American holly is an evergreen tree native to the eastern and central United States that grows up to 50 feet tall. It beautifies the landscape all year long, particularly in the fall and winter, offering its attractive berries (called drupes) and spiny, green foliage when other plants may be dormant.
Only female hollies have berries; both male and female plants must be present for fruit to form. Hollies provide cover and food for birds and have been developed into more than 1000 varieties (only two of which grow well in Colorado - see below).
Per CSU Extension, only a few hollies are recommended for Colorado if planted in protected sites, but beware that deer browse them heavily in winter. Some hybrid varieties are ‘Blue Boy,’ ‘Blue Girl,’ ‘Blue Prince’ and ‘Blue Princess.’ For these hollies, one male to three female plants must be planted to yield berries.
Native hollies will always flourish better than hollies from other parts of the country. Oregon grape holly and creeping grape holly, the low-growing form, are beautiful all year round - their shiny, spiny, green leaves turn rich burgundy in the fall and remain through the winter; bright yellow flowers delight in spring; fauna enjoy the blue berries. These hollies are tolerant of our alkaline soils, thrive on less water and perform best in partial shade.
Is holly easy to grow in Colorado?
Typical American hollies from eastern U.S., and Chinese hollies, are challenging to grow in Colorado because they prefer a moist and acidic, humus-rich soil. Without a lot of soil amendment and extra water, non-native hollies will not grow to full height and may not perform well in Colorado.
Credit: Farmer's Almanac and CSU Extension