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Gardening by numbers

21 June 2021
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This garden has been divided up using polythene pipes.

Square-foot gardening has been around for decades, but is it right for your place? We take a look at the numbers.

Words Diana Noonan

If you’ve ever encountered a garden that’s carefully divided (whether by string or some other material) into a grid of identically sized squares, you will have some idea of the ‘square foot’ style of gardening. This method of growing was first unleashed onto the gardening world over four decades ago, and it has continued to attract devotees ever since. Its ‘inventor’ was American Mel Bartholomew.

Bartholomew, who died in 2016, was not only a gardener, but also an engineer, businessman, television presenter and author. Once retired, he became more interested in growing vegetables and, one day, when a composting tutor failed to turn up to the class he was to take, Mel and fellow classmates decided to take the matter of gardening into their own hands, and established a community garden.

Using the traditional method of ‘gardening in rows’, the community garden became infested with weeds and soon ground to a halt. That was when Bartholomew began to rethink the methods that gardeners had been using for – almost – ever.

He concluded that growing in rows was wasteful of space, labour-intensive, and unsatisfactory for dealing with pests and disease. To him, it seemed it was a method of commercial market gardening that had simply been downsized to fit into backyards – where it didn’t belong.

Commercial growing was geared towards allowing space for animals or machines to move along rows. These otherwise empty spaces received as much fertiliser and water as the rows of vegetables themselves and, because they were bare, attracted weeds that then had to be pulled. In all, Bartholomew concluded that 80 per cent of a commercial field was being unused for growing.

Commercial gardening, he also noted, involved mechanical sowing, something that inevitably led to the laborious task of thinning.

When Bartholomew asked fellow gardeners why they did things this way, they had no answer other than to say it was the way gardening had always been done.

Frustrated, Bartholomew soon developed a style of gardening that was, in his opinion, much more suited to the domestic grower. He was fond of saying that even beginner gardeners could master this method in a couple of hours – but that die-hard row-growers might take a lot longer!

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The upcycling-savvy square-foot gardener will see potential in old Venetian blinds.

Bartholomew’s beds
The answer to successful backyard gardening, for Bartholomew, involved dividing a raised garden bed into equally sized squares using clear markings, such as beading-sized strips of wood fixed together and attached to the upper edge of the garden’s timber frame. (These frames are now available commercially, but it is also possible to construct a similar matrix using string or recycled materials, such as strips of old Venetian blind.)
Bartholomew’s garden concept evolved over time to become raised beds divided into four by four foot squares, further divided into 16 one-foot-square spaces. Metric gardeners can use the concept of one by one metre gardens divided up into nine equally sized squares. The size of a metric garden means that all sections can be reached without the gardener having to step on the bed, thus avoiding compaction. The beds are also small enough to be easily covered with shade-cloth, frost-cloth or mesh, if required.

Square-foot gardens were originally raised using timber, but any other available material that suits (such as bricks, hay bales or woven basket willow) is acceptable. It is even possible, where perennial weeds are a problem, to line the garden with weed matting.

Bartholomew stipulated that his raised beds should be filled with a carefully prepared growing medium made from one-third peat moss (sphagnum moss), one-third vermiculite and one-third finished compost, measured by volume rather than weight. Although this fill may at first seem costly to provide, it must be remembered that Bartholomew considered a soil depth of just 20cm to be sufficient. (In the interests of sustainability, gardeners might now prefer to substitute coconut coir for peat moss.) Note: if preparing the mix yourself, wear a mask and damp down the ingredients before you work with them.

Correct planting was of the utmost importance to the success of Bartholomew’s gardens, and this is where the grids came into their own, acting as guides and making everything as simple as possible.

In square-foot gardening, each square is given over to a particular plant, and how many plants can be sown into a square depends on the variety being planted. For larger plants, such as a cauliflower or tomato plant, for instance, an entire square is devoted to one plant. Smaller plants, such as lettuce or strawberry, can be planted four to a square. Much smaller vegetables, such as carrots or spring onions, can be accommodated in greater numbers to a square. Climbing plants are grown vertically on frames around the edge of the garden in such a way that they don’t shade sun-loving plants.

Where plants require a root depth greater than the recommended 20cm, Bartholomew (who it seems had rules for everything) suggested that a small ‘topper box’ could be placed on top of the growing space to hold a deeper fill.

The square-foot gardener harvests carefully, taking care not to disturb neighbouring plants. Where possible, roots are left in place to contribute to decomposition and microbial life, and the mix is topped up with fresh material before the next planting. Rotation is of paramount importance.
Bartholomew’s gardens were not a place for tools, and the close proximity of plants to each other was said to reduce water requirements to 10 per cent of that in a row-grow garden. The diversity of planting in a small area meant that pests would, hopefully, keep their distance.

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Square-foot gardens can be raised to any convenient height

Is square-foot gardening for me?
Square-foot gardening is ideal for first-time gardeners (and children) as its rigid rules allow little room for making basic mistakes. What’s more, this type of garden can be set up in almost any kind of space – even on top of concrete. Because of their small size (even if you have more than one), tasks seem more manageable in a square-foot garden and, in fact, they are, given that close plantings mean weeding and watering are minimal.

What deters some from square-foot gardening is that it is relatively costly to set up (unless you are converting from a previous gardening style, in which case you will be able to convert at least some of your existing infrastructure).

The shallow nature of square-foot gardens also restricts what you can grow (unless you want to go to the fuss of extending a square by adding a topper box). Plus, bushier plants (such as courgettes) tend to crowd neighbouring plants.

Although square-foot gardens are said to be virtually weed-free, once weeds do appear and become established it can be difficult to remove them. This is because the garden is so densely planted that even using hand tools is almost impossible.

As with any method of gardening, there are pros and cons, and your own personal circumstances will dictate whether this method is the one for you.

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