A Dry Summer? Not Your Biggest Challenge Pt 2

And so to questions of soil fertility…

My training as a horticulturist led me to believe that my capability as a gardener would be measured by the extent I was aware of, and could provide, the optimum conditions for all plants I grew.  Optimum performance was the goal.

All this is changing.

There’s a growing school of thought amongst cutting edge planting designers that stress can be worked to the designer’s advantage, and even that it can be actually beneficial to build controlled stress-factors into a planting system.

Planting by Bettina Jaugstetter in Germany, in which ‘engineered’ soil of extremely low nutrient value was chosen to deliberately limit competition amongst plants

It has been clearly demonstrated, for instance, when working with perennials in a naturalistic perennial planting, that mild and/or controlled stress factors can stabilise a planting by curtailing the dominance of individually competitive species.  This dominance is an almost inevitable outcome for long-lived perennial plantings, but planting designers have found that minimising either water or nutrient levels can create what amounts to a more level playing field of conditions, thus maximising the amount of time between corrections needed when one or two species start to dominate a planting.

The consequence is a kind of calculated ‘underperformance’ of plants in a scheme, in which the goal is acceptable, rather than optimal, performance, in the interest of planting longevity.

My ‘steppe’ garden (hmm.. I now recognise this as something of a misnomer) in which I planted into subsoil, then mulched with gravel

While this ‘stabilisation’ effect has only been demonstrated (so far, to my knowledge) in perennial plantings, woody plants from drier climates, and particularly Mediterranean climates, often grow exceptionally fast (and often very sparse and leggy) in well-fed conditions, but then either fall to fungal diseases prematurely, or simply reach the term of their natural lives much sooner than plants grown ‘hard’, with minimal soil nutrition.

There’s whole books (or Ph.D theses) in this thinking, and it’s not my intention to do anything here but to introduce an idea that will either undermine a lot of your assumptions, or confirm your suspicions, or possibly make your brain hurt.

The brand new garden at Knepp Castle, planted into pure sand and crushed concrete (sourced from a demolition project on the site)

To summarise, when gardening for dry conditions, it may well be beneficial to minimise soil nutrition.  In some locations this is being achieved by the removal of top soil, and stripping back to subsoil.  In some other designs, the whole planted area is being spread with at least 200mm of sand or gravel, and plants planted straight into this skeletal substrate.  Both lead to sustainability questions for me.  I’m yet to form any opinion in opposition, and I’m totally intrigued by both of these approaches, but there’s questions to be answered.  At bare minimum, if you’re planning a dry garden, or at least a garden using drought-tolerant or dry-loving plants, think twice, thrice, or more before you add any nutrition to your soil whatsoever.


  1. yikes! I’ve just started my borders, adding sheep poo, compost, sand or whatever I can get my hands on as I go, Drainage in clay soils – part 1 of your blog, tick, But part 2, what’s the saying? the more you know, the more you know you don’t know. Or something like that. Thank you it’s so thought provoking.

    1. Hi Julia, And of course if depends on what you’re trying to grow. All that manure can work against you if you’re thinking of a drier, Mediterranean palette, but if you have some water for over summer, then a more traditional palette of border perennials or showy shrubs will likely love it

  2. Hi Michael,
    This is such a valuable topic. As a designer and installer of gardens I find the conditions in parts of Melbourne very difficult. We drown in winter and dry out severely in summer. Finding the balance for both is not easy. I do find however without added nutrition when planting, the growth is stunted and can take a lot longer to establish a garden even with dry garden plant selection.
    I will read with interest and will myself investigate further. Thank you for starting this conversation.

    1. Yes, it’s incredibly tricky. What Peter Korn in Sweden finds, when growing in pure sand and with no added nutrition, is that plants barely move for the first year. That’s hard to justify to clients who are always impatient for impact (as am I, come to think of it). When I made my first garden 25 years ago, I loaded the soil with compost, and the growth was crazy-fast! Thrillingly fast! I’m honestly not sure how relevant this thinking is to professional garden design – yet! it’ll get there!

  3. Good points ,well made .It never ceases to amaze when people tell me they have poor soil -it really is about matching the plant with the soil/cliamtic conditions not the other way round in my opinion.

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