building a pernnial keyhole bed

 A SMALL experiment in edible permaculture

Written by dave, one of our volunteers

Over the winter and spring 2025/6, we built and planted a 6-foot keyhole bed, aiming to create something that contributes to the existing forest garden at the Sustainability Centre (East Meon), originally designed by Patrick Whitefield. The aims were for it to be productive, perennial-led, based on permaculture principles, and easy to manage.
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Rather than focusing on annual vegetables that require sowing, lifting, storing, or processing, the idea was to create a “pick-and-eat” system—a bed that can be walked up to throughout the year and harvested directly from. We are particularly interested in how far a small space could lean towards self-management using perennial crops and layered planting.

why a keyhole bed?

The circular keyhole design gives excellent access to the whole bed without stepping on the soil, while also creating a compact, highly productive growing space. Ours is approximately 6 feet in diameter, built as a raised bed with a central composting basket for compostable such as organic matter from weeding, and kitchen scraps, which feeds the surrounding soil over time.  The timber for the keyhole bed is reclaimed oak rails that are from an old fence on the site.

building the bed: layering for soil health

The South Downs climate and chalky soils shaped some of the planting decisions: drought tolerance, perennial structure, pollinator value, and long growing seasons were all considerations.  Once the timber work was complete, the bed was built using layered organic materials including sticks and woody prunings at the base, followed by leaf mould and a compost-rich growing layer above. The approach borrows from both hugelkultur principles and no-dig gardening methods.

The woody material at the bottom acts as a long-term carbon store and slowly decomposing sponge, helping with moisture retention and encouraging fungal activity within the soil profile. This is particularly useful on the free-draining chalk soils of the South Downs, where summer dryness can become an issue.  Above this, leaf mould was added to increase organic matter and support soil biology. Leaf mould is especially valuable for improving soil structure, water-holding capacity, and fungal diversity.  The upper compost layer provides immediately available nutrients for establishment, while the lower layers are intended to release nutrients more gradually over time as decomposition proceeds.

Together, the layers aim to create:
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• improved water retention
• reduced need for irrigation
• active soil biology
• slow nutrient cycling
• increased carbon content
• minimal soil disturbance over time

designing for function: plant guilds

One aspect of the project was thinking in terms of ecological roles rather than simply crops. Each plant contributes something different:
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• nitrogen fixing
• pollinator support
• weed suppression
• biomass production
• vertical structure
• perennial leaf harvests
• soil shading and moisture retention

​The hope is that, once established, the bed will require relatively little intervention beyond occasional mulching, selective editing, and harvesting.

The planting scheme

The bed was designed around several “guild” layers rather than traditional rows.  A central feature is Caucasian spinach (Hablitzia tamnoides), a perennial climbing spinach that should eventually form the vertical layer of the system. Around this sit the main structural edibles, including perpetual kale, chosen for its reliability and long harvest season.

Alongside these, we have included several unusual perennial root crops:
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• oca (Oxalis tuberosa)
• Chinese artichoke (Stachys affinis)
• Peruvian earth apple (Apios americana)

The lower layer (both in the bed, and at the base of structure surrounding it) will evolve, and may include mixes of edible ground covers and herbs such as:

• oregano
• thyme
• nasturtiums
• perennial onions
• self-seeding salad plants

These will be included partly for experimentation and partly to explore how tuber crops function within a densely planted perennial guild.  Particularly, flowers such as nasturtium and companion herbs can help support pollinators and beneficial insects.

early observations

Although newly planted, the bed already feels different from a conventional vegetable plot. The diversity of leaf shapes, growth heights, and growth habits creates a more naturalistic appearance, somewhere between ornamental planting and edible gardening.

The challenge now will be balance: preventing dominant plants from overwhelming slower growers, while allowing the system enough freedom to become self-sustaining.

What are we hoping for?

Ultimately, this is an experiment in whether a very small space can support:

• year-round grazing harvests
• high biodiversity
• reduced watering and weeding
• resilient perennial food production

​If nothing else, it has already become a conversation piece, both with staff and volunteers, and with visitors who are asking questions about it as they walk by.