This week I present some of the information on designing and installing your forest gardening found in The Ohio State University Extension Fact Sheet, Forest Gardening in Ohio. Although the particular plants discussed in the fact sheet are specifically chosen for the state of Ohio, the general information on forest gardening design and installation applies anywhere.
How to design a forest garden:
"In a natural forest, plants belong to one or more layers.
There are the high canopy trees, and an understory of shorter
trees. Beneath the trees is a layer of saplings and shrubs and
beneath that a layer of herbaceous plants. Just above the forest
floor are groundcovers. Finally there are the vines, which
grow up through all the layers. The key to designing a forest
garden is to think vertically—how many plants can I stack
into this space? Suggestions for plants for each of the layers
can be found in the plant list below. For a new garden area
or yard, plans can be drawn up from scratch. Forest gardens
can also be built around existing trees or shrubs, or in established
woods. For very small spaces, such as an urban back
yard, the canopy layer can be omitted, and the design built
around a dwarf fruit tree.
The plant layers in a natural forest are not uniform across
space. Different species live on high slopes as opposed to in
a river bottom, for example. Forest composition is different
at the edge of a clearing from the center of a large wooded
patch. Similarly, in a forest garden we design with the environment
and according to our specific uses. If one corner of
a forest garden is more poorly drained than another, that
corner should include plants that can tolerate having “wet
feet.” A forest garden can be set up like a forest edge, with
low growing species to the sunny side and taller plants in the
rear. Forest gardens can perform structural functions, such as
screening an unpleasant view or cold wind, or, if mostly
deciduous, can shade a house in the summer and let the sun
in to warm it in the winter. Aesthetic concerns are also
important. The principles of grouping plants, achieving balance,
and creating harmonious designs that are covered in
basic landscape design texts still apply to the forest garden.
Natural forests grow magnificently with no human intervention.
Forest gardens too seek to provide many, if not most,
of their own needs. A sheet mulch (explained in the installation
section) will keep the plants moist without the need for
much additional irrigation, and, as it breaks down, will furnish
the plants with valuable nutrients needed for their growth.
To increase the fertility of the system, forest gardens often
include nitrogen-fixing plants and plants grown specifically
to provide mulch. Forest gardens also often include insectary
plants to attract and support beneficial insects that can reduce
pest populations. Perennial and self-seeding plants are emphasized
in forest gardens because they reduce the need for
the annual chores of starting and planting out seedlings. Designs
may also include habitat for birds (who spread seeds, provide
fertilizer, and eat insects), toads (who eat insects), and snakes
(who eat rodent pests)."
How to install a forest garden:
"The ideal time to start a forest garden is in the fall. Trees
and shrubs can be planted if they are already on hand. Plant
trees and shrubs even with, or slightly above the existing
ground level. Next, lay down a sheet mulch. If trees
and shrubs are not ready, begin with the sheet mulch.
The first step in preparing a sheet mulch is to knock down
all existing vegetation. Knocking down is different from pulling
up or tilling under. Depending on the vegetation, use a mower,
weedwhacker, bush hog, scythe, pruning shears, or your feet
to break off all undesirable vegetation at or just above ground
level. Sod can be left in place and the sheet mulch laid on
top of it. Substantial woody vegetation can be removed for
chipping and later use as a path or part of the mulch. Thick
woody roots may also be removed. These can be brought back
later to serve as wildlife habitat or mushroom logs above
ground. Otherwise, leave everything to decompose in place.
If the soil is compacted, break it up with a spading fork
(one with a metal handle works best), a U-bar, or, for large
areas, a subsoiler. With the fork, insert the tines to their full
depth and lean on the handle. The object is to break up the
soil without turning it over.
Now is the time to introduce soil amendments. A soil test
will show whether it is necessary to adjust the soil pH with
lime (to increase alkalinity) or with sulphur (to increase
acidity). Also add any nutrients in which the soil was shown
to be deficient. An inch or two of compost will immediately
add organic matter and nutrients to the soil and is the best
all-around amendment. Next, add something rich in nitrogen
to draw worms to the surface and aid in the decomposition
of the carbon-rich layers that are going on top. Composted
manure is an excellent source (add 1/2 to 1 inch), as are fresh
vegetable scraps (a local grocery store or restaurant may be
able to provide these in quantity). All of these amendments
are laid directly on top of the soil one after the other and not
worked in.
Next comes the light barrier. The object of this
layer is to prevent the germination of weed seeds in the soil
and to provide a physical barrier to any weeds that do get
started. Two readily available materials for this layer are
newspaper and sheets of cardboard. Remove any glossy color
pages from the newspaper, as these contain metallic inks.
Remove tape and staples from the cardboard as much as
possible. Any solid 100% organic material can also be used,
including old cotton clothes or flakes of hay. Lay down
newspaper and cardboard so that the edges overlap substantially.
The newspaper should be anywhere from 4 sheets to
1/2 inch thick depending on the anticipated tenacity of the
weeds underneath. Around the trunks of trees and the bases
of shrubs, tear a section of newspaper or cardboard halfway
through, and slide the two edges of the tear around the trunk.
Tear a second sheet in the same way and place it perpendicular
to the first. It may be necessary to wet newspaper occasionally
with a sprinkler or hose to keep it from blowing around during
the installation process. The light barrier is the key to the
success of the sheet mulch. It takes some time to lay it with
care, but it can save many hours of weeding later. Do not be
alarmed if the newsprint on the light barrier is still legible as
much as a full season after installation. Eventually it will break
down and contribute to the organic matter in your soil.
On top of the light barrier, place another layer of nitrogenrich
manure or vegetable scraps. Then lay up to 12 inches of
bulk mulch. Bulk mulch can consist of leaves, grass clippings,
straw, wood chips, pine needles, branches, reeds, or any
uncomposted rough organic matter. The mulch can be placed
in discrete layers, or mixed together. It need not be uniform.
Leave some space around tree trunks and the bases of woody
shrubs. Otherwise rodents may come to live in the mulch and
nibble on the tree trunks. If rodents are a likely problem, cut
a slit in a metal can and place it gently, like a sleeve, around
the base of the tree. Two considerations are important for the
bulk mulch. One, avoid material that may contain seeds, such
as hay and weeds. These materials can be included in a sheet
mulch, but they should go beneath the light barrier. Two,
creating a balance of carbon-rich “browns” and nitrogen-rich
“greens” will help the mulch break down more rapidly. The
ideal ratio of carbon to nitrogen is around 30:1. Composting
books have much information on how to achieve this ratio
with different materials. An easy recipe is to mix fallen leaves
with fresh grass clippings and apply this as the mulch. If
the crucial C:N balance has not been achieved, the mulch
will still break down, but it will just take longer. To hasten
the process, use compost or manure teas as described below.
On top of the bulk mulch one can place a final layer of
hard mulch to make everything look tidy. This hard mulch
could be straw, bark mulch, wood chips, or pine needles.
It is best to let a sheet mulch compost for a period of time
after installation. If the mulch has been installed in the fall,
it will partially break down over the winter to create rich
garden soil. If it has been installed in the spring, it may only
be possible to wait a few days or weeks before planting."
Forest Gardening #008 will take a look at planting your forest garden. It should be posted next Friday. If you like this series and want to make sure you don't miss any of it, be sure to subscribe to this blog by email (it is free!). Look in the upper right corner of this page for the sign-up.
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