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

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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.

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Reader Comments (4)

As one who gardens on hard clay, I have used many of the amendments you mentioned. Your advice is excellent. I also add a layer of mulch around all of my established plantings once or twice a year, and over the years the continual breakdown of the mulch has improved the top layer of soil. I use pine straw, as well as leaf mulch. My soil is mostly acid, so this works well.

February 23, 2011 | Unregistered Commenterdebsgarden

Thanks for "amending" my list of amendments. Covering the soil with a layer of mulch on a regular basis is an excellent idea.

February 24, 2011 | Registered CommenterAllan

I have some clay but not to the degree you do. I have added organic matter every year as well as gravel and it has over the years really improved the soil

February 24, 2011 | Unregistered CommenterHelen

Thanks for the info, Allan! I'm working with excellent soil now, but I have gardened in clay soil in the past. It's challenging. Thanks for the tips!

February 24, 2011 | Unregistered CommenterPlantPostings

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