Our first garden was a container garden on a balcony. We had no soil, so container gardening was the way to go for us. It is fun to grow a container garden on a balcony, patio, driveway or in a greenhouse. Containers allow us to grow food without owning a speck of land. Containers are also great for indoor gardening. You can grow your own salad greens year-round, or early carrots and even tomatoes.
Container gardening also presents some challenges. There are things that are true for any container garden, and there are things that are unique to grow bags. If you have the choice to grow in good soil, it is always better than any container. But if you need or want to grow in a container, a grow bag is a great option.
Why grow in grow bags
Grow bags are made of breathable fabric which means superior drainage and aeration. It is the aeration that makes them superior to other garden containers. If a container has no aeration and the roots reach the walls of the container, they give a signal to the plant to make more roots, resulting in a root-bound plant. Eventually, the plant just kills itself with a mass of roots going round and round in the container. Here is an end of season comparison picture. Both plants are done with growing, but one is completely dead.
Root bounding will not happen in a grow bag. Here if a root reaches the wall of the bag, it will be “burned” off, causing the plant to constantly produce new and healthy branching roots. This is also called air-pruning. This picture shows nicely how the roots did reach the wall of the bag, but did not go round at all.
Soil for grow bags
Soil is the heart of any container gardening. In the grow bags we use Mel’s Mix from the All New Square Foot Gardening book. It is a great mixture for any gardening, also container gardening. The mix is 1/3 moss, 1/3 compost mixture (for example chicken manure, horse manure, and mushroom composts), and 1/3 vermiculite. This mix preserves moisture which is very important for grow bag gardening. Read more about soil for container gardening here.
We also mulch our grow bags with wood chips just like the garden. It helps to keep the soil moist on top, and we find that plants just grow better with mulch even in containers.
You can reuse this soil mixture year after year. Remove the wood chips mulch, empty all the bags, add about 10-20% new compost, and mixing it well up again.
Watering grow bags
Watering is always a challenge in container gardening. Too much makes the plants sit in water, too little makes them dry out. It also depends on what the container is made of. Grow bags do dry out much faster than pots. The drainage and aeration of the grow bag, leads to more frequent watering needs. Also, it is difficult to really soak a grow bag, the water will come right out. Two things can be helpful.
Install a drip system, so the grow bags get a constant moisture supply. We tried the bottle drip system. It did not do so well for us, even though many have great success with it. A pipe drip system would work well, too.
Self watering system
Have a container underneath the grow bag that you can fill with water so it can be wicked up. Any container would work, we got the idea from the Kiddie pool grow system. But if the container is too deep, you will need an overflow. You want most of the roots to be in air.
Here a build box out of styrofoam, it is not very deep, so an overflow is not needed. It looks like a raised bed. In this we planted cucumbers. Cucumber like water a lot.
Same idea, but boxes build out of wood and covered with plastic.
Fertilizing grow bags
Since containers do not contain much soil, heavy feeder plants need to be fertilized. Personally we prefer natural fertilizers. Bone Meal, worm casting and compost tea are all great natural fertilizers. Also, Epsom Salt and eggshells can help to add minerals.
Hope we could encourage you to grow a container garden using grow bags.