Gardening with Shade Plants
I've been gardening in the high desert of New Mexico for more than three decades. And I've gained a healthy respect for the strength and intensity of our sunshine. A shade loving plant in too much sun quickly becomes a puff of smoke. So early on, I found it to be very important to define what sun or shade conditions mean to gardeners here, especially to those who've moved from areas with more benign and less sunny climates.
The intensity of sunshine varies considerably as one moves across the U.S. This is a huge continent with pronounced regional differences in elevation, heat, humidity, cloud cover, and the resulting intensity of the sun's rays. Full sun conditions in Ohio are radically different than in New Mexico. In Ohio, cloud cover is more consistent. Along with the humid, hazy skies, the strength of the sun's rays are greatly diluted by the time they reach the ground, whereas in the high elevation areas of New Mexico, our 300+ days of cloudless skies and lack of humidity and haze fail to dull the strength of our intense sunshine.
Elevation generally has a huge effect on the sun's intensity; the higher above sea level, the stronger the sunshine, and the higher the ultra-violet wavelengths. You don't tan at 7,000 ft. elevation; you burn.
Definitions for Sun or Shade During the Growing Season
In the Western United States:
- Full sun - all day sunshine or a full afternoon of sun.
- Part shade - morning sun and afternoon shade after 12 p.m. Or all day dappled shade under small-leaved trees, such as honeylocust (Gleditsia) or desert willow (Chilopsis).
- Full shade - no direct sun during the day because of dense overhead foliage or buildings.
In the Eastern United States:
- Full sun - 8 or more hours of sun.
- Part shade - up to 4 hours of sun (during any part of the day).
- Shade - little (morning only) or no direct sun.
Bottom line: study the light in your yard and become familiar with when the sunlight hits the ground and plant accordingly.
Favorite Plants for Full Shade
- Deadnettle (Lamium)
- Silver Archangel (Lamiastrum)
- Hardy Plumbago (Ceratostigma)
- Miniature Mat Daisy (Bellium)
- Rocky Mountain Columbine (Aquilegia caerulea)
- Turk's Cap Siberian Lily (Lilium pumulim)
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Favorite Plants for Partial Shade (Morning Sun or Dappled Shade)
- Soapwort (Saponaria)
- Golden Columbine (Aquilegia chrysantha)
- Little Treasure Columbine (Aquilegia chrysantha v. chaplinei)
- Coral Bells (Heuchera)
- Western Wood Lily (Lilium philadelphicum)
- Bluebells (Campanula)
- Siskiyou Blue Festuca Grass (Festuca)
- Scarlet Hedgenettle (Stachys coccinea)
- Marion Sampson Monardella (Monardella)
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Some Miscellaneous Factors that Affect Plants and Sun Intensity
Variegated Plants - Plants with variegated foliage will always need less sun that the same species with green leaves. So variegated plants will do best in part sun, dappled, or full shade.
Hot Summer Weather - When day temperatures begin to regularly exceed 90◦F, many plants will benefit from afternoon shade.
New Homes - In new housing developments, sunlight conditions will change over time as trees mature. What was once a sunny spot may gradually change to part or full shade conditions. So plant for current sunlight conditions and understand that in five or more years, you may need to change out your plants as conditions become more shady.
Sunny Winters in Cold Areas of The West - During winter, the sun is lower in the sky, and the angle of the sunlight shifts. This can change a sunny location into a shady location. This is an important consideration for broadleaf evergreen plants in cold climates. Too much sun during Western winters can result in burned foliage. High intensity sunshine combined with frozen soil prevents the foliage from transpiring (losing moisture through the leaves to cool the plant). So be sure plant your broadleaf evergreens and evergreen perennials, such as Helianthemum (Sunrose), in a spot where they are more shaded during the winter.
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