When I first read about Hummingbird Summersweet shrubs (Clethra alnifolia 'Hummingbird'), I knew I wanted to find a place for them in my garden. These graceful three-foot mounds bloom in July with tiny flowers packed into sweet-smelling, fluffy cones that attract butterflies and hummingbirds. In autumn, their spare, elegant leaves turn bright yellow. Their open forms don't sucker and need no routine pruning.
They sounded like they would provide a lot of appeal for little effort. All they required was a moist, partly shaded location with somewhat acidic soil.
I planted five baby 'Hummingbirds' under my Jack Pine tree, which lets in a lot of light through its airy canopy and drops needles that keep the ground acidic. When I stopped watering them daily, the shrubs' leaves turned an unhealthy brown-yellow and began to drop.
After spending some time looking at the new shrubs and pondering, I noticed that the pine tree filtered the morning and midday sun, but didn't block any of the intense afternoon sun. Maybe the area was drier and hotter than I'd first thought.
I dug up the five Summersweets and moved them to a shadier area under some Amur Maples on the east side of the house, where they received a few hours of midday sun. When I watered them, all but one perked up, but as I tried to let up on watering, leaves again started falling.
I poked a finger into the soil around the little guys and it came out dry. I did the same test at different times over the next couple of days. Always dry. When I'd planted the maples a few years before, the soil had been perpetually damp. They were supposed to dry out the area to guard our basement from seepage, and I hadn't realized they were doing such a fine job.
I transplanted the four remaining Summersweets to the back of the house. The sun only shone there during the middle of summer, and I suspected the soil was slightly alkaline, but it was the wettest place in the yard, a low spot with thick clay soil.
The shrubs slowly made new leaves and even grew a bit during the next couple of years.
That's how I learned that I didn't know my garden's microclimates, not well enough to choose the right spot for a plant on the first try.
A microclimate is an area of your property with unique environmental characteristics. What makes one microclimate different from another? Three key factors are soil moisture, light, and soil acidity.
Here are some possible light exposure patterns:
Soil acidity is measured on the pH scale. A lower number equals higher acidity, and because the scale is logarithmic, each number is ten times more acidic than the number above it. Neutral pH is 7, and plants vary in their tastes and tolerances. Many traditional garden plants, including lawn, are happiest with a soil pH near 6.5.
Soil acidity is influenced by local sources of acidity (like many evergreens) or alkalinity (such as limestone). Though there are both manufactured and naturally occurring substances that you can use to change your soil's acidity, you can avoid a never-ending battle against your site's personality by choosing plants that will enjoy the soil your site offers.
If you garden for more than a year or two, you may find yourself taking up plants and moving them to areas you think they'll like better. Experimenting with and observing your plants will teach you about your land's unique variations in soil moisture, light, and soil acidity. You can use this knowledge to assemple communities of plants that are well adapted to your garden's microclimates.
LessLawn articles about specific microclimates :
Learn to design satisfying combinations of plants.
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