Measuring Sunlight in Your Landscape

When you are perusing plants at the local garden center, the first thing you should do is look at the tag to see if it’s a good fit for your garden. It’s amazing how much useful information those tiny pieces of plastic contain: annual or perennial, height, width, growing zones, bloom season, watering needs, days to maturity, and–perhaps most importantly–required light levels (sometimes also labeled “placement”).

Though the terms describing light levels in the garden–“full sun,” “part sun,” and “full shade”–seem straightforward, it’s important for the health of your plant that you understand what each means and how to tell where in your garden each condition is met.

Full Sun

Full sun means six or more hours of direct sunlight a day. Usually, full sun areas have continuous sunlight from at least 10 a.m. to 5 p.m. every day of the growing season. Familiar full sun plants include:

• Lavender
• Butterfly Bush
• Black-eyed Susan

Full Shade

Full shade is just the opposite, an area in your garden that is in complete shade for at least six hours a day. The ideal full shade situation gets a little sunlight first thing in the morning but is shielded as the day grows hotter. Favorite full shade plants include:

• Rhododendron
• Impatiens
• Primrose

Part Sun

Part sun is three to six hours of light or filtered light per day. Sometimes “part shade” will be used to refer to plants that enjoy the sunnier side of that spectrum and “part sun” for those that are closer to shade-lovers. Some popular part sun plants include:

• Fescue
• Cardinal Flower or Lobelia
• Burning Bush

Tips to Figure Out Light Exposure

Map Out Your Different Planting Spaces

Be aware that even a very small garden, depending on the placement of trees, walls, and structures, can have a variety of plots with different light conditions, from full sun to full shade.

Note the Light Every Hour

For each of these spaces, start at sun up, and every hour, record how much light the area is receiving:

• Full Sun
• Filtered or Dappled Light
• Full Shade

Time of Year Matters

Unless you’re on the equator, the sun’s path from east to west is going to vary from season to season, and what’s in full sun in the winter may be only partial sun in the summer. Also, it’s hard to get an idea of how much sun your trees are blocking out until their leaves have come in completely the late spring. It’s best to measure your garden’s light levels during the growing season. Usually that means summer but for some plants could include early spring.

Pro-Tip: If you assess the wrong type of light exposure, never fear. Simply dig up the plant and move it to a new location with the correct amount of sunlight.

Plants aren’t all that different than people when it comes to real estate. You wouldn’t expect a city party girl to be happy in an isolated country cabin, or the deep woods hermit to thrive in a crowded high rise. Similarly, shade-loving impatiens will burn to bits in a full sun location while the sun-hungry black-eyed Susan will wilt and die tucked against a north facing wall. Understanding the terminology used to describe light in the garden and how to measure light around the garden will guarantee that you place your plant in the perfect spot, every time.

Once you know the sun exposure, use the My Garden Life Plant Library’s advanced search feature to search for plants by their light requirement.