Our plan for the next couple of years to the set up a row of vegetable beds running east-west in the back garden and surround this with a bee-friendly perennial herb garden. However, most of our garden is currently grassed, and the compacted clay is not ideal for intensive growing. Therefore we need to look at building soil and creating an environment that will encourage healthy soil life necessary for plants to grow.
A single tablespoon of earth hosts around 50 billion microbes. By comparison, the human population numbers just over 7 billion currently. These organisms include Bacteria, Actinomycetes, Fungi, Yeast, Protozoa, Algae and Nematodes. Furthermore there are arthropods and insects in there as well, including earthworms. That’s a lot of life!
Plants grow by making carbohydrates (sugars) from carbon dioxide (CO2) and water (H20). They share these sugars via their roots with the microbes in the soil. The microbes, in turn, assist the plant by making nutrients more available to them with the enzymes they produce. Healthy soil also has a rich variety of mycorhizal fungi that attach to plant roots to feed off the carbohydrates plants produce. The vast web of mycorhiza strands in the soil extends the reach of the plant roots, providing water and nutrients to the plants. Fungi also break down dead material like woody cuttings and leaves to form soil aggregates
Healthy soil is high in carbon, is able to maintain moisture, retains nutrients and is full of life.
When we first moved in, the back lawn was edged by an obtrusive evergreen hedge that ran alongside the deck. This is right where we plan for the herb border to go. I gave it a heavy prune in March to see if it was worth keeping, but my topiary leaves much to be desired. It was ugly and still obtrusive so the hedge had to go before we could start building the garden.
Getting rid of the hedge wasn’t so easy. I only had a hand saw and the trunk was thick and gnarly. I decided then that I wouldn’t bother trying to remove the roots. They could sit in situ and my hope is that as I add more nitrogenous material, they will start to break down and create soil structure.
The Digging Conundrum
I stewed a bit working out how to start this bed off. The grass was heavily compacted so I would need to add a lot of organic matter on top, if I was to follow the no-dig method I used with the fruit trees. I wanted to build soil quickly enough to be able to plant this year, so I found myself toying with ‘double-digging’, which is considered a dirty word in some permaculture circles.
The problem with traditional double-digging is that it destroys the soil life that we are trying to build. It also mixes the top soil with the sub-soil, making the humus layer less nutrient rich. This goes against how roots naturally function, which is to have shallow thin roots spreading outwards to collect nutrients in the rich humus layer and thicker deep roots that mine the sub-soil. The no-dig philosophy argues that the soil doesn’t need to be tilled for magnificent forests to grow, and that adding organic matter on top of the soil is the most natural way to build soil and nurture the ecosystem.
However, if done carefully, soil layers can be maintained to some degree, the sub-soil is aerated and left intact and the exposed ground is protected by a layer of organic litter. In removing the topsoil, I was careful to keep the grass sods whole so as to protect organisms in them. Inevitably the odd worm met the blade of my spade, but I didn’t attempt to break up the soil more than was necessary to lift it. The importance of this was evidenced in the discovery of wee mushrooms in amongst the grass.
Build and They Will Come
The grass was lifted in sections, the clumps from the first area moved aside and the subsoil aerated with a fork. I then turned the grass sods from the next area upside down on the first area, continuing to aerate the subsoil as I went. Finally, after the last section was lifted and aerated, the clumps of grass from the first section were upturned onto the final section.
On top of the turned sods I then added a layer of cardboard sheet mulch. This was a bit awkward as the card didn’t sit easily on top of the rugged contours of the upturned grass, and I think wet newspaper would have been a better barrier and would have fitted more snuggly. As well as suppressing grass and weeds, the sheet mulch acts to protect the exposed soil, keep it moist and assists maintaining the integrity of organisms.
On top of the card I threw down a layer of organic matter that I had to hand. In this case it was more Zoo Doo and some recently harvested seaweed, and then applied a think layer of pea straw.
Fertility in the Rough
The end of the bed where the tree stumps are received slightly different treatment and I’ve started a bit of an experiment in this area. I did my best to aerate the soil but this was difficult because of the tree roots. I then laid down the partly decayed leaves and branches from when I trimmed the tree last March. These had started to decompose and were showing evidence of fungal growth. I have since added whatever nitrogenous organic matter I can find over the tree stumps. Grass clippings, coffee grounds, compost, urine etc. I read somewhere that decomposing hardwood is initially very nitrogen hungry, depleting the local soil, and starving plants of this essential mineral. So I’m going to apply thick layers of nitrogen-rich materials over the woody material, which is on top of the tree stump roots, throw in some flowering herbs…and see what happens.
I have planted a few herbs in this area so far: Yarrow (Achillea millefoilum), Evening Primrose (Oenothera biennis), Hyssop (Hyssopus officianlis), Clary Sage (Salvia sclarea), all grown from seed, and the plants seem to be fairing pretty well so far.
A few months down and the soil life is really starting to hum. I’ve been planting my herb seedlings in this bed and so far they are all doing really well. All except perhaps the catnip (Nepeta cataria) which has been bothered by numerous nefarious felines.
A good example of how well things are going can be seen in the resurrection of my wee lime tree, nicknamed Jesús. My poor tree arrived in the middle of winter along with my apple tree purchase. However, he was left neglected outside for the winter months while I decided where to put him. As a result, he didn’t fair so well in the cold and lost all of his leaves. I assumed we had lost him.
In a bid of desperation, I dug a hole in my newly created bed, with little hope that the humus layer would be ready enough to offer any support. But lo and behold! Jesús has sprouted once again, new growth in his leaves and is starting to look mighty strong.
The rest of the bed is doing well too. Parsley has taken off, along with sage, marjoram and thyme.
I’ve also thrown in a few random things the kids were growing in pots to get some ground coverage . There’s a brassica that was sprouted at Guides, and some dwarf bean seedlings. I jammed some geranium and rosemary cuttings directly into the ground to see if they would root. So far so good.
And things seem to be surviving down the “rough end” of the garden too. Clary and Yarrow have found their feet, and I’ve even squeezed in some tomato seedlings that needed a place to live.
This bed still has a long way to go and time will tell what my wee experiment will yield. I will keep topping up this bed and others with compostable material and maintain a good layer of mulch. But I am already confident that life is returning to the soil (as it has to Jesús.