Sydney Companion Planting Experiment
Updated: Mar 26
However this year, we decided to run an experiment in our larger garden bed to see if we could triple the yield with companion planting.
Read on to find out how we went planting 48 corn, 48 eggplant and 25 sweet potato slips in the same 4m x 1.5m wicking bed!
About Companion planting
Companion planting is essentially growing more than one crop in the same space. This makes better use of the space, and if done cleverly can take advantage of the available:
light - plants that are different sizes at different times can maximise light
nutrients - different plants that require different nutrient balances can happily coexist. In fact legumes can even provide nitrogen to other crops.
space - root vegetables planted with leaf or fruit based plants take advantage of above and below ground space. Vertically grown plants take little ground space
Companion Planting Considerations
In order to work well, we need to think about a few things:
Water - More plants need more water. You will likely need to water much more than with a single crop. We grow ours in self watering wicking beds so this is not an issue ( read more about wicking here... )
Nutrients - a certain amount of competition for nutrients will likely mean additional fertilisation requirement. The built in composters in our raised beds make them largely self fertilising so we have not added anything this season. (read more about self-fertilising beds here...)
Use of space - You need to ensure the plants get the light they need to flourish. Vertically grown plants, such as beans and tomatoes should not be places so as not to shade out the other plants alongside. A slow germinating or slow-growing plant should probably be put in before a faster one alongside, to allow it to get established.
Our Experiment : Corn, Eggplant and Sweet Potato
We wanted to see if we could triple the output of our 4m x 1.5m wicking bed with companion planting.
(If you are not sure what a wicking bed is, and why they are so great for prolific vegetable growth, click here to read more...)
We decided to companion plant corn, eggplant and sweet potato. The rationale was that corn is a fast growing, tall, quick producer. Whilst it is growing, the eggplant could be maturing underneath, coming into it's own once the corn was harvested. The sweet potato needs over 100 days in the ground, so would be there waiting for us at the end of the season.
First we planted the 48 eggplant straight out from seed in mid September, knowing the corn would overtake it, as eggplant seems slow to get going early.
2 weeks later we seeded 48 corn in between the eggplant. We planted in trenches to give the eggplant the light for longer, and to provide the corn with more stability as it is quite a windy spot.
Finally we planted 30 sweet potato slips, spaced between the other plants. We had started these slips in water indoors 2 months earlier, as they take a couple of months to get going.
Results So Far...
The wicking beds seem to be great for supporting all three crops at once.
We harvested around 60 corn in early December. The worms in the built in composter were certainly doing the job, as many plants produced 2 cobs instead of one, and some even produced 3!.
So far we have had 25 eggplants, with plenty more on the way. We grew a mixture of a smaller "finger" variety, and the larger ones. The taste on the larger ones seems to be far superior - not sure we will bother with the finger ones again.
The Sweet potato is absolutely taking off, but a little early to tell yield. This will be the last thing we harvest , once the eggplants have finished, so as not to disturb the roots.
We would be keen to repeat this exercise in future years, however there are a few things we would do differently.
The eggplant was a little slow to get going, as it probably prefers the weather a little warmer. It was quickly overtaken by the corn, and shaded out a little earlier than we intended. However it survived well and produced plenty. We would perhaps consider starting seedlings indoors a little earlier next time.
The corn took off quickly, and we had an excellent yield. However some of what we planted was last year's kernels we had saved as seed. They apparently were not "heirloom" varieties, so they reverted towards a south american variety that was very chewy, although still edible. Next year we will be sure to only use purchased corn seed. SelfSufficientMe has an article here about heirloom seeds (and they also have a wonderful YouTube channel for the Australian climate here)
We did get some interference with the corn cobs from "Ear Worm". However we learned a natural and effective treatment to be timed after pollination using neem oil. If we started eggplant earlier in future years, we would need to time the corn treatment for before the eggplant blossoms so as not to harm bees. As usual no issues from slugs or snails in our wicking beds, as they hate the dry soil surface. More on that here...
Companion planting has worked extremely well for us, although we were glad of the self-watering, self-fertilising and self-weeding aspects of our raised beds. We look forward to continuing the eggplant harvest and seeing the sweet potato yields.
Have you tried some effective companion planting combinations? Let us know in the comments.
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