To determine the number of individual plants needed for the massing, you first have to determine the area of the space to be planted based on the general shape of the planting bed. I apologize in advance, because there will be quite a bit of math in this post.
If it’s been a while since your last geometry class, determine the area (square footage) of the space to be planted using the formulas for each of the respective shapes shown below:
Once you have your total square footage to be planted, you
need to know the mature spread (width) of the plant species you will plant in
that space. A plant's size at the time you buy it will not be the same after a few months, or even weeks, of growth. You need to take that growth into account. The plant's mature size information is often
listed on plant tags in nurseries or garden centers, or you can look it up
(plant information). The mature spread
of the plant is how far apart you should plan on spacing the centers of plants from each
other so they have room to mature and not look overcrowded.
|Area of a square or rectangle = length (L) x width (W)|
|Area of a triangle = 1/2 [length (L) x width (W)]|
|Area of a circle = 3.14 (Pi) x [radius (R) x radius (R)]|
|The area of plantings wrapped around the base |
of taller plants can be calculated as a curved rectangle (L x W)
|View of the top of a plant from above|
Once you’ve determined how far apart to space the plants, find the corresponding division factor for that spacing from the listing below:
4” - 0.11
6” - 0.25
8” - 0.44
10” - 0.70
12” – 1.0
15” – 1.56
18” – 2.25
24” – 4.0
30” – 6.25
36” – 9.0
Divide the total square footage to be planted by the division factor, and the result is the quantity of plants needed to fill your area at that particular plant spacing. For example, if I need to plant 50 square feet with plants evenly spaced 18” apart: 50 / 2.25 = 22 plants.
These factors assume a triangular plant spacing, which provides a more dense and full appearance than square spacing.
Now that you’ve invested all this hard work figuring the
quantity of plants to perfectly fill your planting bed, be sure to maintain the
same discipline when planting them. By
that, I mean use a tape measure ensure your spacing is correct and consistent
during installation. If you try
eye-balling it, you’ll probably end up with too many, too few, or unevenly spaced
plants when you reach the end of the planting bed.
|Division factors are based on triangular plant spacing.|
|Square plant spacing does not look as full and dense as triangular spacing.|