I had the occasion last week to check out a large-scale landscaping project. What I saw horrified me! Two new large perennial beds, very professionally hard-scaped with beautiful stone, had been filled with soil last fall. Instead of a beautiful loamy planting bed I was astonished to observe a veritable witches’ brew of six or seven of the most invasive weeds that a gardener can imagine. These are the weeds that cause gardeners to wake up in the middle of the night screaming in a cold sweat. Imagine if you will a cocktail of burdock, sow thistle, Canada thistle, Japanese Knotweed, quack grass, Japanese lantern and colt’s foot – the only plant missing was goutweed!!
I cannot fathom where a landscaper would have been able to find such soil. I cannot even concoct a scenario where all of these thugs would have been found growing together. I believe that the only feasible approach to this apocalyptic landscaping nightmare is to carefully remove all of the soil from the beds and start over with screened topsoil (probably a triple mix) from a reliable reputable garden centre.
As in many things in life, the cheapest deal is not always the best deal and in some cases can be disastrous. This holds true for gardeners and perhaps for countries as well!
Start with the soil
While your garden may already be completely planted, I think that a short primer on soil may be in order – probably the best advice that I ever received with respect to growing plants is “feed the soil and the soil will feed the plants”. While it may be too late for wholesale amendment to your soil, plants will appreciate a side-dressing with well-broken down composted organic matter.
Nothing is more discouraging than soil that sticks like glue to your boots when it’s wet and then bakes to the consistency of cement in the middle of a long, hot summer – weeds are impossible to pull out and vegetables fail to thrive. Almost as difficult is soil that feels like you are at the beach – any amount of water just seems to disappear. I have tried gardening in both and I think they are equally discouraging. It usually comes as a surprise to the neophyte gardener that the solution is the same – the best way to improve any soil is by the addition of compost.
The extremes of soil size are sand and clay – sand has the largest particles and clay the smallest. Bacteria in decaying organic matter cement together individual soil mineral particles into clumps and greatly improve soil structure. Soil structure is important to retain moisture and for the movement of oxygen and carbon dioxide. A good soil composition is made up of 25 % air, 25 % water, 45 % mineral source and a minimum of 5 % humus (compost or organic matter). The proportion of organic matter could be considerably higher.
The holy grail of the gardener is soil with excellent tilth. The tilth of the soil is basically its workability. A well-balanced soil holds water without becoming soggy. It allows air to penetrate to plant roots and soil organisms. It is loose and easy to work.
The pH scale, from 1 to 14 measures acidity or alkalinity of the soil – A pH of 7 is neutral. Solubility of most nutrients is highest at a slightly acid soil – the optimal range is 6.3 to 6.8 – some plants, such as blueberries have very particular needs for an acidic soil.
Simple home test kits are available. Testing at a commercial lab is also a possibility if a problem is suspected.
I have found that most vegetables are pretty happy with local soils. It is very difficult to change the pH in soil – it requires huge volumes of amendments. If your soil is alkaline and you have your heart set on growing blueberries that require acidic soil, make a raised box, fill it with sandy soil and then add acidic amendments such as pine needles or sulphur. It is much easier to change the pH of sandy soil than that of clay soils. Know what you can change and what you have to learn to live with – it is much easier to just simply say NO to blueberries!
There is a theory that the limiting factor for plant growth is the nutrient that is the scarcest nutrient in your soil. One could do endless expensive soil tests to analyze the nutrients in your garden, determine which ones need to be added and then go out and buy those nutrients, figure out the application rate and then add it to your garden OR one could just add compost to the garden. It generally includes all the micro-nutrients as well as the 3 macro-nutrients. This fixes everything because compost is derived from growing plants that, by definition, had everything that they needed for the growth that they achieved.
Commercial fertilizer labels, such as 20-10-10 show the percentage of soluble Nitrogen, Phosphorus and Potassium. Most organic materials are of low solubility so will have 1-1-1 labels. So is the chemical fertilizer 10 to 20 times better? Of course not! All that is being measured is how much of the nutrient is immediately available. Organic materials will provide ample nutrition over time but little will immediately dissolve in water. And organic materials improve the structure and tilth of your soil. Chemical fertilizers provide quick symptomatic results but do nothing to improve the health of the soil.
In order to determine if soil is workable, take a handful and squeeze – if it stays together in a ball it is still too wet, if it crumbles it is ready. If it sticks to your shovel or boots it is not ready. Raised beds and well drained soil assist an early start by warming up much faster.
Avoid compacting soil and destroying that tilth you have worked so hard to create – do not walk on the beds and do not overwork the soil!!