Square Metre Gardening or SMG for short

I know I have touched briefly on this subject before when describing the set-up of my own garden but the more I do it, the more I feel it is worthy to share! Square Metre Gardening is the bomb! I will give a summary of the where, what, and how, here but you really need to get his book for the finer detail if you are going to do this. If I tried to write it all out here…..well, er…..it would be a book!  This book really does have everything you need to know but is sadly out-of-print at the moment.

I first came across Square Metre Gardening or SMG in the book by Mel Bartholomew. The method is also known as Square Foot Gardening. Mel described how he usually illustrated his point when giving a talk on the subject.

“How much ground do you need to feed a  family?” he asks, then divides the room in half, and half again and half again.

Whatever ground you think would need to grow veg for your family and more, with SMG you will only need roughly 20%. In other words, a traditional kitchen garden needs about 40 square metres to grow enough food for a family of four. But with an SMG system in place you would only need 20% of the space or 1/5th of the ground.

How does SMG work?

The principle of Square Metre Gardening is to grow what you need. You grow on a successional planting and harvesting basis, inter-planting when and where possible. This is achieved using square metre raised boxes, (for square-foot beds use 1 yard). The boxes can be as high as you like, mine are 50cms high but 15cms is fine. Each box frame is then divided into 9 equal squares so you no longer plant in rows but squares.

The saying:-

One for the blackbird. One for the mouse. One for the rabbit. And one for the house 

          is a charming ditty prompting the amount of seed to sow. But with the intense planting of SMG, you only plant what you will actually need. Sowing and harvesting through the season means continual harvest for as long as your growing season allows. It avoids the gluts and the burden of what to do with all those veggies, when everyone else is groaning under their harvest too! Square Metre gardening is also a “No digging needed” system. You never have to dig the ground, not to set it up, not even each year.  You continually top up the growing medium each time you harvest, giving your veggies a nice fluffy bed to grow in!

What you need to do

It does take a bit of time and effort to set up your productive garden. However using this method will save time in the long run. In his book Mel Bartholomew gives the example of a family of four needing approx. 1 square metre of salad each person. The same area each is needed for Supper vegetables. If they want vegetables for preserving, another square metre box will be required. Or if you prefer, 3 x 1 metre box of salads will feed a family of four for the season.

To work out what we would need for us here at Dovewood, I wrote down all the vegetables (and fruit) I wanted to grow. I then calculated roughly how much I think we use in a year. This wasn’t difficult as one of us doesn’t like salads or many varieties of veg.

Using the charts within Mel’s book I checked how many plants I could get in each square within the box. I also worked out what the likely harvest would be from each plant. From this I was able to calculate how many plants I would need to grow to achieve the harvest I want. For example, we use one head of cauliflower every couple of weeks so 52 weeks ÷ 2 = 26 plants would be needed. I then discovered there is a  variety that produces 4 small heads per plant. As you need one square (30cms) per plant I am planting 6 squares which should give me 24 heads of Cauliflower.

I hope that doesn’t sound too complicated because it really isn’t. Once you’ve done this bit it makes setting up your boxes so much easier. Unless there are any household changes, the plan should roll from one year to the next. The only adjustments needed will be if the anticipated harvest quantities aren’t quite right!

Potatoes can take up a fair amount of space. You could grow them in sacks rather than take up valuable bed space and you can read about how to plant them up HERE 

Creating your SMG Beds

To actually building your beds, there are kits available. You can build your own raised beds out of whatever material you have to hand or can buy. The book gives clear instructions on how to make a timber bed. One word of warning though, if you use treated wood as we have done here, you will need to line the beds. We used surplus pond liner on the inside of ours. This will prevent any chemicals leaching into the compost and ultimately into the vegetables.

The only available ground at Dovewood is a rather narrow strip. This meant adjusting the shape of the beds to suit. We have two beds approx. 2.4 metres long and 1.2 metres wide. Yes, I know, not one-metre-square-boxes but such is life! The important thing is I can divide them up into squares and apply the principle of SMG. To make them aesthetically pleasing, the opposing end of each bed nearest the central path is split level. It can be seen from the lawn and leads to a focal point of the garden. I plant these up with companion planting such as Calendula – Marigolds

What Growing Medium Should You Use?

Once you have built your beds, the next task is to fill them with compost/growing medium. Mel Bartholomew is very specific about this – any old soil just won’t do. As you will be planting crops closely, your precious plants will need to be growing in good healthy stuff. Remember no rows, no conventional spacing! He gives his “MelMix recipe” in his book the formula of which is

1/3 Garden compost

1/3 Peat Moss or Coir

1/3 Vermiculite

NOTE if you haven’t any garden compost available buy bags of general purpose compost. Buy it from several suppliers to get a good range of compost material.

Shock horror at the mention of Peat? Well this is a one-off time to buy in and you can get some from a company that harvests peat from drain water. If your conscience doesn’t allow any Peat, then use Coir – as I have – it makes an excellent alternative.

Vermiculite is preferable but you can use Perlite. It doesn’t look as nice though, with all those white blobs in the soil.

After the initial set up, all you will need is home-made compost. Each time you harvest a ‘square’ you add back a spoonful of compost to replenish the plot with nutrients. Easy!

A Difference of opinion!

Mel helpfully explains how to work out the quantities of each compost component that you will need for each Square Metre Garden bed.

There is one point I do disagree with him.

If you are making the beds deep like ours Mr Bartholomew suggests filling the base up with gravel! Aargh! No Way! Mel’s Mix is quite free draining. Putting 15cms of compost over the top would be like putting it in a sieve, all the water will drain straight through! Possibly just wash down into the gravel! If you want to grow full length carrots or parsnips you need greater depth than 15cms. They hate stony soil. If you must use gravel to fill up the base of a deep bed cover it with a membrane. Alternatively use a water-retentive material punctured with some drain holes to prevent water logging. This will retain the growing medium when it needs to be deeper than 15cms for deep growing vegetables.

To fill our raised beds

We opted for using some spare top soil for the lower half of each of our beds, and used the Mel Mix for the top half. I admit this was quite expensive as we used:-

700 litres of Coir (10 x 70lt Bricks of compressed and dehydrated Coir which we then soaked – one brick to a wheelbarrow full of water!)

10 x 70 litre bags of general purpose compost bought from three different suppliers

600 litres of Horticultural Vermiculite which I bought on eBay

The best way to mix these is to tip them onto a large plastic sheet, or as we did, onto a tarpaulin. Only mix as much as you can handle in one go. I did it by scuffing up and down in my wellies – which has to be the best work-out ever!

Once the beds were filled and levelled, my husband made a grid of timber using Roofing lathes. You could use anything to make the dividers such as: String and drawing pins, curtain rods, or metal poles. The important thing is to divide your boxes up. This is really helpful when it comes to planting the individual squares as you can actually see them. It also creates a conversation starter when showing friends around your new kitchen garden!

Planting time – help is at hand

This is the really fun part when you finally get to start your crops. You’ve bought the seed,  you’ve got your baby plants, you head to the garden and……

If you are anything like me you can’t remember how many plants go in each square! The planting distances on the seed packets usually only have the traditional spacings written on them. You will need to look each variety up. But if you are a veg growing newbie how are you going to remember that cauliflowers belong to the Brassica family or which family will you find sweetcorn in? Sorry Mel, you’ve lost me there! We need a quick planting reference…….

Planting Distances

To solve this problem, I have made a Veg Planting Distances cheat sheet which I have laminated and I take it into the garden each time I am planting. For ease of use it is arranged alphabetically, by the common names of each vegetable, (rather than by plant family names), and has the number of plants per square alongside. Such a help.   Sorry – this is no longer available