The Keyhole Garden in May of 2019
My keyhole garden turned 1 year-old the other day, here’s a few things I learned along the way
Of all of my projects over the past couple of years, the keyhole garden has been one of my favorites. Not only was it fun, easy and fairly cheap to build, but it’s been way more productive than I ever imagined.
The keyhole garden turned one year old a few days ago and the spring / early summer plant transition is in process. As this is my second time around, I’m adjusting a few things based on what I learned last year.
If you’re thinking of starting a keyhole garden or similar raised garden bed, or if you’ve tried in the past but things didn’t go well, here’s a few lessons I learned that might help you:
Lesson 1 : If it’s a new bed, don’t skimp on soil
Keyhole gardens are designed to take bad dirt and turn it into fertile soil by composting organic matter both in the middle of and under the bed. But unless you want to wait a full season, for that to happen, you’re best off using a loamy, weed free, compost soil blend.
Where I live the soil is primarily decomposed sandstone. It drains well when loose, but has little nutritional value and is hard as concrete when dry and compacted (which is most of the time).
Knowing that, I opted to bring in a soil mix that was primarily compost and manure. My neighbor built the same type of garden but used fill from another section of his yard.
We both had a pretty good late spring / early summer harvest, but under the heat of the late-summer San Diego sun, his bed turned to one with a giant stone slab on top that no water or plant could penetrate. His plants fried but mine thrived sponging up moisture and nutrients from a good loamy soil.
Lesson 2 : Make sure there’s access all the way around the bed
This is an obvious one, but I forgot it anyway. The keyhole garden is circular to allow you easy access to any part of the bed without a big reach.
If you don’t have clear access all the way around (because, say, you let a bunch of butterfly iris’ grow in the back since they looked nice from the dining room window), you won’t be able to maintain the stuff you can’t reach. That will grow and spill over into other places until you can’t reach them either. Before you know it, a third of the bed is a jungle scene from Jumanji.
Avoid the potential battles with man-eating vegetables by making sure you’ve got a path all the way around your keyhole bed.
Lesson 3 : Mulch, mulch, mulch
A keyhole garden has really good drainage, which–most of the time–is a good thing. But that great drainage also means the top inch or so of your soil can get hot, dry and roasty, or frozen solid rather quickly.
Either way, anything young or shallow rooted in the bed will get fried. A good layer of fine mulch (nothing with big chunks of bark or wood), solves this and gives you a nice bunch of organic matter to turn back into the bed later.
Personally, I’m gifted with a gigantic podocarpus whose main hobby seems to be proving that it’s possible to drop a 30 gallon trash bin’s worth of tiny leaves every week, so I’ve got plenty of mulch onsite. But any sifted compost, shredded coco, etc. will work.
Lesson 4 : Feed and turn your compost bin
The compost bin in the center of the keyhole garden is the nutrient engine for the bed, but once the garden is growing, it’s easy to forget that it’s central to the garden (literally).
Make sure you feed it regularly with vegetable scraps, coffee grounds, eggshells, and plant debris from your garden.
And turn it every couple of weeks too. Yes, it’s icky, but doesn’t smell and turning the bin’s contents with a shovel or garden fork will move uncomposted organic material to the center where your worm friends can turn it into rich, nutritious worm castings that seep back into the garden.
When you do turn it, note how many worms are in your soil. Mine looks like it’s 90% worm and 10% compost. Soil that is very much alive!
Lesson 5 : Plant shorter varieties
My final word of advice is to pick smaller or dwarf varieties to plant in your keyhole garden.
Because it’s designed so the gardener doesn’t have to stoop or bend (much) when tending it, it’s a little higher than your average raised bed. If you’re growing trailing or bushy plants, it’s great. Very convenient.
But, if you plant things like big indeterminate tomatoes or tall corn, you’re going to find the combination of the bed and plant height will make it so you need a cherry picker and safety net to harvest them (learned that lesson the hard way).
Well, that rounds out the big lessons I learned during my first year with the keyhole garden. I am still really impressed with how simple and productive it is with little-to-no effort on my part.
My new goal is to keep it in continuous production year round by doing a better job of planning plant transitions. Last year I didn’t do that and the bed had a week of down time between clearing out all the spent summer plants and replacing them with fall and winter. This year I’m hoping to just keep rolling through all four seasons with no gaps. I’ll let you know how successful I am.
If you’re interested in building your own keyhole garden or just seeing how mine has progressed through the year, check out the timeline of blog posts below. It’ll take you all the way back to the beginning.