The foremost aim of Permaculture is to work in harmony with nature and improve the quality of the soil, which is the unquestionable foundation of our gardens and forests. Chop and drop is a system of creating mulch whereby we are emulating nature’s natural soil building process, where leaves, branches, logs, and all forms of organic matter fall to the forest floor and eventually decompose into rich soil.
Consequently, it requires very little input and provides bountiful yields through improving soil quality and richness in far less time and with less effort than using a typical composting system. Your average compost pile requires you to balance your greens and browns, monitor temperature, and turn the pile periodically, which can be quite labour intensive if you’re producing a lot.
Instead of pulling up your annual plants and vegetables at the end of the season and placing them in the compost pile, and waiting a year or more for the nutrients to be redistributed, we can speed up the process and even make it more efficient and tailored to our needs by mimicking the way that rich soil is created in forests.
By intelligently choosing fast-growing species suited to our environments, we can ensure good quality mulch, year after year. This is especially important in the early days of starting a food forest or any other biologically diverse place, where focusing on building up soil fertility is a primary concern.
Any plant can be grown for chop and drop but certain ones excel at this process. These plants will typically grow back after heavy pruning very quickly, their leaves may contain an impressive arsenal of trace minerals, or their roots might release nitrogen fertilizing nodules when the branches are cut.
Some species that flourish for chop and drop contain deep tapping roots, giving them the ability to reach far below where other plants can, which have a more superficial root system. Consequently, they can draw up trace minerals and nutrients from below the surface, and when the leaves are cut and left to mulch, make these nutrients available to the other species with more shallow root systems.
Such species are known as dynamic accumulators. Some well-known examples of these are comfrey and clover, which are often grown as ground cover crops to prepare the land before sowing.
Nitrogen-fixing plants are another popular set for chop and drop, and for good reason too. When they decompose, they provide extra nitrogen to surrounding plants. These plants, many of which are legumes, harvest their own nitrogen from their surroundings and store it in their roots. When they are cut the nitrogen is released both above the ground in the form of mulch from cut leaves and branches, and below the soil from the root nodules.
Nitrogen Fixing Species.
CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=33774
Robinia pseudoacacia
A fast-growing deciduous tree, native to North America, which is a member of the Leguminosae family, and is now naturalized in many parts of Europe. The flowers open May/June and are extremely attractive to pollinators. It’s an effective dynamic accumulator, collecting minerals and nutrients from the soil that can then be used in a more bioavailable form as fertilizer.
Leucaena leucocephala
Public Domain, https://commons.wikimedia.org/w/index.php?curid=610389
A lowland tropical American legume, which probably originated in the calcareous lowland soils of the Yucatan Peninsula. It thrives in limestone-rich soils (including highly alkaline soils). It is valued for its timber, as fodder, and as a food source for humans.
Inga Edulis
Paul Latham, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
A leguminous tree native to the humid American tropics, popular for its rapid growth, tolerance of acid soils, and high production of leafy biomass. The fruit pods contain a sweet, white translucent pulp reminiscent of cherimoya. It is commonly planted as a shade tree in coffee and cacao plantations.