A few years ago I was faced with an issue of needing to keep some seedlings warm, combined with not a lot of money to spend and limited resources. This meant being creative with what WAS available and the result is functional, cheap and reuses things that mostly would have been thrown away.
I already had an existing 4’x4′ compost bin created by putting together pallets. To this basic pallet compost bin I nailed a “ladder” framework. I then cut the bottoms off of 2 liter soda bottles, putting a hole in the cap before screwing it back on which insured water dripped out rather than pooling in the container. The bottom piece cut off – a small ‘bowl’ – I’ve used for starting seeds.
Once the framework was done and the bottles prepared the bottles were turned upside down and a small screw attached it to the frame. A larger screw was driven through the neck for solid support – I used 1-7/8″ screws but 2″ would have given a little more security. The bottles were arranged 10 across the 4′ span, with the base arranged so it funnels into the bottle below it. The bottom row drips into containers. In this way watering the top layer goes through to drip into the 2nd layer. If, in the case of rain, it is too much it continues to trickle down and finally out the containers if excessive.
Once the bottles were arranged, it’s a matter of filling them – I used a handful of broken up leaves in the bottom followed by a soil mixture. The mix is compost, soil, manure and bagged top soil. On one side there are 20 pepper plants are in these, one to a container, with ten zucchini on the top layer. The zucchini will be ‘trained’ over the top providing shade over the compost bin as well as making use of space.
The other thought to this was keeping seedlings warm in case of an unexpected cold snap. A sheet of plastic from a farm store – less than $20 – was employed to go over the entire frame. The natural heat from the compost bin provides enough to, in the south, raise the temperature just that few degrees to keep them from getting nipped by frost.
Fancier materials from new purchase can be used with the same idea but for what was needed these have worked very well. It allows up to 170 plants in a 4×4′ space. For those with limited space, such as a patio or balcony, it would be easy to adapt to allow herbs and vegetables too be grown even if you don’t have a yard or garden area.
As it was used, in direct sun the soil will get too warm and ‘cook’ the roots, so plan the location well. Yes it will fall apart in a few years – but $30 for five years is not a bad value.