Simply speaking, growing with the right soil is key to immediate and long term SIP garden success. For a self-watering garden, soil structure is just as important as the soil nutrients. To maximize the wicking action, and enjoy self-watering success for years to come, follow these guidelines:
Finding & Mixing the right Soil for your Self-Watering SIP Garden.
For self-watering success, soil structure is key! Standard top soil is not recommended. You need a blend ideal for wicking - loose, friable and porous like a sponge. The right structure creates an environment for upwards capillary draw, while also allowing for strong aeration to the roots of your plants.
Container Mix vs Custom Blend
Generally speaking, any high quality organic peat or coconut coir based potting mix will work. These blends can often be found locally at your local nursery, plant supply, or landscape supply stores and are very convenient. Be aware though, some container mixes with not provide the nutrients you need, and may require additional amendment/fertilization. To ensure you've got a good blend, look for the following ingredients:
Peat Moss or Coconut Coir.
Generally speaking, these two ingredients can be used interchangeably. They provide excellent water retention, while maintaining soil bulk and friability. This ingredient will comprise the bulk your soil blend.
Perlite or Vermiculite.
Used for drainage and aeration, these ingredients are both inert - meaning that they do not break down, affect soil ph levels, nor offer any nutrient value. Perlite is far more common in pre-made blends, as it is less expensive and more widely available. Perlite functions for drainage and aeration only, whereas Vermiculite improves drainage and aeration, while also being water absorbent and is excellent for regulating soil moisture levels! Some of the best soil blends use Vermiculite for this reason, as it's the ultimate ingredient for maintaining a friable soil year after year.
Vermiculite is also a great ingredient for using as the wicking agent directly in your SIPs.
Organic compost and worm castings.
The right compost is like magic for your garden, with the act of composting being as much of an art form as it is a science. If you are serious and passionate about growing your own food - finding a local organic farmer that sells their compost, cultivating that relationship will be time very well spent!
If you just want to get growing right now, no problem! Variety is what you're after. Build your soil using compost from as many different sources as possible to ensure a well balanced final product. Well rotted farm animal manure, composted food scraps, composted kelp and seaweed, and worm castings are all excellent sources of nutrients for your garden.
Custom Soil Blends:
If you’re uncertain of what's locally available, or want to mix your own, try one of the following blends. In both cases, consider adding an appropriate amount of balanced organic granular fertilize to ensure you've got a full range of micro and macro nutrients.
- 1 part vermiculite
- 2 parts organic compost
- 3 parts peat moss / coconut coir
- 1 part perlite
- 5 parts organic compost
- 10 parts peat moss / coir
Installing the Soil
But first - What goes in the SIPs?
The fact is, you can use any number of materials to act as the wicking agent to draw water from the reservoir below up into the soil above. The easiest material to use is simply your Soil - given that you've followed the guidelines above, this will work just fine.
However - if you want a longer lasting material that won't wash away over time, consider using pure horticultural vermiculite. As noted above, it has excellent water retention, is entirely inert, and won't break down over time - this make's it an ideal material to use in your SIPs.
Once the SIPs are filled up, go ahead and dump the soil in! The most important step here, is that you want to make sure that the soil is going in evenly moist. Dry soil is hydophobic and resists getting wet - putting a damper on the self-watering/wicking function of your SIP Garden. But if you moisten the soil as you install, you'll jump start the capillary for self-watering success!
Learn more about Watering here
Learn more about Fertilization and Soil health here.