Tree Crops are the most common perennial agricultural method. More specifically, orchards are one of the most common and successful forms of perennial agriculture. A well-maintained peach orchard will give you a steady crop for up to 20 years. An apple orchard can last up to 50 years and well-maintained pecan tree may very well continue to produce for up to 150 years. Our agricultural systems have been designed almost exclusively for staple annual crops. However, transitioning into perennial agricultural systems that can produce food staples is one of the challenges we´ll face in the coming years in order to create a sustainable form of agriculture.
The Functions of a Tree
A perennial agriculture system based on the cultivation of tree crops offers a number of advantages over the traditional annual agriculture methods of staple carbohydrates such as corn and wheat. While these systems to take several years to get established, once production has begun the main body of work is maintenance and harvest. Tree crops such as fruit and nuts, then, can become a staple of our diet without having to till the soil year after year.
Permaculture asks us to find several functions for every element. Trees are perhaps one of the most useful elements in any permaculture design. Some of the functions of a tree agriculture system include:
Harvest: From fruits to nuts to edible leaves and shoots to mushrooms, there are a number of food products that trees can provide.
Mulch: The leaf fall from deciduous trees provides some of the best mulch material for your farm and is fundamental in building overall soil health.
Prunings: The prunings from your tree agriculture system can be chopped and put into the compost pile or allowed to decompose right in the soil. Either way, small branches, and pruning are the best way to develop health fungal activity in your soil.
Shade: Trees provide shade which is not only great for resting on a warm summer day, but also provides a unique habitat for certain types of crops.
Air: Trees create oxygen and sequester carbon in the atmosphere. By transitioning into a perennial agriculture system based on trees, we can help to combat global warming.
Windbreak: While growing your food staples you can also protect other crops that are susceptible to winds.
Beauty: Aesthetics are often an overlooked function in our landscapes
Habitat: The more trees we have on our landscape, the more diversity of wildlife we´ll have. Bird poop provides one of the best sources of phosphate, and by increasing the trees on your land, you will benefit from a free source of fertility.
Perennial agricultural systems also allow for a more diversified production through stacked polycultures. This fancy permaculture term refers to growing different layers of perennial crops in one diversified system. Small Central American, indigenous farmers have been growing stacked polyculture systems for hundreds of years. The canopy layer of this system is usually made up of large trees such as breadfruit, jackfruit, mango trees, etc. These larger trees are managed to allow enough light into the sub-canopy layer to allow for small trees such as banana, papaya, and others. Below those small trees, perennial crops such as yucca, corn, and beans can be grown sporadically. Turmeric, ginger and taro root can be grown as a root underneath this system.
Whereas annual agriculture only grows one type of crop, usually a carbohydrate/protein succession, it only takes advantage of one “layer” of the growing possibilities. Stacked polycultures vastly improve production through growing different crops at different layers. While these systems do take time to get established, they offer some of the best opportunities for a productive system that improves the soil and ecosystem health.
Design Your Own Stacked Polyculture System
Even if you only have a ¼ acre of land, you can develop your own stacked polyculture. Before going out and planting all sorts of trees and bushes, take the time to design and plan out your system. Ask yourself the following questions:
1. What types of tree crops grow well in your climate?
2. Which large trees would offer you a large annual harvest while still allowing enough light for other species to grow?
3. What types of fruit and nut trees could you plant in the sub-canopy layer?
4. What species could make up the shrub layer, ground cover layer, root layer, and fungus/mushroom layer of your stacked polyculture?
5. What are some potential opportunities for mutual benefit between the different species you plan to plant?
6. What work will you need to do during the establishment period?
7. How long will it take before the system is established and producing?
In temperate climates, one of the best examples of a perennial, tree-based agriculture is the concept of Restoration Agriculture as developed by Mark Sheppard of New Forest Farm in Wisconsin. Sheppard was convinced that instead of relying on annual carbohydrate crops such as corn and what that were ruining the land, perennial growing nut crops such as chestnuts and hazelnuts could provide our industrial food system with a staple carbohydrate crop that was healthier and more ecologically beneficial.
Sheppard has developed a restoration agricultural system on his own farm where he combines a diversity of fruit and nut trees planted on contour. In between his chestnut and apple tree rows, he grazes pigs and other livestock on pasture. According to his website, “Over the last 15 years, Mark has planted an estimated 250,000 trees on his 106-acre farm. He uses agroforestry systems and alley cropping and silvopasture techniques. The main crops are chestnuts, hazelnuts, and apples. He also grows walnuts, hickories, pine nuts, and pears, together with cherry trees, asparagus and winter squash. Cattle, pigs, lambs, turkeys, and chickens also roam on the restored savannahs at New Forest Farm.
Restoration agriculture systems intend on mimicking the different natural systems that are found in the region. In the case of New Forest Farm, the oak savannah ecosystem is what Sheppard tries to imitate through his diverse plantings.