One of the wonderful things about Permaculture is that it encourages to think about different shapes and layouts than just the rectangular shape so prominent in todays' world.
A keyhole garden bed is a garden bed that has a keyhole type area that allows working in a circle or semi circle and therefore reaching a larger surface area from one point than when working in a normal garden row. We have designed several keyhole garden beds and I have just finished planting the first plants into it. There is an onion circle (hardly to be seen in the photo below), a bean circle which is the visible by the holes. Around those there is a semi circle of tomatoes.
Since reaching past the tomatoes will be hard or impossible at a later stage, this is the outer most circle to be worked from the keyhole. The outside, planted with lettuce (left) and fava beans (top) can be reached from the paths.
I also have a side to the right of the picture, which is harder to reach, as the grass typically grows long and high and I don't mow that side. Therefore I planted squash and it will run into the grass and hopefully suppress it a little. In any case I will only need to access it later in the fall.
Since I like stuffing as much as possible into a bed, I planted some lovage in the free corners and placed a calendula on top of the tomatoes. The calendula will not only make the bed look pretty, but will also help keep nematodes at bay, although I am not sure whether this is required in this case. Nearly every hole I punched into the ground revealed a predatory insect that will help the soils ecosystems to stay in balance.
Keyholes can be put beside each other to make a whole row of beds. The look can also be very appealing (in our opinion anyway). We use them often in garden designs that are close to the house where space is limited. They also make fantastic herb beds right outside your kitchen entry, for that quick dash to spice up your dinner with that little bit of cilantro or and extra load of basil.