Many of our posts here are simply topics we research a bit, and then share the info with you. The assumption is that whatever we feel curious about is something somebody else might too.
Fall is the best planting season for shrubs and trees, hence this post on exposure. (Generally, I would never advise planting anything without an overall plan. I have learned from many landscape errors and I wish I had the money back from all of them. Learning is expensive.)
Plants do not thrive without a climate (of course), a soil they prefer, an exposure they prefer, the duration of sunlight they prefer, or the amount of moisture they prefer.
"Exposure" means the amount and direction of direct sunlight, or the lack thereof, on a given spot during growing season. Only a plant in the middle of a large field or large lawn has no limiting exposure. That is known as "Full Sun," 7+ hours of direct sunlight. Full sun is what is needed for vegetable gardens, hayfields and other farm crops, most trees, and many perennial plantings.
In most of the US, trees and buildings determine the exposure of a planting site. Before you plant anything or put in a garden, you need to determine the exposure and the hours of direct sun the spot gets. For example, an Eastern Exposure location gets direct morning sun for maybe 4-5 hrs. That is known as "Partial Sun" aka "Partial Shade." Many plants love that eastern exposure such as Dogwoods, Hydrangeas, Rhododendrons. Such plants hate the afternoon intensity of a Western Exposure so their Partial Sun needs to be morning.
OK. Before planting something, we need to determine the exposure and the amount of direct sunlight. There's another sun consideration too, though. As this site notes:
Remember that the sun changes position in the sky throughout the year, so an area that is mostly shade in spring and fall may get more intense sun during the summer when the sun is high. This could lead to your sensitive shade plants being burned by the sun in July and August. You don’t want that so be sure to take this into consideration when planning a garden area.
As you move towards more northern latitudes, the angle of sun varies seasonally, expanding and contracting exposure. A couple of my Western Exposure rhododendrons only get afternoon sun for several weeks in midsummer, and even that is too much for them. They survive but do not thrive. If they had afternoon "Dappled Shade," they would be fine. Which brings us to Dappled Shade and other definitions. Some good definitions from here:
Full Sun: Fun sun means 7-8 full hours of direct sunlight during
summer. Those hours could be from 8 – 3 or 12 – 6; anytime during the
day. These hours can also be three morning hours, plus three afternoon
hours.
Partial Sun / Partial Shade: These two terms are often
interchangeable to mean 3-5 hours of direct sunlight each day. While the
terms are interchangeable, there is a default understanding. Partial
shade typically refers to morning and early afternoon sun, while a plant
listed as partial sun, relief from the intense late afternoon sun is
needed. This shade could be from a structure or the shade from an old
oak tree.
Dappled Sun: Dappled sunlight is my favorite kind of sun, if I had to
choose. Dapple sun is similar to partial shade. The plants are getting
partial sun as it makes it’s way through the branches of a deciduous
tree. Woodland plants and under plantings, even for many mosses, prefer
dappled sunlight more so than partial shade.
Full Shade: Full shade means less than 3 hours of direct sunlight
each day, best if it’s morning light. But even in the absence of direct
sunlight, full shade can be a bright light. Plus, full shade likes a
filtered sunlight the remainder of the day. Every plant needs some sun;
even those that thrive in full shade.
So Full Shade is like a Northern Exposure: little to no direct
sunlight. Same as under a large Maple. Less densely-leafed trees can
give the dapple.
A Southern Exposure, assuming no major shading things, means
pretty-much full day sun. A Western Exposure typically takes only the
brutality of the heat and sun intensity of afternoons. That can be tough
on some plants.
Eastern and Western Exposures are roughly half-day sun, ie Partial Sun or Partial Shade.
In real life, few spots have any pure N/S/E/W exposure without
variables like tree shade, building angles, etc., but the point is to
design by exposure, timing of exposure, and duration of exposure, and to
select plantings accordingly.
Some examples I have been considering lately for various purposes:
Red Oak, Holly - Full Sun
Hydrangea and Rhodys: Eastern Exposure or Dappled (but ssome Paniculata types can do great in full sun)
Hosta: Northern Exposure
Western Exposure: Always challenging when the only direct sun is afternoon.
Dappled: Azalea
