A plant guild is a community of plants that grows well together. Synthesizing these conditions involves mimicking how plants grow in natural ecosystems. In forests, savannas, and prairies, some plants grow well together and influence each other positively, and some don’t.
When they don’t have a beneficial impact on each other, plants can be either neutral or harmful to each other. But that’s not the end of the story. A plant can have an adverse effect on another while not being injured by the one that it is harming.
Black Walnuts are the best example of this phenomenon. To some extent, every tree in the Juglans genus has a significant impact on the plants around it.
Why does a walnut guild prevent other plants from growing and yielding well?
The reasons are multiple, as the walnut tree (especially when it’s mature) modifies its environment in powerful ways.
1. Walnut leaves contain a natural and potent herbicide called juglone that prevents some plants from growing and thriving. The same allelopathic substance is excreted through the walnut’s roots. Young plants are especially susceptible.
2. Walnut trees cast quite a dense shade. Not every plant will grow well or yield well near a plant that blocks out that much sunlight.
3. Walnut is a very thirsty tree. It requires a significant amount of water, and its extensive root system is very efficient in getting water from the soil first. Other plants can get their share only after the walnut is well hydrated.
4. Walnut trees require a vast amount of nutrients. Again this tree “eats” first, and other plants “eat” only whatever nutrients are leftover. If the soil is poor, the plants are not going to thrive.
Let me rephrase it: We have plants that are constantly:
- attacked by herbicide
- deprived of sufficient light
- left without sufficient water
…and we are wondering why they are not growing and producing well???
How efficient would I do my job if I were feed poison every day, kept in the basement all the times, and had my water and food intake limited?
Now, when we have identified a problem, we know what we need to do to solve it. We, the permaculture folks, know that if life gives you lemons, the best thing to do is to make lemonade!
How do we make a walnut guild more productive?
We need to make sure the plants have the best growing conditions possible.
We can significantly improve the conditions that are often limiting yields:
1. We can’t do much with the juglone produced, so we have to accept it and only use plants that are juglone tolerant to some extent. If necessary, we can remove fallen leaves, nuts, and husks.
2. If the plants aren’t growing well because there’s not enough light, we can prune the trees. Black walnut develops leaves late in the season and looses them early, giving potential for plants in the underbrush to use sunlight at that time.
3. There are plenty of ways to improve the amount of water that will be available for our nut trees (and the whole walnut plant guild). Planting walnut trees below a swale is one of the options. Implementing Keyline Plan on our property is another way we can make sure our productive trees and shrubs will give us abundant yields of high-quality nuts and fruit.
- Trace elements
They are all necessary for our plants to thrive. If the levels of nutrients are low (as indicated by a soil analysis), we should consider adding them to our soil. Otherwise, they will not be in optimal amounts in the food we are growing (and the yields will be lower and of poor quality).
Remember, we want to grow a lot of food in the same area, so we will be removing a lot of nutrients. In fact, if we want to grow twice as much food as in a commercial walnut orchard, we should deliver almost twice as much nutrients as the commercial growers. Why just almost twice and not twice as much? Nutrients in polyculture systems are simply being used more efficiently. With good, biologically active soil, we will not lose as many nutrients as a conventional grower will through leaching and soil erosion.
What plants can we use in a walnut guild?
There are plenty of plants not affected by juglone that we can use in the food forest.
Toby Hemenway described an interesting plant guild for a walnut tree in his book, Gaia’s Garden – a Guide to Home Scale Permaculture.
It consists of:
- Walnut – English or Black Walnut (Juglans spp.) – for nuts
- Hackberry – food for wildlife
- Wolfberry – food for wildlife and medicine
- Peppers or tomatoes
- Elaeagnus (Elaeagnus spp.)
- Mulberry – for fruit or fodder
- Currants – for fruit
- Elderberry – for very edible flowers and fruit
I think that Toby Hemenway made a mistake recommending tomatoes in this guild, as tomatoes are very sensitive to juglone. Otherwise it is quite good, though it could be improved even more by adding more productive shrubs and an edible ground cover layer.
- Pecan or Walnut – English or Black, for nuts
- Huckleberry for wildlife food
- Autumn olive, gumi, or Seaberry for nitrogen fixation and tasty fruit
- Goji plant for tasty goji berries (superfood)
- Mullbery for fruit or fodder (berries and leaves)
- Elderberry for flowers and fruit
- Black currants for fruit
- White currants for fruit
- Red currants for fruit
- Gooseberry for fruit
- Fiddlehead ferns (ostrich fern, royal fern) for edible, asparagus-like young shoots
- Borage for greens, medicinal value and pollination
- Nettles for medicinal value, animal fodder, survival food and an insect attractant
Just remember, for this guild to work well, we need fertile soil with plenty of water…