By Mary Perlmutter

In our central Ontario garden, the last week in May is when we usually transplant bedding plants and the seedlings grown in the house under lights. Making a successful transition to the garden means preparing the garden during April. This often involves amending the soil so that the fertility, pH and texture is right for each plant.

Soil which has been treated regularly with compost will have a good humus content with balanced levels of N, P and K as well as micronutrients – especially if the compost has been made from a variety of materials from the kitchen and yard.

Green manure and cover crops can really build up your garden’s fertility. I use legumes to help boost my soil’s N level. When my garden soil was low in phosphorus last year, after harvest I planted two of my vegetable beds with buckwheat, two with annual rye grass and two with red clover. These cover crops all take up phosphorus, and they will be tilled into the beds this spring as soon as the soil is dry enough to work without danger of compaction.

Over the years, my soil has developed a very good humus content from cover cropping, mulching and additional compost. Plan now to plant a cover crop as you harvest next fall! I get my seed in small quantities from William Dam Seeds.

When transplanting my seedlings into the garden in late May, I mix well into each planting hole some of Mel Bartholomew’s "1-2-3-4" Organic Fertilizer: 1 part blood meal, 2 parts bone meal, 3 parts wood ash and 4 parts compost or leaf mold. I find about 250 ml (1 cup) is best for tomatoes and peppers while a quarter cup does the brassicas. I mix this recipe in a plastic container or garbage bag in April so it’s ready to use at planting time. Mel Bartholomew, the author of Square Foot Gardening, assures us that this is a well-balanced all-purpose fertilizer.

The soil’s pH (its acidity or alkalinity) is another thing that I sometimes amend in my garden. Most plants can tolerate quite a range of soil pH before they start to suffer, while others are fussier. My own soil is very alkaline, and when I plant potatoes, which do best in acid soil, I put oak leaves, rhubarb leaves, pine needles and cedar sprays through the mower and line each potato hole before placing the seed potato in and covering it over. The same acidic leaves are used as a mulch all summer on all my beds. In spring, the mulch is tilled into the beds with my little electric tiller. Other plants that prefer more acidic soil conditions are rhododendrons, azaleas, blueberries and cranberries.

On the other hand, asparagus, beans, beets, cabbage, cauliflower, lettuce, onions, parsnips, peas, carnations, geum, iris, nasturtium, phlox and sweet peas love my alkaline soil. Soil which is too acidic for plants like these can be ‘sweetened’ with wood ashes, crushed limestone or dolomite.

Your soil’s texture can affect its drainage, aeration and moisture retention in the root area of your plants. The particles of very sandy soil are large and don’t hold moisture very well. Heavy clay soil is made up of particles so small and close together that they are almost impervious to air and water. Loam, the ideal garden soil, is a combination of these two extreme types.

I have always found that adding humus, in the form of compost, improves drainage and aeration in clay soils and increases water retention in sandy soils. Growing cover crops over the winter can help sandy soil. The best way to modify a heavy clay soil is to add and incorporate sharp builder’s sand. Worm castings or compost should also be tilled into a heavy clay soil along with the sharp sand.

It is easy to ‘strip compost’ clay by digging a small hole each day between plants and putting kitchen scraps (no meat, fish or milk products) directly into the soil and covering immediately with the soil on your shovel or trowel. (You do not want any animal ‘double digging’ your garden, disturbing the root structure of your transplants!)

The more soil preparation I do in April, the easier it is to enjoy planting in May!