Small-space gardening is becoming increasingly popular as outdoor spaces and gardens get progressively smaller in urban areas. There are many ways to maximise the use of limited available space, and one of the best ways is vertical gardening, growing upwards rather than outwards!
Gardeners are very resourceful, and in the gardening world there are many techniques which have been developed to take advantage of vertical spaces, such as espaliered trees grown flat against walls, even more compact columnar ‘cordon’ tree forms, and methods which rely on structures such as trellises and arbours.
Some of the best vertical gardening solutions can be so deceptively simple that it’s often overlooked! One of the least appreciated ways of growing edible climbers is over an arch, mainly because people don’t realize how much growing space is available on a relatively small archway.
How Much Growing Space Can Arches Provide?
An arch at first glances would appear to offer very little growing space. How much growing area can a small 1m (3’) wide x 2.5m (8’) high arch, a little taller than a house doorway, actually provide? If we do the math, we might be in for a bit of a shock.
Most people ignored maths at school, and glossed over geometry. Where will I ever use this stuff? Well, life is full of surprises…
To calculate the total length of an arch, we can simply use a tape measure, but when was the last time anyone did that? Arches are often dismissed as being small and insignificant, and without first considering the value of arches, there is no inclination to seek them out for measurement!
Calculations are useful for design purposes, we can use them to work out the size of an arch required to support a certain length of edible vine such as a grape of berry, or we can determine how much growing space an arch of a given size can provide.
The short answer:
The formula for calculating the total length of an arch = (2 x length of vertical side sections) + (3.14 x 0.5 x width of arch)
The diagram below shows how an arch consists of two main sections, the pair of vertical sections at the sides, and the curved section at the top, and how their lengths are used in the calculation.
If we use the earlier example of a small 1m (3’) wide x 2.5m (8’) high arch and put these figures into the formula:
- total length of an arch = (2 x length of vertical side sections) + (3.14 x 0.5 x width of arch)
- total length of arch = (2 x 2m) + (3.14 x 0.5 x 0.5m)
- total length of arch = (4m) + (1.57m) = 5.57m
What this tells us is that an arch not much larger than a house doorway can support a vine over 5m long, and it only occupies a very small area on the ground where the vine is planted, which can be as little as 50cm x 50cm (around 20” x 20”). That’s a very efficient use of space!
The long (and possibly unnecessary) mathematical explanation:
How was the formula above derived? This is for those curious about the maths, otherwise just skip this section!
An arch consists of two main sections, the vertical sections at the sides and the curved section at the top. To calculate the total length of growing space of a garden arch, we need to add the length of the vertical sections at the sides to the length of the curved semicircular top section.
- The length of the vertical side sections are known.
- The length of the curved portion can be calculated using the formula for the circumference of a circle (the length around a circle).
To explain how the formula given earlier was derived mathematically:
- For a whole circle, the length of the circumference: C = 2π x r , where π = 22/7 or approx. 3.14, and r is the circle radius (half the width)
- For a half circle, we halve the formula: length = 2π x r x 1/2 = π x r = 3.14 x r
- Since the radius is half the width of the arch, the simplified formula therefore can be expressed as:
total length of an arch = (2 x length of vertical side sections) + (3.14 x 0.5 x width of arch)
Permaculture Small Space Intensive Gardening Using Arches
The Permaculture design principle known as the ‘Edge Effect’ is concerned with the use of edge and natural patterns for best effect. In Nature we see extensive use of folding to maximise functional area in a small space. The human intestines, both in terms of their outer form and the structure of their internal surfaces for the absorption of nutrients, are both a perfect example of this.
Now consider how long a 5m (15’) long vine really is, that’s quite a decent productive length of vine by anyone’s books, and a trellis this long to support it would occupy a considerable amount of space. If we do what Nature does and fold the support structure in half into the shape of an arch, the growing space ends up concentrated into a much smaller area no bigger than a doorway.
If the arch is situated to span across a path, it converts unused walkway into growing space without obstructing access. A free standing arch in a garden multiplies space, as the the area underneath the arch can also be planted up, creating a double-level planting.
The photograph at the start of this article is of a loganberry arch in my backyard Permaculture food forest garden, which has proven to be extremely productive. This arch sits over a path, one side sits in the garden, the other beside the back fence. The arch is quite narrow, only around 30cm (1’) wide, and I train around 6-8 canes over it, and allow them to grow right over the arch, where they reach the fence. I then run the canes along the fence for an extra metre or two.
Considering that this loganberry arch has 6-8 fruiting canes, each around 5-7m long, is it any surprise that it’s extremely productive? The loganberry only occupies a very small area in the actual garden bed, the footprint is minimal, approximately 30cm x 60cm, around two square feet, yet it supports a total of 30m-56m (98’-183’) of productive canes.
The same loganberry vine is pictured below, during harvesting time. It’s no exaggeration that people have picked enough berries to fill bags and the plant looked untouched due to the very heavy cropping. Daily harvesting becomes necessary with this much production. To protect the berries from birds, it’s easy to toss a length on 2mm insect exclusion netting over the arch, the fine mesh doesn’t get tangled on the brambleberry thorns and also provides 20% shade for the berries during hot, windy weather, preventing them from over-ripening and burning.
Garden Arch Construction
My loganberry arch was just a cheap pre-fabricated unit from a garden store which you assemble, and was given to me by a friend who didn’t want it. It lasted around 8 years, which is not too bad. Proper commercial garden arches are usually constructed of more durable materials and will last forever. They come either as a single structure or as two pieces that are fastened together.
It’s possible to build your own arches from a variety of construction materials. A popular construction method is to a fasten rebar mesh sheet bent into an upside-down U-shape to the ground with steel posts. The mesh sheet is tied to the posts with heavy galvanised wire, or you can use U-bolts, which are used to fasten posts together.
If rebar sheets are not large enough for an arch, or can’t bend enough, two sheets can be used, one for each side, and fastened to each other at one end with some overlap using U-bolts.
The picture below is an arch at a community garden constructed with rebar mesh (which is used to reinforce concrete slabs) held in place using star pickets or droppers.
I often get questions about what a star picket is, so I’ve included a picture of one below. They’re very sturdy steel fencing posts that are also called Y-posts of droppers, one end is flat, the other is pointed, with holes along one edge to tie wire through. Any sturdy, long-lasting post can be used, and I believe the US equivalent is a T-post which is used for fencing.
A rebar mesh sheet can also be fastened vertically to create a support wall for brambleberries to climb up, and that’s what was done at the same community garden, as pictured below.
Small Arches for Extra Growing Space Over Garden Beds
For extra growing space over raised garden beds, it’s possible to construct small arches for running climbing vegetables over.
A 1.6m long reinforcing mesh arch will span a 1m wide bed, and sit only 50cm high. That’s a lot of additional growing space for such a small structure.
Arches are a simple way to increase vertical growing space, they work very well for all brambleberries (loganberries, boysenberries, blackberries, etc) and can also be used for grapevines, kiwiberries, indeterminate (vining) tomatoes, climbing beans and peas and many other vigorous edible plants which require supports to climb on. A gardener is only limited by their creativity!
This article is great timing for us, thanks. We just yesterday were deciding where to make an archway from a sheet of reinforcement mesh as support for both pumpkins and beans this season.
It’s amazing how much growing space this will provide
The narrow reinforcement mesh strips are a great material to construct arches from. It was only when I had to measure up the materials to construct an arch that I became aware of how much growing space they really provide!
Yes! Trench mesh – we have an archway made up of 4 of those connected with one laying along the tops over our 6 metre long raspberry patch.
This works well to throw netting over at fruiting time
Very interesting, thanks. Assuming reinforcement mesh is for ferro-concrete: what specs (wire thickness) do you prefer for e.g. pumpkins? Also: your arch is as you say 5.57m allowing a 1m wide walkway underneath. So an uncut panel has to be 5.57m in one dimension. But if I want an arch/arbour 6m long with 2.5m headspace and a 1m walkway by the 5,57m you mention that is over 30 sqm of mesh.
What sort of supplier has that, I don’t know that Bunnings has?
Secondly: are star droppers buried 300mm down and zip ties enough or do you use concrete footings?
Hi Elendur, my apologies, I’m afraid I’m not following the maths here.
In Australia a reinforcing mesh standard sheet size 6m (length) x 2.4m (width) = 14.4m2. It’s fairly wide for an arch, and could be cut lengthwise to produce two 1.2m wide arches.
All landscape supplies stores sell reo mesh, and you can also get the narrower trench mesh strips which are 6m long and 20cm wide.
The star pickets can be hammered in the ground, the correct depth is 60cm deep, if the soil is loose then you can dig a hole, place the posts in, fill with gravel and then pack the gravel down hard. You can use concrete, but I wouldn’t bother in the garden, it’s too permanent if you want to change things later! Just use 2mm galvanised wire to attach the mesh to the holes in the post, zip ties or cable ties aren’t strong enough. The other option is galvanised U-bolts.
Pumpkins are fairly light, the arch doesn’t need too much structural strength at all, unlike grapevines and kiwifruit vines which can become extremely heavy and pull a weak fence down.
If I may add my 2cents – We’ve recently erected a reo mesh archway for beans and pumpkins and bought the F52 (thinnest gauge) from our local Home Hardware.
If I did it again, I would use the F62 or F72 for a more rigid structure.
We used star stakes and wire as Angelo has described in the reply to you.
If you want your arbour to be 6 metres long, you would need 2 full sheets of mesh plus 3 lengths of trench mesh (which is available at 400mm wide, as well as the 200mm that Angelo mentioned)
[2 at 2400mm plus 3 at 400mm = 6000mm (6 metres)]
[the 5.57m in Angelo’s maths really is close enough to the 6m of a reo panel that the height of 2.5m won’t be affected in any substantial way]
@Angelo and Carol: thanks for the info, much appreciated
Could I ask, does the reo bend that easily to form an arch?
This is great! I hope to build a couple as soon as I can leave the house (Covid 19). I have several questions. First, Im from the US so not familiar with the terminology. If anyone knows the terms we use here, what are star pickets or droppers? Are they the same as T posts? Second, what material is used to frame the arch? Is it what we call rebar? If so, how is it bent (same question as Ellen) and how do you get consistent curves? Or does it bend on its own as it gets attached to the posts on each side? That would seem to require considerable strength unless I were to use very thin rebar that easily bends. If that wouldnt be strong enough, is there an alternative material for forming the arches? Third, Id like to grow butternut squash which is both rampant and heavy. Will this design hold it up, especially if I keep training it back to the trellis?
Hi Alex, thanks for your question, you got me to update the article with more useful information, I’ve added a new section on garden arch construction, discussed the metal posts and added a picture of huge pumpkin plants growing over a rebar mesh arch. With the rebar sheet, depending on the thickness of the steel rod, if you hold it at each end and move the two ends towards each other, a gentle curve will form. If there’s not enough give in the material, you may need to overlap the ends of two sheets, and join them together with galvanized U-bolts to create a longer sheet, the extra length will have more flex and allow you to create a U-shape.
Thank you for this information – in all my searching on how to make arches, this is the only article that gave specifics for this urban construction novice on what the grid material is, where to find it, what sizes, how to use it. Just one question left – any ideas on how i get it home on a small city hatchback car??? –