Angus StewartDeep planting – horticultural heresy?!

Planting depth has always been a very simple concept in gardening and horticulture. You simply put the plant in at the depth as it was in its pot and you can’t go wrong. Planting any deeper is heresy, because it will die very quickly from root rot or collar rot. This has always been the conventional wisdom, that I, myself, have spread for many years.

Using a post-hole digger to create a deep planting hole

However, I did a story a couple of years ago for Gardening Australia on a subject called long stem planting, where plants were put in up to a metre deep. You get some long tubestock, a deep hole is drilled and you virtually just bury the plant alive, up to a metre deep. It seems like horticultural heresy, but my experience with this technique suggests that it does really work.

The long stemmed planting technique can be found on the internet. If you search for “Bill Hicks” and “long-stem planting” you’ll find a

Working down further to make the deep planting hole

whole lot of research that this very dedicated environmentalist has done on this technique. It’s something he pioneered, as a technique for stabilising river banks, in the Hunter Valley in particular. Being concerned about the use of willow trees to stabilise river banks, and then those willow trees going feral, Bill Hicks posed the question, “why not use indigenous native plants?” He was told that they would wash away in the first flood on those river banks so he suggested planting them a bit deeper. This idea met with all the usual objections, but over a 20 year period, Bill has been planting things up to a metre deep and the results have been nothing short of astonishing. Not only to the majority of plants put in much deeper survive, but they actually thrive, growing at a faster rate and they are also much more stable.

Dropping the long-stemmed Melaleuca down the hole – note most of the stem is now buried

Now why would it be that planting things much deeper than normal gives a much better result? A few points have arisen out of Bill Hick’s work.

1. When you plant more deeply, the rootball of the new transplanted potted plant goes in at a level that’s better insulated from the soil surface. The rootball is usually in the top few centimetres of the soil, and if that dries out, the whole plant is at risk unless you can water it regularly. If it’s planted more deeply, it’s down in the subsoil, insulated, so it doesn’t dry out as readily.

2. It’s apparent from research that most plants that are planted deeply have the capacity to form a new root system along the buried stem, giving it a big advantage in terms of being able to access water and nutrients from a much greater depth in the soil profile.

Watering the new planting in. Only the smaller top stems are above ground level, and the main stem is completely buried.

I have personally observed many planted trees that were deep planted perform better.

Are there any exceptions to the deep planting rule? Anything with a clumping habit is excluded, like an agapanthus or a dianella, that has its growing points at ground level; if they’re planted a metre deep they’d never make it to the top! But anything that has an elongated stem, and especially plants that strike well from cuttings, it’s possible. Over the past two years I’ve experimented with this technique, and I’ve found it to work for a very wide range of plants, both native and exotic.

A few months on, and the Melaleuca shows rapid growth

I’d like you to take some small plants home that you could afford to lose, and do a little experiment at your place with deep planting. The plants don’t have to be a metre long to be successful like Bill Hick’s long-stem planting, as that’s a more specialised thing for erosion control, where obviously the deeper the root system the better. But in the garden I’ve found that taking a plant that’s 10 or 15 centimetres high and planting it so that 70% or so is below ground level, does give you tremendous growth advantages.

To summarise, deep planting works because the plants establish better and over time they form a much more extensive root system that gives the new plants a competitive advantage.

The Melalueca is quickly blending in with other established plants

There are a couple of conditions:

1. The stems do need to be elongated and the more easily they form adventitious roots like when they’re struck from cuttings, the better result you’ll get with that species.

2. The other important thing is oxygen in the soil. If you have a very heavy clay soil that’s constantly waterlogged then I’d be wary of using the deep planting technique.

So – have a go! And please let me know about your experiments with deep planting – both your successes and failures!

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Angus Stewart

About Angus Stewart

Gardening Australia TV presenter, author of 'Creating an Australian Garden', 'Australian Plants for Year-round Colour' and 'Let's Propagate', garden travel guide, native plant specialist and breeder. Central Coast, NSW. Find out lots more about native plants at Gardening with Angus.

5 thoughts on “Deep planting – horticultural heresy?!

  1. We are having a discussion about the suitability of this technique at Treeforce in Cairns. We do still have drying out concerns here in the wet tropics, believe it or not. Also, the deep planting gives the opportunity to leave a portion of the planting hole unfilled, giving a better reservoir than the traditional dish method.

    I am still wary, but may have to concede its worth a go. We will give it a try.

    • Hi Boyd,
      I understand your reticence as it flies in the face of a lot of established theory. However, I have trialled it a lot myself and have largely been successful but there have been failures as well. My rules of thumb for it to work well are that the soil should have reasonable drainage and the root system should not be out into waterlogged conditions at the bottom of the hole. Also if you try initially with plants that can be propagated by cuttings then you already know that the plant is capable of forming new roots on the buried stem. Try it with a few plants under your conditions to satisfy yourself before you do any mass plantings.
      Best regards

  2. Hi Angus,

    I have several Australian Red Cedars that I have nurtured in pots for about 4 years or so since buying them as seedlings. They are now about 1.5 metres high in 50cm pots. I am ready to plant them out in our Sydney garden. I like the idea of deep planting as it makes a lot of sense, but I am not sure if this would still be valid for this size plant rather than tube stock.

    Is it likely to still be a valid method for these older plants?

  3. Hi Angus have you tried this technique with fruit trees. Ive got some olives and citrus in pots that i want to plant and am thinking of trying deep planting. Im in perth so have plenty of free draining soil.

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