04/10/2026
I heard Edible Gardens by Craig Castree discussing this recently on Let's Talk Gardening. This is something we do as well, planting dynamic accumulators like Borage and Comfrey with a few other companion / complimentary and pollinator plants like nasturtiums, camomile etc underplanted as a 'Guild'. Craig has written a good post on this, so we took the opportunity to share it.
Good morning. After running a companion planting workshop yesterday, I thought it poignant to share some of what I shared yesterday in the workshop. One of the big ones, is planting bioaccumulating plants around the drip line of either fruit trees, or particularly around citrus trees. Because in days gone by, I was taught, as were, not to plant things beneath citrus trees because they have shallow root systems and they don't like competition.
Well, over this time, I've come to realise that that's not quite correct. Yes, they do have shallow root systems, and they show deficiencies often because of that shallow root system, not able to reach some of the heavier metals, things like iron and zinc and so forth, that sink down below their reach. It's not that the soil is missing these elements; it's that the lemon tree can't reach them. They're either locked up or unavailable. So, to plant some bioaccumulating plants, that's those with long deep tap roots that can tap things like the clay table and the subsoil levels to unlock, solubilize and bring back into the topsoil profile the very things, the minerals and nutrients that the lemon tree is showing deficiencies for, make that available through the topsoil profile, through the fungal network and the microbiome of the soil, is a wonderful way of being able to minimize joining the moron club. Because in the past, I would have recommended that you go out and get yourself a bag of trace minerals and add more on the soil. After all, that's what we were taught. Through my study into soil microbiology and how the microbiome of the soil works, it's become blatantly obvious to me that we kind of misunderstood how this all works.
So, the new way forward is absolutely knock yourself out, plant beneath your lemon trees. But around the drip line, it's these bioaccumulating plants, things like comfrey and borage and even celery and potentially parsley and the like. These have deeper tap roots that are able to lift up these heavier metals and make them available to the citrus trees.
For more information, you can get a copy of my books from my website: https://craigcastree.com.au
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