What makes a successful garden? Is it the physical landscaping of your property, the artful colour combinations and seasonal bloom of plants in your gardens or a dizzying number of plants in your plant collection? Each of these is important, but not nearly as important as what they are growing in - the soil.

This page focuses on how to make your gardens successful from the soil up. You'll find tips and explanations on soil building, maintaining soil health through composting, and creating special soils for specialty gardens such as rock gardens and bogs.

Carole and I have been gardening for over 30 years. We've learned (often the hard way) much about gardening in that time. Fortunately, successes have outnumbered failures. For the past 24 years we've run a specialty nursery, just west of Carp, raising and selling perennials (and now flowering shrubs, conifers and pond plants) . We've developed 23 demonstration gardens on our heavy clay soils as teaching aids for our customers. 'Successful Gardening' reflects on our experiences. The principal lesson we've learned is to work within the natural conditions of your property. Anything else can be very expensive!

Successful gardens begin long before the first plant goes in the ground. In helping our nursery customers diagnose garden difficulties, the problem is often the wrong plant choice for their property's existing soil. The fix is to change the plant selection or change the soil.

Plants, like humans, are the product of 'what they eat'. Roots are the most important part of a healthy garden plant. Healthy roots support showy leaves and flowers. Successful nutrient uptake by plant roots requires a soil composition with the proper balance of air spaces, moisture, nutrients and healthy populations of soil micro-organisms. Roots require air to take up nutrients. Some plants tolerate or even thrive in low air-containing, constantly wet soils. Others need extremely well-drained, airy soils. It should be no surprise that different plant varieties have a range of requirements. The fun of gardening is learning what individual plants need.

Your first gardening expense should always be to get the proper soil for your property. For the average gardener this means, if you've now got clay soil, bring in sandy garden soil to help improve drainage. If you're starting with a sandy soil, you'll want to import a clay-based soil to help with moisture retention. If you're on bedrock, you'll need a garden soil with a mix of clay and sand. Unfortunately, we've not a found a local soil supplier that can supply all the soil types needed by the range of aspiring home gardeners. Soil suppliers in our western Ottawa regions tend to supply either excessively sandy soils for garden needs (but great for lawn creation) or heavy clay soils needing further amendments. Soil suppliers from areas east of Ottawa, where native soils contain more organic matter, tend to supply soils more suited to ornamental gardens. You are best to examine first-hand any soil before ordering it.

In the next article we'll look at what makes a good gardening soil.

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Gardening success hinges on understanding the limitations of your existing soils. Is there a “right” soil? That’s a hard question. Most soils will grow something.

Knowing some history of your property can be helpful. If it was very recently a woodlot, then your soil will likely have a fair bit of organic matter in it, be quite light and airy, and with a shade tree or two, be able to grow a wide range of plants. If it was an open field, you’ll have different conditions. This shouldn’t be a problem, but your plant selection will be those which are primarily sun lovers. If it has been a long-time residence with no established gardens, then your soils are likely in need of structural (to provide better drainage) and nutrient rejuvenation to produce a successful garden no matter what their origin. In newer subdivisions, expect disappointments in your property’s soil. Bedrock or rock fill is likely only inches away from the surface.

Before investing good money on pretty plants, you should do some exploratory digging around your property to learn about your soils. Don’t assume that the soil on your property is uniform. Next to the house foundation and along fence lines are prime garden areas. On bigger properties, dig in the middle of your property too as you may want central island beds as part of your landscape design. When digging, keep the holes small and try to go two feet (60 cm.) deep – perennial plant roots generally need deep soil. If digging in lawn areas, carefully lift the sod for reuse. When you replace the sod, keep it uniformly moist for a couple of weeks to get the grass roots re-established.

Start a gardening notebook – it’s worth it. In it, record the location, depth, and texture /composition of soil at each hole.  Draw a simple map of your property to identify hole locations. While you’re at it, draw in shade trees, utility services (especially buried hydro and waterlines), pathways and driveways. These obstacles should ultimately guide where you place your gardens. You don’t want to dig up a successful garden to repair a utility problem!

Using an old-timer’s trick can give a quick clue to soil composition. Simply spit on a pinch of dry soil sample (to moisten it) held in your hand. Rub the soil between your thumb and forefinger. Clay soils will feel slippery, sandy soils will feel gritty. You’d like it to be mostly gritty and somewhat slippery – gritty from sand, slippery from clay.

To get better information about your soil composition, collect a cup of soil, with portions from various depths of your diggings, from each hole. Place each sample in a tall jar with a screw-on lid and add twice the amount of water. Added one drop of dishwashing detergent to help the soil particles separate from each other. Shake the jar vigorously for a couple of minutes and let it stand overnight or as long as it takes for definite layers to form. Measure the resulting layers: sand at the bottom, silt in the middle, and clay on top. Calculate the percentage of sand, clay and silt in your soil samples. Sand, the heaviest will be at the bottom, then silt, with finer clay particles on top. Divide the thickness of each layer by the total height of settled soil and multiply x 100. (E.g. 2.5” of sand divided by 7.2” total height of solids x100=33% sand)

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From the above, you can calculate the percentages of sand, silt and clay in soil samples from your property. How do you interpret these results?

Soils contain varying amounts of mineral components: sand (the largest particles), silt, and clay (the smallest particles). Good garden soil ideally contains enough sand (about 30% - 60 %) to make it drain freely and create necessary air spaces for root growth.  Soils with 40% sand, 40% silt and 20% clay (called loam) are ideal garden soils. Too much sand (over 60%) causes soil to drain too rapidly. Too much clay (over 60%) creates poor draining soils. Good garden soil should have enough silt and clay to hold water in dry periods.

If you’ve got loam at 40% sand, 40% silt and 20% clay, rejoice – start planting anytime. If not, then your first gardening task should be to create a more root-friendly soil.

Can I provide a recipe for the perfect soil? The only ingredient I’m sure of is labour. The rest is, unfortunately, by trial. The soil test results are your guide. Your aim is to create the 40% sand, 40% silt and 20% clay (loam) for the average perennial garden. Remember, you want it to be 18 inches to 2 feet deep too. In your soil improvement program, you should repeat the above soil test to see if you are nearing your goal.

In clay soils, hand digging is the best way to create your improved soil. Work when the soils are dry so soil clumps can be broken apart. Rototiller blades have an unfortunate side effect of pounding the clay at the bottom of their rotation. This creates, especially when the clay is at all moist, a sealed layer of clay under your improved soil. This sealing reduces drainage ability. That’s not what you want. In clay soils there doesn’t seem to be a substitute for manual labour if you are going to do the job ‘right’ .

Who said creating a successful garden was easy? Treat the work as a workout. Your health improves with that of your garden soil!

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Poor drainage in moist clay soils is typical. To overcome this limitation, we added humungous amounts of coarse sand to improve drainage in our 60% clay soil,

I emphasize coarse because coarse sand particles have points that project against adjacent sand particles and create cavities for air. Choose concrete sand, not masonary or beach sand, for this chore.  Even fine gravel can be beneficial.

Aim to build a raised soil bed to facilitate drainage. A good starting point is 4” to 6”. Better still is 9” to 12”. What will you choose to contain the soil: wood, natural or artificial stone or something else? You’ll need something for smaller beds to prevent erosion. In larger beds it is possible to grade the soil and restrict erosion with surface mulch applications.

Why raise garden beds? Adding sand or organic matter to clay makes it more porous and allows rain and spring run-off to get into your newly improved soil faster. Without a raised bed, you’ve actually created a ‘pool’ surrounded by poorly drained, unimproved soils. Trapped moisture is confined: it has nowhere to go! A raised bed, however, allows moisture to escape onto adjacent lower areas. As the moisture seeps out, air is sucked into the resulting soil cavities much like the human action of breathing.

Clay soils are often lacking nutrient-rich organic matter too. In our early days we grew green manure crops (mostly deep-rooted buckwheat) to add organic matter to the clay soil and to create deep channels in the clay when the roots decayed. These crops were mowed down and tilled into the soil. With buckwheat, its possible to get three crops a year. Over the years we also applied every kind of manure we could find (including donkey ‘poo’) to add organic matter into the soil. The organic matter also loosens up the soil as well as creating a rich population of soil organisms helpful in making nutrients available to later plantings.

We learned a lot in our early, formative gardening years and our gardens produced abundant fruits, vegetables and the beginnings of our perennial gardens

As our gardening interests broadened, we moved away from the veggies and the fruits and yearned to grow perennials requiring soil conditions different than on our property. We hungered for our field-like property to grow showy foliage plants best grown in shade. This is where we’ve had most of our gardening failures.

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See 'Some Final Thoughts' at the bottom of this page for problems with shade-loving plants grown in less than ideal conditions.

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A compost pile is a gardener's best friend. It is easy to build. There are only a few rules to making a compost pile that functions properly. The ideal result is a sterilized, nutrient-rich soil conditioner or mulch.

To do this, the entire compost pile has to reach a temperature of about 130 to 160 degrees F. (definitely hot to touch!) and maintain this temperature for 1 - 3 weeks. This can only be done if the pile is large enough (about 3' x 3' x 3') and has a good supply of moisture, air spaces and lots of nitrogen-rich material. A compost pile is literally a bacteria factory – it is the bacteria that produce the heat as they grow, multiply and feed on the plant material in the pile.

If sterilization of weed seeds and root pieces is not of concern, then the attainment of the high temperatures is not a must. Simple decomposition (rotting) can take place at lower temperature. But beware of this limitation. Also be aware that the typical backyard ‘Black Box Composter’ is too small to build up sterilization temperatures –especially if you are constantly adding material to it. Rotting, not composting, is the common process taking place in those contraptions!

How much area will a compost pile occupy? A garden 50’ x 10’ (15 m x 3 m.) will generate enough organic matter in the fall to occupy an area about 4’ x 6’ x 3’ high. It takes about 3-4 months for a compost pile to finish work if the pile is turned once a month. If it is turned every week, it will finish in about three weeks. You should not add new organic material to a pile that is in the active sterilization process. Depending on your plans for turning, you should leave enough space for at least a second pile to be created while the sterilizing pile is at work.

To build a compost pile that will reach the 160 degree F. temperature, it is best to build the pile in alternating layers like a layered cake. It is also best to build it in a shaded area to reduce the drying effects of sun and wind.

Here are the basic steps to constructing a compost pile.

• Build your compost pile in an area which is at least 3 feet square at the base. This area can be walled or fenced to help create vertical sides. Solid sides also help keep the exteriors of the pile moist.

• Create 8" thick layers of garden trimmings (plant stems help create air pockets), followed by 2" layers of fresh grass clippings (rich in nitrogen) followed by 1" layer of soil. The soil contains inoculants of bacteria and fungi to get the composting underway. If you have access to farm-yard manure, adding 1" layers will enrich your compost and help drive the temperature up to the desired 160 degree F. mark. If you add sawdust or straw to your pile (these don’t contain much nitrogen to feed the population of bacteria and fungi), add extra grass clippings and extra nitrogen-rich fertilizer. The smaller the size of material added to the pile, the faster bacterial breakdown of the matter occurs. Mechanical shredders are a great help if you plan to do a lot of composting.

• Sprinkle a dusting of bone meal over each soil layer: this adds phosphorus required by the bacteria to multiply quickly.

• Spray these layers with water to the point of being obviously moist but not waterlogged. Repeat this sequence until the pile is at least 3 feet high.

• Don't add diseased plant material, oily kitchen waste, meat or dog/cat feces. Also don't add wood ashes to any piles to be used as mulch in woodland gardens. This would create compost whose pH is too alkaline for acid-loving woodland plants.

• There is no need to add commercial compost starters if you add thin layers of soil for every 8” –12” height of your pile. Soil naturally contains the decomposer bacteria needed to inoculate any compost pile.

The following are some basic guidelines on choosing proportions of materials to build an ideal compost pile.

In practice, composting success is often limited by the amount of nitrogen-rich material needed to feed the decomposition bacteria. A carbon to nitrogen (C: N) ratio of 30:1 is needed for compost activity to proceed at its optimum rate. The nitrogen component should be much higher (e.g. 10:1) for piles which are turned to speed up compost production. Without enough nitrogen, the pile may not heat up at all. Saw dust has a C: N ratio of 511:1 and manures about 14:1.

The following table gives examples of materials with high carbon and nitrogen contents.

Compostable Materials 

Once your compost pile is built (or even in between creating successive layers) place a plastic sheet or other covering over the pile to help maintain the moisture level in the pile. Keep an eye on whether it needs added moisture. Simply plunge your hand into the pile and pull out a sample of the compost. If it is even slightly dry, spray the pile to re-moisten it. Without water, the pile can not heat up. Too much water on the other hand, drives out the air and creates an oxygen-starved pile.

Now is the time to keep an eye on the temperature of the compost pile. Make sure that the pile heats up and that it stays heated for at least a week. You should be able to see steam rising from the pile on a cool fall evening. If you plunge your hand to a depth of 12 inches and you can feel the heat, this will be a good indication that the pile is working properly.

At the end of a week at 160 degrees F., the compost pile will likely start to cool down. It is time to turn the pile inside out. Turning puts the outside materials on the inside of the rebuilt pile. This chore can be made easier if you have a second close-by place to re-establish the pile. You don't need to worry about layers at this point. But, do make sure that the pile is very moist. Sprinkle bone meal and perhaps some high-nitrogen pelletized fertilizer at regular intervals to stimulate the bacteria's activity.  The pile must reheat to 130 degrees F. (somewhat lower than the first temperature) for a second week-long period.

It takes 3-4 months for a compost pile to finish its work if the pile is turned once a month.  If a pile is turned every week, the time can be reduced to about three weeks.

After the second heating process has been achieved and maintained for a week, the compost is ready to apply to the garden. It will still have much of its stringy texture, but it should look blackened from the decomposition and heating process. Composting reduces the volume and weight of the original material by about 50%.

If the compost pile is to be left exposed to the elements over the winter, it is advisable to place a plastic covering over the pile to keep fall and spring rains from washing away all of the nutrients.

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Applying Composts and Manures.

When preparing a perennial bed for the first time, add about 3- 6 inches of compost or well-aged manure and work it into the soil to a depth of 10 inches.

To maintain soil fertility, a one-inch layer of compost added annually to most full -sun gardens is sufficient. For shade garden, a half inch of compost should be enough. This can be done at any time during the growing season, but is most effective if applied before the heat of summer begins. This may mean that you are applying year-old compost that has been stored over the winter. A one inch layer is enough to act as a mulch to keep new weed seed from germinating and will help keep moisture in the soil.

Manures of many types are beneficial additions to garden soils. Fresh manure is very rich in nitrogen and can burn tender plant feeder roots. If you use fresh manure, allow 8 weeks between application and planting for the nitrogen to be diluted by rains. Keep the manured soil uniformly moist during this 8-week period to ensure that the manure is decomposing in the soil. In a drought period, the manure will simply stop decomposing, only to resume when moisture becomes plentiful.

Manure application to established perennial beds is not recommended. Manures contain too much nitrogen for perennial plants to produce flowers. Manures cause perennials to produce heavy leaf production and no flowers. Backyard compost, richer in phosphorus than nitrogen, is the ideal soil enricher. Annual one-inch top-dressings to perennial beds provide the nutrient balance that favours perennial flower production.

Growing Cover Crops or Green Manures.

Good gardens are usually found on good soils. If you don't already have a good garden soil on your property, and in the city this is a real possibility, a gardener's main chore is to create one. Often soils are too compacted and lack organic material, or humus, required to supply nutrients and retain moisture for growing plants.

It is possible to import bought soil with the right composition for gardening ... but this can be an expensive proposition.

It is also possible to 'grow' a good quality soil right on the spot where the garden is to be located. The idea is to grow a cover crop whose sole purpose is to be tilled into your existing soil. This will build up the humus content of the soil, which in turn, helps make the soil lighter in texture, able to hold more moisture and which is more weed-free.

A cover crop is simply a crop of a legume (member of the bean family) or a grass chosen for its ability to grow quickly. When rototilled into the soil, it quickly decomposes and adds humus to the compacted soils. Buckwheat, peas and beans, alfalfa, clovers, wheat and annual rye grass are typical crops grown as cover, or green manure, crops. Buckwheat has a special appeal because it grows so quickly and densely (shading out other weed varieties) that it can be resown up to three times in a growing season.

If you are planning a perennial flowerbed, keep in mind that many perennial flowers are easily planted in the early fall.  Grow a green manure crop or two until the end of August and then plant your perennials. No time is actually lost.  In fact, on the plus side, soils on which cover crops have been grown contain more humus, have been relatively weed-free for a growing season, and have been enriched by natural fertilizers released by the decomposition of the cover crop plant material.

In vegetable gardens, wherever there is a bare spot during any season, why not plant an edible 'green manure' such as beans or peas. In the fall, after the last cultivation of your soil, plant a crop of annual ryegrass, winter rye or kale. In the spring this crop will be rototilled into the soil to add extra nutrients to the soil.

Because growing green manures is such a good fertilizer investment (many can be cut or mown to add to the compost pile), why not design your vegetable garden to be 1/3 larger than you plan to use? Sound silly? Not really, because now you can plan for crop rotation. Each year you can plant a cover crop on 1/3 the area to improve the soil (but not mowing lawn!). In the second and third years plant gardens on this area while growing a cover crop on another 1/3 of the garden area.

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Even today you have to be a library sleuth or avid magazine subscriber to stumble across really good composting and soil building information. Articles outlining steps to creating compost and extolling the benefits of composting are common. But they all tend to assume that all composts are equal – that all composts are acidic due to the production of humic acids as they decompose. But are they?

This section was prompted by information presented in a British book (Perfect Plants for Problem Places by Gay Search). It’s not a book about composting, but it is full of composting tidbits worth noting - especially in chapters on gardening in acidic and alkaline soils.

In alkaline soils, Ms. Search cautions, you can’t simply dig a hole, fill it with lime-free compost and plant acid lovers and expect thriving plants forever onward - especially if you water acid-loving plants with water which is alkaline. (Editorial Note: Our local geology tends to give those on local wells alkaline water and just about all municiapl water has its pH adjusted to be slightly alkaline to prevent iron distribution pipes from rusting prematurely.) In a relatively short time the environment around the root hairs tends to revert to an alkaline environment and root hairs of acid-loving plants will become unable to absorb nutrients in the balance essential to their needs. The result: sickly, yellow-foliaged plants soon to wither away. The problem: lack of iron and magnesium. The cure: Add some sequestered iron to your watering can or sprinkle sulphur pellets on the soil and then fork in these nutrients to a depth of a couple of inches. Take care not to injure the plant roots!

In neutral or alkaline soils, Ms. Search recommends mixing your native soil with two of the most acid-yielding composts - pine bark or cocoa shells - to get acidic soils for acid-loving plants. Other composts, such as garden compost, leaf mold and rotted manure, yield less acidic byproducts and you would have to use larger amounts of these to achieve the same shift of acidity. How much compost to add depends on the alkalinity of your the soil. She suggests leaving the soil unplanted for a month and then taking follow-up soil samples. It takes about a month for the soil to reach a stabilized pH from compost additions. It is quite likely that further additions of the appropriate compost will be necessary to get to the desired level of acidity – often a pH of 6.0 to 6.5. (Editorial note: It takes much less time if you use inorganic acidifiers such as pelletized sulfur or ammonium sulphate.) Once the soil is sufficiently acidic, then you plant. It is worth spending this extra time getting your soil right. How much money and effort are you willing to waste on expensive plants that will sicken and die if the soil isn’t right?

She reminds us that organic mulches decompose slowly. When completed, the alkalinity of alkaline native soils will gradually return unless fresh acidic compost is applied on a regular basis. This is usually an annual chore, best done in the spring and may require annual soil tests to monitor your efforts. Keep in mind that if you want garden plants to self-seed successfully, you should delay mulch/compost application until after the soil has warmed up and your seedlings are up and growing. Mid-June is soon enough for mulch/compost application.

Mushroom compost is one of the most widely available composts available in the Ottawa area. But beware of its content and results. We’ve used truckloads of it, in previous years, on vegetable gardens and full sun beds with excellent results. But our developing shade gardens (where many of the plants are wanting acidic soils) never really prospered with mushroom compost applications. I’ve tended to pass off this lack of plant performance as a problem of tree root competition for available moisture. But Ms. Search warns that spent mushroom compost contains lime and therefore tends to create alkaline soil conditions! Obviously I don’t want to go in this pH direction, I want a product which maintains acidic soil conditions. Also another warning from a very bad personal experience - we killed thousands of dollars worth of perennials one year by incorporating mushroom compost into potted plants intended for sale. The mushroom compost was loaded with salt. Investigation showed that the mushroom industry uses mounds of coarse salt to build 'salt mountains' over diseased mushrooms to confine the spread of mushroom diseases. Some crops have problems- others don't. You never know which quality of mushroom compost you'll get in your truckload/bag full. Since that awfully expensive experience we've switched to Sea Shell Compost (which we normally sell) as it has a 'guaranteed minimum analysis label' which mushroom growers are not able (or willing) to provide.