Wednesday, May 23, 2012


            Fitzgeralds Gardening is busy these days, too busy for me to keep all the balls I’m juggling up in the air. We’re supposed to be working for a client right now, digging up her winter gardens and containers and setting up the summer show; instead, here I sit, enjoying the air-conditioning, typing away.

            I’d like to tell myself it’s because Tim hasn’t brought me my second cup of coffee yet, but that’s pretty lame: I’m sitting as close to the coffeepot as he is. Besides, cup numero dos just arrived.

            Actually, the reason for the circuitous path this post is taking is the Benadryl I’m scarfing down like peanuts to take the edge off the itch of my first significant case of poison ivy this season. Unaccustomed as I am to popping pills, antihistamines make me even less focused (read “stupid”) than usual. Never a revved–up go-getter at the best of times, I’m currently reduced to the status of a muddy puddle. (Why a muddy puddle? Because I like the way the words sound, that lovely assonance. Have I mentioned I’m a poetry reader?)

            Anyway. In an effort to convey some useful information, I’ve copied and pasted, in its entirety, Chapter 20 of my excellent but sadly unpublished book, modestly titled The Best Gardening Book Ever. I find the strictures of mathematics and whimsy of doodled illustrations soothing in my current addled state. With no further ado…


In the course of gardening events, it often becomes necessary to ascertain the square footage of an area in order to accurately estimate the amount of mulch or soil amendments you need. Occasionally a familiarity with calculating perimeters helps too, like when your wife sends you to Lowe’s to get enough edging for that new bed you’re going to dig when you get back. Yes, ninth- and tenth-grade math classes recessed long ago, but you’d be surprised at what Mrs. Tillinghast and Mrs. Taback managed to brand on your brain.

Area, or square footage, of any rectangle is simply length times width: A[rea] = ab; P[erimeter] = 2a + 2b. In the real world, however, gardening projects are seldom rectilinear. One strategy is to roughly block the space into contiguous rectangles and add the various areas together. This works okay if pinpoint accuracy isn’t too crucial.
Circles are another common bed shape. Remember pi? A.k.a. 3.14…, symbol π? (My youngest son has pi memorized to about a hundred places. On our first trip to New Zealand, as the plane sat on the tarmac in Auckland, four persons in spacesuits entered the fuselage and emptied the aerosol cans they carried all around the passenger compartment as we sat there, stunned and trying not to breathe. It was not a particularly welcoming experience, although it may explain why Sam, who was three months old at the time, turned into a genius. He certainly didn’t get it from his parents.) It—pi, not the charming Kiwi disinfect-the-foreigners ritual—comes in handy here. Where r = the radius of the circle, A = πr² and P = π2r.  

            Triangles occasionally come into play as well. Where b = base of the triangle and h = the height, A = bh/2 and P = a + b + c.
Alas, most garden beds are actually kind of blobby. To get an excellent estimate of an amoeba-shaped space, try this formula I stumbled upon in an issue of Fine Gardening years ago and have been using ever since. It goes like this:

Make a drawing of the space you need to know the area of—to scale if you’re not outside taking on-the-ground measurements.

Draw a straight line through the longest dimension of the bed; label the end points A and B.

Divide AB into segments of equal length. In our example, AB = 27’. I divided it into 3-foot segments (you could also use 9-foot segments, but there will be three times as many three-footers, giving a more accurate picture of the bed).

Measure the width of your bed at each segment-point perpendicular to AB. Label the line running through point A as S1 and continue on through to point B, which in our example is labeled S10. I know this is confusing. Just look at the next sketch.

Now it’s formula time. L = the number you divided AB by and S = the length of the perpendicular lines through the segment points. The formula is:

Area = L/3 [(SA + SB) + 2(S3,5,7…) + 4(S­2,4,6,8…)]

            In our example, the area works out like this:

A = 3/3 [(3 + 5.5) + 2(10 +10.5 + 16 + 17) + 4(9 + 9.5 + 12.5 + 18.5)]
A = 1 [8.5 + 2(53.5) + 4(49.5)]
A = 1 [8.5 + 107 + 198]
A = 1 [313.5]
A = 313.5 square feet, round up to 314 square feet

I don’t know why, but this formula provides amazingly accurate results. And, after the first time you use it, you’ll know the area of that oddly shaped bed in less time than it took to read this explanation.

            Once you’ve figured out the area of your bed, divide it by the number of square feet a unit of mulch/soil amendment covers based on the estimates below:

·         a 3-cubic-foot bag of pine bark nuggets covers about 10 square feet to 3 inches deep; a 2-cubic-foot bag, about 7 square feet

·         a 3-cubic-foot bag of shredded hardwood covers about 15 square feet to 2½-3 inches deep; a two-cubic-foot bag, about 10 square feet

·         an average-size bale of pine straw covers about 40 square feet to 3-4 inches deep (it’s fluffy by nature)

·         a 50-pound bag of Black Kow covers about 20 square feet to 1-1½ inches deep

(To mulch the blobby bed example above, I’d need 55 2-cubic-foot bags of pine bark nuggets, or 314 ÷ 7. Always round up.)

When edging, the following approximations will help you determine how much material you’ll need once you’ve determined the perimeter:

·         For standing-brick edges: measure how many units comprise a linear foot (bricks are usually three inches wide; ergo, 4 bricks = 1 foot) and multiply by the number of linear feet in the perimeter.

Rough estimates for various other materials:

·         1 ton of rip-rap ≈ 85 linear feet of edging

·         1 ton of widely spaced flagstone ≈ 64 linear feet of two-foot-wide path

·         1 ton of closely spaced flagstone ≈ 46 linear feet of two-foot-wide path

·         1 ton of wall stone (I’m talking veneers here) ≈ 50 linear feet of wall to 8 inches high

Now get out there and make your high school math teacher proud.

[End of Chapter 20.]

            This is as helpful as I can be this week, under the circumstances. I’m going cold-turkey on the Benadryl: by next week it will have cycled out of my system.

            Thanks for dropping by. Itchily yours,


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