Multi Tiered Wooden Garden Vegetable Planter

The Problem

I had been trying to grow vegetables for a number of years with moderate success in various beds that were in place when we had bought the house. I did a bit of research and decided that it must be a lack of sunlight that was causing the issues. Non of the existing beds had direct sunlight for more than half a day.

The Solution

I went in search of a better location, eventually finding a patch of lawn that had nearly uninterrupted sunlight from dawn to dusk. I've made a few raised beds previously but as this was in view of the front of the house I wanted something a bit fancier and that would last.

Potential Issues

At the time of writing timber is somewhat difficult to get hold of and prices are through the roof so I took a few hours to make a full Sketchup model of the bed in order to make best use of the timber and minimise wastage as much as possible.

The Finished Design

The shape, size of the finished bed will need to be tailored to suit your location and the material you can get. I managed to size it so that each layer of the Hexagon was made from nearly two complete lengths of timber and each layer of the tiered bed was made from full and half lengths. The entire area of the build is on a slight slope, which lends itself nicely to the tiered design.

On additional thing to note is that although I really like the look of the bed, the two internal corners where the Hexagon join the straight section are really difficult to mow, in fact the entire bed makes mowing the lawn a much more arduous process entirely but everything has a cost :-)

Materials

• Timber - I designed the bed to use one size of timber, in this case Incised Timber Fence Posts 75 x 75mm x 2.7m. There are a few things to bear in mind when choosing the timber;
  • What is available to you and its cost.
  • Wastage, I chose the lengths specifically so I could use mostly whole or half lengths
  • Tool capacity, a 75mm fence post is easier to cut through than a 100mm
  • A trade off between size and longevity, a bed made for bigger timbers will last longer, but will take up more space or have less soil capacity.
  • Treated or untreated, again treated will last longer but some folks don't like to use treated timber around food
• Screws
  • 6mm x 200mm (for the angled joints) These need to be longer as there is more material to get through when drilling at and angle.
  • 5mm x 125mm (for the all other joints)
• Wood treatment, as the design includes exposed cut ends, these need to be treated if you wish.

Tools

• Mitre Saw - I used a sliding mitre saw with a 210mm blade but even then it was only able to cut 99% of the way through the timber, another good reason for choosing the 75mm post size, as my saw wouldn't have cut through a 100mm post. You could also achieve the same with a handsaw and plenty of manual effort.
• An impact driver - I find an impact driver to be a far superior tool for inserting screws. Even against a similarly capable drill driver, I find that the impact action keeps the driver bit seated in the head and I don't have issues with the bit slipping in the head.
• A drill - I chose to pre-drill some of the screw holes to minimise the chance of splitting the ends on the timber with the bigger screws.
• A spade
• [Optional] I wanted to have rounded over edges and as I couldn't get the timber delivered with this already done, I used a router with a round over bit.

I chose to start with the Hexagonal section as this would be the centrepiece and act as a foundation for the rest of the bed to build from. To get the finished size, each of the 6 pieces needed to 750mm long with a 30 degree cut. I fixed a long strip of wood to the mitre saw and clamped a stop block in place so each of the 24 hexagon sections would be identical to the first. Once I had the first 6 cut, I laid them out to confirm that I was happy with the size before continuing.

Cutting timber of this size with at the absolute limit of the mitre saw I was using, each cut left a slight sliver of wood connected but this was easy enough to break or cut.

I chose a butt joint so that each layer could be alternately overlapped which should leave a strong finished item once the 4 layers are assembled. If a mitre joint was used, it would avoid showing exposed end grain but all the joints for each of the layers would be in line at the corners.

To assist with aligning each corner, I clamped an off cut which helped to hold the joint in position to stop it sliding before the screw was inserted. I'm not sure it was necessary but I opted to pre drill a pilot hole about 50-75mm deep to avoid any risk of splitting the wood.

I chose to additionally tread the exposed ends of the timbers as cutting them exposes untreated wood.

As an optional addition, I wanted a rounded edge to the timbers. This removes sharp edges which can't split or splinter and also emphasises the individual timbers the bed is made from. You may be able to buy the timber with this already done but for cost reasons, I didn't.

I used a string line to assist in laying out the planter relative to the existing path. This was also the first time I got to see what the finished bed may look like. I chose to position the long straight section of the bed parallel to the path with an inch or so gap with the main hexagonal section extending into the main lawn at the front of the house.

I knew the area had a general slope which I had measured and allowed for in the design and now it was time to tackle it in reality.

Once the first Hexagon layer was assembled, I used a spirit level and offcuts of wood to level the first layer and decide how deep to bury the other side. I wanted to bury as little as possible of the structure, but without exposing the base anywhere and ruining the illusion that it doesn't extend deeper down into the ground.

Once the Hexagon was set at its level I began to lay out the rest of the bed and check that the levels that I measured and made the model from were correct. I wanted to align the layers with the hexagonal section but also it was a trade off of burying as little timber as possible whilst also getting a nice even fall that fits in with the natural contours of the lawn & path. I mocked up a few different options on the computer but eventually concluded that 4 even sections looked best, this also made a very good use of the timber, with little waste. I was also able to stagger the joints in the timber, making the structure stronger overall.

Next step was to start to assemble the main tiered bed. Each 2.7 metre length of timber gave one full length and one cross piece or two half lengths and one cross member. I chose to use two lengths of cross members, one to fit inside and one to fit across the full width, I thought this fitted quite nicely with the exposed end grain to match the Hexagon. Staggering the joints like this will also give a much stronger structure.

As you can see here I'm working on the patio at this point due to the weather, I was doing all the cutting and routing in the garage and assembly outside. I was also doing what I could to keep the as yet unused timber as dry as possible because working with wet timber is no fun, no fun at all :-(

I assembled in sections and when these were done, I carried them to where the bed was installed. Normally I would've just waited out the weather but the topsoil delivery had come much sooner than expected and was quickly killing a patch of the lawn so I wanted to get the bed finished as soon as possible.

Once the full length of the tiered bed was assembled, I used off cuts of wood and a spirit level to level the bed and work out where and how much needed to be dug away to align it level with the Hexagon.

In hindsight if I was to do the job again, I would avoid having to lift the bed up to dig the soil out under. I thought I was saving myself time & effort by digging out only what I thought I needed but in reality I was doing the exact opposite. By using string lines and a tape measure, I could have worked out exactly where I need to dig.

I did originally consider building the two parts of the bed as one, but in the end I decided two sections was better and even then I could only just move and lift each part. I used two off cuts to fix both sections of the bed together to make sure they don't move out of alignment.

I had calculated that the bed should require just under one single bulk bag which should contain approximately 1 cubic metre. I was a bit unsure about the exact quantity in the bag and also how much it would compact. I committed to ordering one bag and sat back to constantly second guess myself and with I had ordered two! Looking at the size of the bag next to the bed once it arrived I wasn't feeling particularly confident.

As for calculating it, it was simple length x width x (approximate) depth of each section + the hexagon. There are plenty of tools online to calculate the area of hexagon, which you then just need to multiply by the depth.

Now was the time to find out if I calculated correctly! Turns luckily I got it right and just have enough left over to top up the bed once the soil had settled.

In hindsight, when it came to planting, I wish I had dug over the lawn underneath as in some of the shallower bed this made it a big more difficult in some places when it came to planting.

I didn't have to wait long to get some help with the the soil settling as the rain started almost immediately once the bed was full and came down heavily, you can see from the picture how much the soil in the bed sank, particularly in the corners. I waited for it to dry slightly and topped the bed up with the remaining top soil.

I had some peas & tomatoes ready to be planted which I put it straight away although I wouldn't recommend following my advice for planting as I'm still figuring that out for myself!

My eventual plan is to have a feature plant in the centre of the hexagon that will give some life all year round and then supplement with the vegetables in the appropriate season. For this year it will be all vegetables.

A month or so later and various different plants were taking full advantage of their new sunny homes, bit of an unforeseen consequence was that the the canes I had previously were now far to small and some of the peas and tomatoes had started to fall over, but that is an easy fix.

In the later set of pictures the sunflowers had really come on (possibly shading the carrots but time will tell) and after giving a decent harvest for two people every two days for nearly two months, the peas had succumbed to what I think (and hope wasn't) was wilt.

Happy Gardening.