There are many sub irrigated planter (SIP) designs available – many use 2 buckets and are complicated and very tedious to build. The improved Alaska Grow Bucket needs only 1 bucket, a plastic kitchen colander, and a fabric shopping bag. Construction is easy and takes just a few minutes. I believe the Alaska Grow Buckets are the easiest self-watering planters anybody can make to grow their own food.
Connect several Alaska Grow Buckets for a complete self-watering growing system.
Several Grow Buckets can be combined in a system and connected to a bulk reservoir for automatic irrigation. A float valve regulator is used to maintain the optimal water level throughout the system. As the water is drawn up and absorbed by the plants the float will drop and open the valve replenishing the system automatically. A 35 gallon reservoir is refilled about once every week or two, depending on the number of Grow Buckets in your system. The advantage of this system over other more complex hydroponic systems is the lack of electric pumps to circulate water and nutrients and to aerate the root zone. The lack of electric pumps means that power is not necessary. You can use this system anyplace you have a water source.
The first key to this system is the growing medium. It must have a strong wicking property. Soil or compost will not work. A soilless mix with the correct properties is necessary. I prefer a commercial product called PRO-MIX BX BIOFUNGICIDE™+MYCORRHIZAE™. It consists of Canadian Sphagnum peat moss, Perlite, Vermiculite, dolomitic limestone, wetting agent, Mycorrhizae, and a BIOFUNGICIDE™ - (Bacillus pumilus). Other Peat based soilless growing mixes will also work – but the addition of perlite and dolomite lime are recommended.
The second key to this design is the readily available fabric shopping bag. These common bags can be found at most supermarkets and are very inexpensive or free. The bags are made from spun polypropylene and are very porous. To test a bag simply fill it with water. If it runs out freely then it will work. Similar “Grow Bags” are available from nursery and garden suppliers at a much higher cost. Canvas or burlap bags may also work – but they will eventually rot and fall apart. The porous fabric allows excess water drainage and aeration of the root zone which is necessary for optimal growing conditions. The system is also based on the principle of “air root pruning”. As roots grow out to the porous fabric they become exposed to air, dry out and die. This causes the plant to produce dense fine feeder roots and prevents root circling. The increase in fine feeder roots leads to better nutrient and water absorption and promotes accelerated plant growth.
The third key to this system is a plastic kitchen colander, that will hold the fabric shopping bag off of the bottom of the bucket and create a shallow water reservoir in each grow bucket. Almost any large plastic colander can be trimmed to fit inside a 5 gallon bucket with a strong pair of shears. There is one colander that will easily fit without trimming. The Arrow brand model #289 4Qt. plastic Colander fits perfectly without trimming.
The fourth key to this system is the 5 gallon support bucket with plentyof ventilation holes around the sides. The bucket helps support the fabric bag and the ventilation holes allow adequate air movement. The bucket also acts as a water reservoir below the bag providing a water source for the wicking grow medium. By maintaining the proper water level with the float valve regulator the medium will never dry out and will continuously wick moisture up to the root-zone.