Keyhole Beds Explained.

Keyhole Beds from the Gardener's Calendar

This is quite ingenious, with a traditional vegetable bed where you plant in rows, and to provide access to each row you will need a path. So for 5 rows you will need a minimum of 4 paths. If to save space you shuffle all the rows together so they are 1.5m in deep, you now only need one path to give you access to the whole bed. But wait, if you then curl the whole bed around into a circle 3m across, with a single path into the centres of the bed you can still reach all of the bed, but the path is only half the length. Plant your keyhole bed using the zone system so the most picked crops are next to the path and the least picked crops are at the back.
Some more benefits of the closer planting is to encourage competitive growth with the plants, and to make companion planting more effective.

Here is an example of a Keyhole Bed. 

(The path faces South)

Zone A - Lettuce, Radish, salad veg, and herbs

Zone B - Tomatoes, Peppers, and bush peas

Zone C - Cabbage, Potatoes, Onions, and Carrots

Zone D - Tagettes, Nasturtiums, Wormwood, and Tansy.

The Zones do not have to be filled with all of them mentioned vegetables and herbs, they are just given as examples of the type of crops you can use.

Depending on the exposure of the bed you can plant taller plants in Zone D at the top of the bed and it will protect against the cold Northly winds. This will create a small micro-climate within the bed.

We have setup a test Keyhole bed here, and will monitor it to see if the yields we get from the bed is greater than a traditional of the same size. The bed measures 8ft x 8ft and the path is 5ft long and 1.5ft wide. In the first picture the ground has been forked over to remove weeds, roots, and any stones. Then the soil has been dug to one spades depth, over the whole area. The entrance to the bed is at the south.
The planting has been quite compact with a complete mixture of vegetables. Around the outside of the bed we have put a border of Tagettes, then a layer of bush Courgette's, next is a line of Bulb Fennel, and on the inside is a double row of Basil. The whole area has been treated with NemaSlug, so hopefully once the beer traps have caught the adults, the rest will be finished off by the natural predators.