Tuesday, 29 April 2014

Hardcore Gardening


Gardening on rubble


When buildings and roads are constructed they are built on firm foundations of rock, concrete and stone.It is frequently deep and often compacted. This ‘hardcore’ is essentially stone. Wherever I see derelict remains of buildings and roads I see weeds. Nature has provided numerous plants with  the characteristics to survive and thrive in such conditions. Substitute interesting and beautiful plants for the weeds and you have a new garden!

After each of the Ice ages much of the Earth surface was rubble, rocks and moraines. Most of our plants in their turn in ecological successions have colonised such stoney foundations and over the millennia fertile soils have formed. Many plants like natural rocky outcrops and have root systems well adapted to grow in deep, sharply drained substrate. Numerous plants have remained  unchanged from those that thrived on early prehistoric stoney landscapes. Some of our garden plants do better in hardcore than anywhere else!

Some plants have been inadvertently preserved over thousands of years on a succession of man-made stoney foundations. Richard Mabey in his fine book  ‘Weeds’ charts vegetation’s preservation on ruins and ancient classical monuments. When they weeded and destroyed the rich 2000 year old resource of 420 documented wild plants on the Colosseum more than 150 years ago he portrays this vandalism as a crime against antiquity. In Mabey’s words, professional archeologists scoured more history from that great monument than any story that could be told by the mute stones.

Hardcore is not always deep and if ‘normal’ plant roots are able to grow through it there is often fertile soil below. If given a little help with a fork or a crowbar and perhaps by infiltrating some compost or soil not only will our regular plants grow well, some might do even better than normal. Plants such as clematis and hollyhock love a free root-run deep and wide within a water conserving mulch of broken stone.

When as a retired lecturer I was re-employed for a day to help with a student landscape project I casually stooped down and planted a plant in a gravelled hardcore path. My former student who was directing the project gasped in astonishment when his former soil-management lecturer stooped so low to abandon his soil! I expect next day they lifted the plant. There have been many cases since then I have planted amongst rubble and stone.

Case 1
A former client had the stoney foundations of a former outhouse on the north side of her house. It was a weedy eyesore. My attitude to redesigning a garden is to convert ugly features into attractive highlights and this was a garden with a great deal of potential. The hardcore was only about 50cm deep and planting holes could be broken with not inconsiderable effort. It was infinitely more to my taste and energy levels to plant into this than to replace the stone!  My penchant for planting small plants made my task relatively easy. After planting with all manner of plants, many rare and including herbaceous perennials, dwarf shrubs, alpines, bulbs and many self seeding plants it was mulched with an attractive builder’s gravel. It was perfectly practical to pop in extra plants later. Almost all the plants thrived. Some such as wonderful celmesias, I have never seen better.

Case 2 Lillian’s border


When Brenda’s mother died ten years ago I planted a small border in remembrance, at her sister Angela’s home. A farm hardcore drives goes close right up to the side of the house. I bought three dozen small sturdy alpine and creeping plants from out favourite nursery at Reighton. It’s a lovely ride for us to the seaside plant centre over the Yorkshire Wolds. Better for me to plant potted plants than divisions from home as I would not be there to regularly water them during their establishment. I broke up the hardcore deep enough to enable root penetration to the soil  below and planted in a strip perhaps eighteen inches wide. Each time we visit every two months or so, I spend ten minutes maintaining the plants. I sometimes take my sprayer to eliminate the weeds although more usually than not, I just pull them out. Some of the plants now have spread further over the drive. I suspect the farmer looked askance at the idiot planting into the road. I notice now that our antirrhinums have seeded over to his side of the road and make a beautiful display

Case 3 My border at home


The back of my house faces south and provides me an opportunity to grow tender and rare sun loving plants. A small length of the border has extra heat  which escapes from our coal fire on the other side of the wall. The  original ugly concrete four foot wide footpath had to go! I chipped out the concrete leaving the thick hardcore in place . The overhang of the roof provides excellent shelter for a dozen or more hardy cacti. Covered with gravel, the rubble joins seamlessly into my gravel mulched rock garden. The window cleaner still has plenty of spaces to walk on the gravel and we can enjoy special plants hugging the base of the wall. Plants grow there that would not survive anywhere else in my garden. The plants include Cyclamen cyprium, nerine, dendrathema, vallota, dwarf alpine primulas, Dicentra cucullaria, Corydalis solida, yellow brodea, Sternbergia lutea and numerous dwarf bulbs, many ‘difficult’ and some rare. Even Begonia sutherlandii thrived for four years until the 2010 double Winter. In Summer when I water my tubs I also give my partly sheltered border a drench.



Do not confuse my gravel garden with a hardcore garden, although sometimes they may be much the same!


The Scarborough lily, vallota is not supposed to be hardy. Mine conveniently flowers every year on cue for my Open day, the first Sunday in September. It even survived the 2010 winter!

Brodea ‘Yellow Star’ sends up its flowers after the leaves


Case 4 Bolton Percy Parish Room yard.
Bolton Percy Primary School closed in 1949 and became the Parish room. The old tarmac playground remains undisturbed (other than my plants) to this day and is covered by a deep mulch of sixty years of leaf litter. Now rather crumbled the tarmac only needs a sharp chop with the spade to insert cuttings or plants which can then spread and self seed in the cracks. Many are wild flowers. It is a wonderful shaded habitat for woodland plants such as hellebores and ferns. I planted a lovely Amelanchier canadensis in ‘Tree Planting Year 1973’ and added in 2000 the village Millennium tree, Sorbus ‘Joseph Rock

Case 5 My roofless roof garden!


At the bottom of my garden a very large concrete slab covers an old well. Too difficult to remove, I covered it with an old carpet (!), two inches of soil and the shards of excavated stones that I bring home from my  monthly maintenance visit to Worsbrough cemetery garden. Such an environment is only suitable for a limited range of mainly succulent creeping plants such as sempervivum and sedum. It does keep me in tune with trendy fashions and as the concrete block is a barrier to the capillary-rise from the high Winter water table below, my succulents are not drowned. Adjacent, I have created a raised rubble garden higher than the occasional Winter flooding. You will not by now be surprised by now to hear that I buried beneath it an unwanted 1970’s stone fireplace!

Case 6 Mainly climbers at the foot of walls and the house.

My house is more than two hundred years old and concrete surfaces, tarmac drives and posh paving has been repeatedly laid by former owners. We like to have climbers and wall shrubs on most of our walls. As long as one creates planting holes deep enough for roots to thrust through the rubble to reach the soil and/or loose hardcore below, once established, such plants will thrive.  Newly planted plants  need  a little cosseting to get them going. The very deep concrete at home needed a builder with his noisy concrete busting gear. He had to be very well supervised to make sure he broke all the way through the concrete. Builders tend to think that a shallow depression is all plants need!
My very best climbing yellow dicentras particularly thrive tucked at the base of the house wall surrounded by loose paving.

My mixed planting of a white and pink chaenomeles is not quite as intended but they both grow very well. 

Cultural notes
If your rubble is full of perennial weed such as couch and bindweed you will need to use a translocated weedkiller such as glyphosate before you plant. It is nye on impossible to eliminate such weeds in any other way.

Roots grow deeper and wider than most none-gardeners think. Some  will explore for many metres. As long as roots of normal plants can reach wet soil they will thrive. If adjacent horizontal mineral surfaces are porous they will provide a wonderful water conserving mulch. If impermeable concrete stretches a very long way you may have future cultural problems when the spreading roots permanently dehydrate the ground.

Most of my rubble gardens do not receive extra nutrition, but some do. There can be greater benefit to gain by scattering general NPK fertiliser over the stone than when plants are just in soil.

Covering hardcore with gravel not only looks nice but increases the opportunity to establish plants from seed.

Nature has had very little help here.

The only help these self seeded plants have had from my sister Marilyn and husband Dave is pulling out a few weeds.
I love sempervivums. They looked fantastic in the wall of the holiday cottage where we recently stayed

Not a surprise, wallflowers like walls!
Valerian was the star at Chelsea two years ago. Here together with toadflax it costs a little less!
The village plot still has the foundations of two old stone cottages

Aubretia likes walls too

10 comments:

  1. It's quite mazing to see established buddleia growing in inhospitable places too. On the plot our limnanthes are heading across the tarmac

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    1. You and others Sue might be interested in my recent experience with my Limnanthes at Worsbrough cemetery garden. You will remember I have masses of it there that self seeds every year and which I have previously posted about. On my last visit I met a nice old gentleman who had harvested three quite large bags of it and told me he had been doing so all winter!. Fortunately although he thought it was just growing wild (everyone at Worsbrough thinks my plants are weeds) he had cropped a portion of the leaves and NOT pulled them out!
      He was feeding the leaves to his hens and said he had never had such yellow eggs. As you know its common name is poached egg plant!
      The doctrine of signatures is not dead!
      I have also naturalised it in Cathi’s garden next door and her hens range freely. They have not yet discovered this delectable food!

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    2. Good job it wasn't poisonous!

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  2. Roger, first of all, thank you for giving us the link to the Blog 'Fleeting Architecture'.
    Half of one of my allotments is literally just a big pile of rocks from when they put a new rail track down beside them.. the excess were just dumped and I was told the price would be less because of this. But I wanted a group of trees there, so I spent hours and picked out four holes and loosen a bit more, planted 4 fruit trees there and hoped for the best!
    Bless their hearts, not only did they grow but last year I had 'good' fruit from 3 of them and a couple of Pluots from the four who is taking her time about getting big and strong like her neighbours. Root are extraordinary things. Thank you so much for your blog and your advice that you give us. Sara.

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    1. I see from your blogger profile Sara that you pretend to be a parrot and comment about hardback books!
      All our books are shredded by our parrot Poppy (actually a love bird)
      I had to look up pluots being somewhat out of date! The hybrid prunus - plums apricots etc look delicious!. I am sure you fruit is going to be fantastic and you will have no problems with drainage!

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  3. Another fascinating post Roger, your reference to the Ice Age pretty well sums it up. The perceived wisdom given to people wishing to grow many alpines is to basically to put down a 'hardcore' base and then top it up with a layer of gritty soil topped with a layer of grit to create an artificial environment. What you have done is to achieve the same thing by adapting the existing conditions without all the hard work and extra expense. I admire all the informal planting, I dislike formal gardens intensely, plants weren't meant to grow in straight lines in square borders.

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    1. I imagine your own garden - and I have seen pictures on your blog - is very much to my taste Rick

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    2. How very interesting and not for the first time spot on cue; our son has just been left with a huge pile of rubble and stone blocks as a result of excavations for ground source heating. Maybe the heap, currently the size of 2 or 3 tractors, will become a few walls and then a rubble garden. Inspirational as always!

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  4. I never thought our patch would feature on your blog!

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    1. I have a nice picture of your Virginia creeper on your house that I might use yet. And I am sure Dave's allotment has potential.

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