Need Help?

Allan designs and plants flowering gardens in Montreal, Zone 5 [USDA Zone 4] .

See website, design work and favorite flowering plants at

Consultation and coaching for do-it-yourselfers is provided. Occasional emailed questions are welcome and answered free of charge. Oui, je parle francais.

See my work on Pinterest at Garden Guru Montreal

Entries in clay soil (3)


Gardening in Hard Clay Soil or the Importance of Being Stubborn

The last two homes I lived in were built on hard packed clay. Gardening was challenging. Unlike my colleagues who have made peace with nature and plant only what will grow in dry or wet clay, I was never prepared to compromise or surrender. I am flower deprived because my growing season is short. That’s why I was determined to plant everything on my wish list. Clay was not allowed to be an obstacle. I found a way to overcome the situation and now I grow whatever l like that will thrive in my zone.

I amended the clay soil according to prevailing conventional wisdom of the times [it was many years ago]. Not only did I create a fertile, clay-based growing medium, but also I inadvertently created elevated flower beds. The additional quantities of garden sand, organic matter, and quality earth, used to amend the clay, increased the height of the beds by two feet. Now, they were sufficiently elevated and amended for perennials and roses to thrive. If ever their roots would reach a layer of unamended compacted clay below, they would have no difficulty penetrating that level. The soil would have softened and lightened over time, with the help of the nutrient-rich humidity and natural occurring elements in the organic matter above.

Today, soil scientists advise us not to use sand because it impedes proper drainage. Nevertheless, I continue to use it to help loosen hard soil. I break up the surface of the dry, hard packed clay with a shovel, making certain that the blade deeply penetrates the clay, spread a thin layer of garden sand over it, and power spray with a garden hose nozzle set to jet. The pressurized combination of water and sand penetrate the man-made crevices, making it easier to till and blend the soil with the other additives.

For those readers whose homes are built on large tracts of clay, I would not recommend amending expansive areas of land. The high cost of purchasing and spreading good quality organic matter, [sea compost is the best] that might help alleviate the problem, puts a damper on projects of such magnitude. I would suggest paying attention only to growing beds.

Beside sea compost, here are additional organic additives that one can include in the mixture of amendments to help convert clay soil to loam:- Chipped straw, composted manure, autumn leaves that have been shredded by the blades of a lawn mower, kitchen scraps [must be buried], old decomposing mulch, confetti from an office paper shredder, ripped up newspaper that has been soaked in water, shredded, waterlogged cardboard from boxes and cartons, coffee grinds, shredded pure cotton wadding, crushed egg shells, vegetable and fruit peel, coir, lint from a clothes dryer, bread crumbs from the catch tray of a toaster, composted garden waste, gypsum, peat, peat moss, rich black earth, and garden lime.

Some with generous budgets have successfully used perlite or vermiculite as humidity trappers for dry clay. Gardeners situated on wet clay, who experience spring flooding, might consider gardening on berms, higher wall-reinforced beds [decorative materials are available], or in large containers. These elevation solutions are necessary because pooling water may overwhelm beds that are only two feet off the ground and damage plant roots. Environmentally correct gardeners will avoid using peat or peat moss because these are not renewable resources. In the UK, a tax on peat is under consideration. However, in some areas, peat moss may be the only affordable organic additive available. Coir is one of the most renewable resources because it is nothing more than ground up coconut shells. It also provides work for poor laborers in third world countries.

For those who have been dreaming about planting beautiful perennials and roses but were stymied by natural occurring clay, I hope this post will be an inspiration to think outside of the box. The trick is not to plant at grade level but at least two feet off the ground, or higher.


How Do We Grow Perennials in Mucky or Hard Packed Clay?

We don’t!  We build a raised flower bed of good, well-drained soil on top of the clay. In a previous blog titled “The Worms Ate My lasagna”, dated January 31, 2009, I suggested lasagna composting to build an arable garden over clay soil. That solution requires the gardener to wait a full season to allow the compostable materials to transform the soil. If waiting that long is not an option, here is a more immediate solution.

Over the clay surface, sprinkle garden lime, gypsum and blood meal, and moisten well. Add layers of any, or all, of the following items: coffee grinds, crushed egg shells, sawdust, cotton dust from the clothes dryer lint trap, perlite, vermiculite, cotton seed meal, newspaper, paper bags, rock phosphate, shredded paper, decaying leaves and spent mulches. Moisten again. Cover with a three inch layer of store-bought pure marine compost or homemade compost and moisten again. Add a two foot layer of the best quality garden earth available in your area. On top of that add a one inch layer each of peat moss and top soil. The flower bed is now ready to be planted.

As planting holes are dug and refilled, the compost, earth, peat moss and top soil will blend together. If  planting roses, blend Epsom salts into the back fill of the hole dug for the roses. Sprinkle more on the ground under the planted rose bushes. If planting rhododendrons, sprinkle additional peat moss around the trunks of the shrubs, making certain that the peat moss does not touch the trunks. Don’t forget to water the newly planted perennials.

In the first two years, the root systems of the new plants will not be strong enough to prevent erosion of this raised bed. Here are several options to prevent erosion:-

1] Surround the exterior perimeter of the bed with large rocks to contain the soil.

2] Place treated wood beams around the raised bed to wall in the earth.

3] Plant a border of hostas or low growing ornamental grasses to frame the bed. Planting daylilies at some of the corners and edges of the bed is another anti-erosion technique.

During autumn and winter, a combination of heavy rain and the weight of snow will erode or compress the earth of the new flower bed exposing the newly rooted plants to cold. Preventive protection is a good idea so in late summer or early fall, add a one inch layer of marine compost, followed by two inch layers each of garden earth and peat moss. These protective layers will contribute to insulating the new plants and need not be repeated in following seasons unless there are additional signs of erosion. In autumn, these protective layers should be in place prior to planting spring flowering bulbs, such as tulips and daffodils.


When I Made Compost, the Worms Ate My Lasagna!

click on the image to learn more about worms in the garden.Preparing a flower or vegetable bed in hard packed clay used to be back-breaking work. Today, professional gardeners frown upon digging into clay in order to improve it. Some recommend a no-work method that allows the gardener to conserve strength. That process is called Comforter Composting or Batch Composting. It has also been labeled “The Lasagna Method” because of the layering technique used to create arable land. Here's how it’s done:-

1] Start in early spring.

2] Using an aerosol paint spray or garden hose, delineate the desired shape of the growing bed directly on top of the clay, grass, or weed patch.

3] Sprinkle that designated area with garden lime [calcium carbonate] and/or Dolomite [calcium magnesium carbonate] and/or Gypsum [calcium sulphate] and/or blood meal. Use whatever is easily available; try to add at least two. However, be concerned about commercial blood meal. It is no longer as nutritious as it was twenty years ago.

4] Cover with ½ inch layer peat moss or reconstituted compacted coir

5] Cover peat moss/coir with any of the following: two sheets of newspaper, supermarket brown paper bags, paper towels or contents of a paper shredder.

6] Moisten paper layer.

7] Over the wet paper, spread a 3 inch layer of green garden waste including grass clipping followed by decomposed leaves [if available].

8] Sprinkle with nitrogen-based Compost Accelerator and moisten. The accelerator is optional; the moistening is necessary.

9] Add a 1 inch layer of any good compost [homemade is better but store bought will do; Marine Compost or Forest Compost is preferred] and moisten.

10] Cover with 1 inch of any type of garden soil but not clay.

Repeat the layering procedure beginning at step 4, until the new garden bed reaches a height of 15 or 25 inches, depending on which of the following two options is preferred.

Option A: When the 15 inch “lasagna” decomposes, the clay beneath it will be sufficiently malleable to blend clay and compost together with a 4-pronged digging fork. By autumn the mixture will make an excellent growing medium, ready for planting.

Option B: To avoid the hard work of blending clay and compost, make sure from the outset that the “lasagna” will be 25 inches high. By starting  with a higher “lasagna” in the spring, one may ignore the clay underneath and plant directly into the new raised flower bed in autumn.

Both the 15 and 25 inch “lasagna” will benefit from continuous build-up of layers throughout the following growing season as more organic matter becomes available. In late autumn both will also benefit from additional layers that will over-winter.

Three more tips:-

- Keep the “lasagna” moist all season.

- Used coffee grinds, crushed egg shells, stale snacks and munchies and any other non-aromatic organic matter make a tasty addition to the “lasagna” recipe as long as they are buried under soil.

- Stubborn and perennial weeds that reappear and cannot be removed should be sprayed with any brand of controversial glysophate-based systemic weed killer, if such a product is still available.

Now what does this have to do with worms?

First, true blood meal sprinkled directly onto the clay surface makes that soil even more attractive to worms. When they burrow into clay, worms aerate the soil, making it easier for plant roots to take hold there. Second, all living organisms in the earth, including bugs and worms, eat decomposing organic matter and eliminate their body waste into their surroundings. Worm waste is the best fertilizer!