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Grass #2 of 4
by Dan Clost
by Dan Clost


First serious garden earned 25 cents from the Kemptville Horticultural Society when I was 12. Have been poor in horticulture ever since but rich in spirit.

Went to work writing the Good Earth column (over 500 articles published in newspaper, magazine, website and journal.) and learned that what was printed wasn't what I wanted to say and certainly not what Gentle Reader understood me to say. Subsequently have developed a certain clarity and economy of words.

Day job- nursery and production manager for a large nursery/garden centre
Side job- Garden restoration and renovations, design consultations, remedial pruning.
Night job- garden writer and communicator (overnight success in another 20 years)

Dan gardens in Canadian Zone 5b

June 23, 2002

We're on to lawn management these days. Perhaps, given the interesting start to this year's growing season, we'll look at watering first. How much? When is the best time?

There is absolutely no doubt in my mind that this is a contentious area. Here are a few points to make before embarking on this journey. The first is that the recommendations made here will try to reflect the grass' natural patterns of moisture uptake. The second point is that we are discussing our lawns- not golf courses, sports fields or other intensively cultivated swards. If you're the sort who can wade through dry, technical stuff then Turf grass Management by A.J. Turgeon is a book for you. It focuses on commercial management but, by golly, if you can understand this one you will know everything you ever need about how grass does its thing. Visit your library and if this book isn't available then use the interlibrary loan system. It is worth the effort.

Perhaps the most important consideration is the understanding that we are not really watering the grass. We are putting adequate moisture into the soil so the plant will be able to access it when needed. So now we get to discuss amounts of water. Let me equivocate and say as my new friend Paul (Erik) Voskamp would, "It depends." Commercial measuring instruments look at moisture content at 2" and 6". The 2" depth, if used as a bellwether, is likely to be for intense management. The 6" depth is apt to be used in those mythical areas where there is actually real soil that deep. I live in the west end of Trenton, Ontario: gravel starts at the 3" mark and changes to boulders at the 4" level. Yes, that is an exaggeration but if you had your front lawn dug up and turned over three times in four years (water, sewer and water again) you might feel that way too. Perhaps the easiest way to determine the amount of water needed is to use the shovel method. Push it into the lawn, pry over just enough to expose the soil, and take a look. Are you satisfied with the depth of infiltration? Not a scientific method but it works. After a few times you'll get an idea of how long to water using your system. Here's the real reason for a less than specific answer: watering rates depend on soil composition, substrates, thatch, type of grass, exposure to elements such as wind and sun, soil and air temperatures, slope, traffic, and so on. Every lawn is different.

Aim for 2" to 3" of visible dampness. There will still be water moving through the soil and will easily "fill up" the next several inches. The point is to encourage the roots to move into this zone; incidentally, an area that some weeds, especially broad leaf plantain, Plantago major, have difficulty reaching.

Another time for watering the lawn is during exceptionally hot weather when grass blades begin to wilt. The plant is unable to move enough moisture into the blade to keep up with evapotranspiration. In this case, wilting is similar to sunstroke and our job is to cool down the grass. For this type of application it is best to set your sprinkler or nozzle to a fine mist. Do not let water puddle on the surface or you may wind up with scalded plants, no fooling.

Before we leave the quantity issue, there is one more consideration- rate of application. It may seem obvious but don't apply water faster than the soil can absorb it. The water does not run off because the ground is full. In fact, below that top 2", the ground can be very dry even if you have been letting the water flow for a lengthy time. Trickle irrigation systems are best because of their slow rate of application amongst other reasons. Next week- when to water, how to mow.


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