Mandala and Keyhole Garden Beds for the Cold Climate Part 2

In the last newsletter we talked about how keyhole beds bring a new dynamic to garden beds:

• maximize growing space
• integrate functionally with the rest of your garden, sharing infrastructure, like windbreaks, fences, irrigation, mulch, and microclimate
• enable you to plant trees in the bed, which help the annual plants
• enable you to create a rotation with animals, which work the soil for you

Now, let’s learn how to implement them.

First we will learn how to create the mandala garden bed. Then, single keyhole beds follow the same principles.

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In this edition, in 4 minutes or less:

#1 How to implement a mandala bed

#2 How to Implement a Keyhole Bed

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How to implement a mandala bed

We’ll break the mandala (an assembly of 6 keyhole beds) and the keyhole beds themselves into functional “components,” then explain how to assemble them.

A complete mandala requires 10–12 meters (33–39 feet) in diameter, so begin by locating a relatively flat space between 100 and 144 square meters (1,075–1,550 square feet).

Component 1: The Central Hub

This core anchors water infiltration, produces yield, fertilizes soil, and inoculates beneficial fungi (particularly if you plant a nitrogen-fixing tree with mycorrhizal partnerships, such as a legume).

Focus on trees that are nitrogen-fixing, yield food for animals and/or humans, and produce abundant mulch—in other words, genuinely useful trees. Excellent examples for cold climates include:

• Tagasaste (Chamaecytisus proliferus or Chamaecytisus palmensis) — Nitrogen fixer, animal fodder
• Siberian Pea Shrub (Caragana arborescens) — Nitrogen fixer, animal fodder
• Hazel (Corylus avellana) — Animal fodder
• Black Locust (Robinia pseudoacacia) — Nitrogen fixer, animal fodder, bee forage
• Honey Locust (Gleditsia triacanthos) — Nitrogen fixer, animal fodder, bee forage
• Apple (Malus spp.) — Animal fodder, bee forage

Alongside these trees, you can plant cover crops that protect soil from erosion, support tree development, provide food, and produce mulch:

• Lavender (Lavandula spp.) — Bee forage, pest deterrent, soil improvement, medicinal uses
• Globe Artichoke (Cynara cardunculus var. scolymus) — Dynamic accumulator, insect habitat, chop-and-drop mulch
• Comfrey (Symphytum officinale) — Dynamic accumulator, prolific chop-and-drop mulch, bee forage
• Clover (Trifolium spp.) — Nitrogen fixer, living mulch, bee forage
• Yarrow (Achillea millefolium) — Insectary plant, drought-hardy, living mulch edging
• Borage (Borago officinalis) — Bee forage, mineral accumulator, edible flowers and leaves
• Dill (Anethum graveolens) — Insectary plant, attracts beneficial wasps, umbellifer guild support
• Nasturtium (Tropaeolum majus) — Edible ground cover, trap crop for aphids, flowers attract beneficials

Construction Steps

Step 1: Mark a circle 2 meters (6.5 feet) in diameter at the center of your 100-square-meter (1,075-square-foot) area.

Step 2: Excavate or create a mound, depending on whether your area needs more moisture or better drainage (here, we use earth shaping as a microclimate tool).

Step 3: Plant the tree following our tree-planting instructions from previous newsletters.

Step 4: Plant the space between trees with useful plants such as nasturtium, comfrey, clover, lavender, and globe artichoke.

Tip: Choose your trees carefully. Select species you like, that are useful, and that are hardy for your climate zone. Consult local tree nurseries for recommendations. ### Component 2: Paths

These paths are multifunctional:

• They capture and infiltrate rainwater
• Useful perennials can be planted at keyhole junctions (pay attention to orientation and height so they don’t shade your garden)
• If you build paths from sawdust, you can inoculate them with fungus to enrich soil and even harvest mushrooms

photo of fungus on our garden #### Materials Needed:

• Sawdust or gravel for paths

• Soil for banking bed edges (10-20 cm high)

• Paper and mulch (same as the central circle)

• Tagasaste, Siberian pea shrub or black locust tree (optional)

Construction Steps:

Step 1: Around the central circle, create a sunken path 0.6–1 meter (2–3.3 feet) wide. Cover with sawdust or gravel.

Step 2: From this circular path, create 5–6 “keyhole” indentations—paths extending outward like fingers.

Step 3: Surround each keyhole with a raised bed 1.5–2 meters (5–6.5 feet) wide.

Step 4: Bank the bed edges 10–20 cm (4–8 inches) high to prevent water runoff.

Step 5 (optional): Plant Tagasaste, Siberian pea shrub, or black locust at each keyhole junction (see image).

Step 6: Cover each bed with paper and mulch—approximately 30 cm (12 inches) of compacted, wetted mulch.

Tip: Construct during the dry season when soil is easiest to work. Complete construction 4–6 weeks before the wet season begins.

Component 3: The Keyhole bed

As explained above, the keyhole bed is a circular garden with a path leading to its center—resembling a keyhole from above. When arranged geometrically, as in a mandala, they create a super structure of enhanced functionality. It is an exemplary polyculture bed, allowing you to maximize the benefits of this strategy naturally.

The growing space divides into three zones:

Zone “a”: Inner Edge

Dedicated to daily-harvest crops (herbs, greens, frequent picks).

Zone “b”: Middle Strip

Crops with longer harvest periods (weeks or months). Accessible from the path but not harvested daily.

Ideal placement for trellises—as long as they don’t shade other plants.

Zone “c”: Outer Edge

Crops you harvest and replant once—slow-growing varieties that occupy space for months. So, positioning them at the outer edge keeps high-traffic paths clear.

Component 4: The weed barrier, mulch system, and fence

This is a completely new concept for someone that has grown food following main stream gardening advice.

However, it has been practice by our ancestors for millennia.

A garden bed is a structure made by us humans, and nature will try to claim the space back. So, in order to prevent it, plant a guild of plants between your garden bed and the surrounding landscape. This guild will suppresses weeds, produces continuous mulch, provides windbreak protection, and creates favorable microclimates—”stabilizing” your growing space.

The whole garden can be fenced to exclude wild animals, if necessary.

Inner Barrier: Between Keyhole Beds

Low-growing plants that suppress weeds, prevent erosion, and provide early harvest

• Tree Onion (Walking Onion, Egyptian Onion) — zones 3–10; perennial, edible greens & bulbs year-round; cold-hardy to -24°F
• Sunroot (Jerusalem Artichoke, Sunchoke) — zones 3–9; edible tubers, deep-rooting, biomass production; cold-hardy to -30°F
• Wormwood (Artemisia absinthium) — zones 3–9; aromatic, pest-repellent, silver foliage; cold-hardy to -20°C; replaces Rosemary
• Hardy Geranium (ground-cover types) — zones 3–9; dense weed suppression, attractive flowers; cold-hardy to -40°F

Middle Barrier: Continuous Mulch & Nitrogen Production

Medium-height plants that produce abundant biomass, prevent weed invasion, and create microclimate

• Comfrey — zones 3–9; nitrogen-fixer, prolific leaf production, cold-hardy to -40°F; excellent for chop-and-drop mulch
• Jerusalem Artichoke — zones 3–9; tall (6–10 ft), edible tubers, biomass & shade; cold-hardy to -30°F
• Peppermint or Spearmint (hardy Mentha species) — zones 3–9; spreads via rhizome, aromatic, pest-deterrent; cold-hardy; replaces Lemongrass
• Feverfew (Tanacetum parthenium) — zones 3–9; dense growth, pest-repellent, cold-hardy; alternative to tender ornamental flowers

Outer Edge: Windbreak & Boundary

Tall, dense border that provides wind protection and creates a visible edge without casting excessive shade

• Pampas Grass (Cortaderia selloana) — zones 5–7 to 11; dramatic height (8–12 ft plumes), dense structure, cold-hardy to -20°F in zone 5
• Jerusalem Artichoke(serves dual role as mid and outer layer) — tall yellow flowers, structural presence, productive
• Feather Reed Grass (Calamagrostis × acutiflora ‘Karl Foerster’) — zones 3–8; 4–5 ft tall, very cold-hardy, compact form, excellent windbreak
• Miscanthus (hardy varieties like ‘Gracillimus’) — zones 4–9; 6–8 ft tall, ornamental plumes, cold-hardy
• Common Hawthorn or Sea Buckthorn — zones 3–7+; native shrub, dense, thorny, wildlife value, wind-tolerant; replaces Coprosma
• European Elder (Sambucus nigra) — zones 3–9; fast-growing, 15–20 ft, dense, edible berries, excellent windbreak; replaces Bannagrass

Fence:

For security or to exclude wild animals

• Post and wire
• Electrified
• Dry stone
• Spiny woven hedge

How to Implement a Keyhole Bed

Construct a single keyhole bed using the same methods as a mandala, but omit Component 1 (the central hub). That means:

1. Mark what would be the center of the circle and make sure that the whole area where the keyhole bed will land is suitable. Does any part of the area fall on a problem spot, like a depression or where there are too many stones? If you can’t fix this problem spot, move the bed, because it is easy to relocate it at this moment, than to deal with the problem for as long as you garden there.
2. Component 2: Paths
3. Component 3: The growing beds
4. Component 4: The weed barrier, mulch system and fence
   • Tip: you can place your keyhole bed near an existing house wall, or greenhouse wall (which are solid constructed with isolation and deep foundations) to stabilize a sector of your keyhole bed against weed invasion and to benefit from creating a microclimate effect–that is a tip for retangular beds as well. You will not have the benefit of mulch production in this setup, thought.

A single keyhole bed requires 3.5–4.2 meters (11.5–13.75 feet) in diameter, depending on weed barrier thickness (Component 4). You’ll need a relatively flat space between 12.25 and 18 square meters (132–194 square feet).

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It looks unconventional, but many people around the world are gardening with keyhole beds.

It is a very efficient way of gardening with nature, allowing you to really develop a practice without using chemical fertilizers and pesticides, because you are at the same time protecting and creating soil. Moreover, you are defending your garden from weather extremes and weed reinvasion. Beyond productivity, it creates a beautiful space, can be positioned along terrain contours, and is fully adaptable and modular. As an example, Linda Woodrow, an Australian commercial gardener and author, runs a commercial farmers market operation exclusively with her adapted keyhole beds and mandala beds integrated with chickens without any external inputs (chemical fertilizers and pesticides).

You can trust that it is an effective practice and try it yourself.

See you next Tuesday!

Alexandre and Marina

P.S.: Our guide is based on the keyhole beds design and teaches you to transform a home garden into a permaculture garden, like many other people already have.

Sources: Mollison, Bill, Remi M. Slay, Jeeves, Andrew. Permaculture: A Designers’ Manual. Tagari Publications, 1988, pages 270, 274-275, 420, Figure 10.23, Figure 10.26, Figure 12.5.

Mollison, Bill, Remi M. Slay. Introduction to Permaculture, Tagari Publication, 1991, pages 97-98, figure 5.3.