chandler.
Juglans regia '‘Chaldoran’ - has medium vigor and high fruit-bearing potential which offsets the risks of late-frost damage. This Persian cultivar is also similar to the Chandler.
Juglans regia ‘Alvand’ - slow-growing tree with abundant fruiting potential and long flowering season to offset frost damage risk.
Juglans regia 'Chandler' - cultivar developed at the University of California at Davis that is highly productive with medium-large, plump, light-colored kernels that have outstanding taste. One of the most popular cultivars available.
These last four bullet points, tell me where to go next in my research on the English Walnut tree!
Next up… the Chandler!
