I have outgrown the 1m2 vegie patch and am ready to invest in a building 2 new raised vegetable garden beds, and one needs to be at least 3m wide.
Here is a sketch of what I am after:
We got started on this job over the weekend, to make sure that it is ready for spring planting, especially for the tomatoes. Have been having a look at some of the corrugated galvanised beds, but decided against them and will go with a timber bed instead. The big deciding factor here was aesthetics, I really prefer the look of the timber. I also kinda like the idea of being able to perch on the edge on a timber bed and sit amongst the garden!
Have to admit, I was also a little surprised by the price of these cut-down rainwater tanks – around $250 for a medium sized unit, which is a huge mark-up on the cost of the materials used. I guess it is a trend at the moment, and the market will settle back to a reasonable price soon enough.
Another material worth considering is recycled plastic “timber”, I found a manufacturer here in Adelaide and was impressed with the quality and range of their products (link here). However, if you price it out per linear metre, the recycled plastic is about twice the price of timber.
In the end we used 2.4m lengths of hardwood sleepers, as this is a standard length and easy to find at most hardware stores. The width is 200mm and thickness is 75mm. You can also use untreated pine, or other recycled timbers.
Building it basically involved using the timber on end, and creating 2 boxes on top of each other. I was initially aiming for 600mm high (using 3 sleepers), but this was a bit too high, and I might have needed a stepladder to pick the tomatoes!
Luckily my husband is pretty handy with drills and bolts etc. so he put it all together while I made encouraging comments. The key was to get the first pieces in place, ensuring they are level. The corners were fixed with brackets, see pictures above. There is an irrigation poly pipe in place ready for drippers. The bed is filled with a soil/compost mix from Jeffries that is called “Special Soil”.
I guess the other idea I was considering is creating a frame over the top so I can hang 50% white shade cloth over the top to protect from sunburn. This is a technique used by commercial vegetable growers, with the main benefits being reduced water loss and plant stress – resulting in better yields and less crop losses. Obviously this is not necessary in all climates, but here in Adelaide we can get a whole week of temperatures over 40° that really knock the garden around.
I will do some more research on this and update the site with some technical info from commercial vegetable growers.