Taken from Eclectic Gardener @ www.teachinggarden.org
Written by Alan Hickman

After I’d sent off the column two weeks ago, it occurred to me that asking for questions to which readers couldn’t find answers in books was a rather risky invitation. Not only that, the request also had a passing resemblance to the advertisement, allegedly posted by a literacy organization, which said ‘If you can’t read this notice please call 416-...- .... to learn how.’

As it turned out, there wasn’t an avalanche of questions like ‘Why is the pH of pure water 7? Why isn’t it zero or some sensible number?’ What did come in were questions which continue to vex gardeners even though they have been answered many times by many people.

Fully half of the questions received related to lawn issues of one sort or another. Typical questions were: ‘Why has my backyard grass turned to weeds and clover?’ ‘I need to build a thicker denser lawn in my front yard and I’ve tried various things over about 7 years but it’s still not where I’d like it to be.’

It happens that lawn grass is very much on my mind at the moment. A few days ago, I was told that I was hosting a garden party at the end of the month. Just one small problem, after fifteen years of almost total neglect, I don’t really have a garden! What used to be lawn is solid Polygonum aviculare.
After the mower has gone over it, five hundred square feet of creeping knotweed really don’t look that bad - from a distance - and the dogs pee on it quite contentedly, but it definitely isn’t a ‘garden party’ lawn.

There is only one reason that weeds take over a lawn; the weeds like the prevailing conditions more than does the grass. The grass simply gets out competed. To have a lawn that looks like a golf course, the grass needs to have the conditions found on a golf course.

If a lawn is not looking its best, then consider what is above the grass and what is below it. Lawn grasses prefer full sun. So-called ‘shade mixes’ may be somewhat more tolerant to being in the shadow of a building or a tree for a few hours a day, but they are still grasses and grasses are at their best on prairies. On prairies, the only shadows come from the occasional passing buffalo. Every hour of sunlight lost is an hour’s advantage given to some unwanted broadleaf weed.

If the light is adequate and the grass does not thrive, then likely the plants don’t have happy roots. Like most vegetation, grasses prefer light loam soils; soils which have those seemingly opposing properties of being free-draining and moisture-retentive. Generally speaking, Brampton gardens do not naturally have light loam soils; they are usually, at best, heavy clay loams or, more likely, some sticky substance better suited for making bricks than for growing grass.

By definition, a loam soil contains equal parts of coarse sand, fine sand, silt and clay. Local soils tend to be missing the coarse and fine sand fractions. The result is soil which puddles in heavy rain, has poor gas exchange and which compacts as it dries.

It should be noted that there is no mention of organic matter in the definition of loam. Loams are distinguished entirely by the ratios of their mineral components. Contrary to popular wisdom, adding peatmoss and compost will not change the underlying properties of a clay soil. A fertile agricultural loam will typically contain only three to five percent organic material. Home flowerbeds can have much higher organic contents than 5% and still bake hard in summer.
My excuse for a ‘lawn’ lies mostly under the canopy of a sixty-foot tall maple tree, and it is underlain by forty years’ accumulation of heavily composted clay. Perfect conditions for knotweed among other things.

As I write, half of the area has been hand dug and stripped of weeds. With luck the other half will get done this afternoon. I’ll spread and dig in an inch of coarse sand and, by the time this column gets printed, the sod should be laid. With a bit more luck, the weather doesn’t get too hot, and I throw sufficient water at it, the lawn might be serviceable enough for use in three weeks.

As the idea of hand digging an entire lawn is not likely to enthuse most readers, a more piecemeal approach is an option. Buy one strip of sod (24" x 54") and one blue-boxful of coarse concrete sand (about two cubic feet). Pick the worst part of the lawn and mark out a square, three feet on each side.

Using a sharp spade, cut the existing sod and remove the soil beneath to a depth of 4" - measure it, don’t guess. If you have one, run the removed soil through a 1" sieve and remove any bits of weeds and stones. If you don’t have a sieve, just hand pick the soil and break up any lumps as best you can.
Dump the soil on the drive or on some hard surface, dump the sand on top, and mix the two together thoroughly. Put the sand soil mix back in the hole, an inch at a time, and compact each layer as it goes in. Fill the hole a little higher than the surrounding soil to a allow for settling. Cut the strip of sod into three pieces (1 x 24" x 36" and 2 x 12" x 18") and lay it over the amended soil.

Use some of the of sand/soil mix which is left over, to blend in the edges of the newly laid sod and spread the remainder as a thin top dressing on the rest of the lawn. Thoroughly soak the area with an open hose and don’t walk on it while it is wet.

The omission of any mention of fertilizers and organic soil amendments etc. is not accidental. All that is needed is a strip of sod, (less than three bucks) and a box of sand. (If you go to Salisbury Garden Supplies,12321 Dixie Road, just north of Mayfield Rd. and mention this column, they’ll charge you two Twonies. Take your own blue box and a shovel.)