Tuesday 8 May 2018

Gardening on rubble

Repeat week Golden Oldies
This post originally was published  under the title below. It is a rather long post reflecting the many situations were gardeners can benefit from an apparent problem.

Hardcore Gardening  

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 shifted 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 much 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 Lilian’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

Plants thrive here that survive nowhere else in my garden
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 now 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 sometimes 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 in one place 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  roots will explore for many metres. As long as roots of normal plants can reach moist 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 Holy island cottage where we recently stayed

Surprise, surprise, wallflowers like walls
Valerian was the star at Chelsea two years ago. Here together with toadflax this costs a little less!
The village plot still has the foundations of two old stone cottages

Aubretia likes walls too
(April 2018) Domestic altercation

I love this self seeding perennial corydalis that appears every year in the brickwork at the corners of our courtyard.
Neatophile Brenda, confessed fair weather gardener disapproves of my 'natural methods'. I have been worried that in this lovely weather she would get outside to remove it before yesterday's Open Day. Fortunately she didn't. She can do what she likes now and as a well established perennial it will be back in flower next February

 link to my post on gravel garden

link to my houseleek post

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