The holly and the ivy,
Now both are full well grown.
Of all the trees that are in the wood,
The holly bears the crown.
The words of the traditional carol, which originated in England in the early 19th century, neatly sum up the enduring appeal of English holly (Ilex aquifolium). While some people may only think of holly as a source of holiday decorations, it is also an excellent, evergreen garden plant.
You can’t beat English holly for its substantial, lustrous leaves and bright berries, both of which stand out, especially in the winter months when color in the garden is hard to come by. Left to their own devices, hollies can grow to be substantial landscape specimens, topping out at 30 to 50-feet tall and half as wide. Pruned to smaller sizes, the plants can fit a variety of situations. Holly hedges, for example, work well in formal garden settings, as well as for boundary plantings. As single specimens, the plants can be left to grow naturally, limbed up into tree form or carefully pruned into formal geometric shapes.
Though best known for its decorative qualities, English holly is also useful for habitat gardens. The tiny white flowers that appear in mid spring are excellent nectar sources for bees, while the berries are favorites of birds and other small animals. Dense branching and leaf configuration means that full-grown hollies can be veritable “bird condos”, providing nesting sites and cover. Best of all, holly is relatively unattractive to the deer that bedevil many gardeners
There are over 400 holly species in the world, and cultivated varieties of English holly are among the best known. The genus name “Ilex” was bestowed upon the plant by Carl Linneaus, and the Ilex aquifolium was described by Linnaeus in 1753. The species name, “aquifolium”, means “with pointed leaves.”
And those pointed, spiny leaves make some people wary of the English varieties. New growth tends to have sharper edges than older leaves, so stout garden gloves are a good idea when pruning or handling holly.
The happiest English hollies grow in USDA Plant Hardiness zones 6b or 7 through 9. Some varieties, like ‘Twenty Below’ are more cold hardy and can be grown successfully in the colder parts of Zone 6, or possibly some parts of Zone 5. At the colder end of the hardiness range, site hollies where they will have some protection from cold winter winds. The plants prefer sun to light shade and grow best in soil that is on the acid end of the pH spectrum. Usually young hollies are available in containers or as larger, balled-and-burlapped specimens. Plant in spring, if possible, in well-drained soil, amended with a high-quality amendment like Fafard® Garden Manure Blend or Black Gold® Canadian Sphagnum Peat Moss. Water thoroughly when installing the holly and continue to water plants in the first few weeks while they establish new roots.
Hollies are dioecious, meaning that shrubs have either female (berry producing) or male flowers. If you want a holly with abundant berries for holiday decorations or landscape color, you will have to act as a horticultural matchmaker. In order for female plants to produce crops of berries, compatible male plants must be planted nearby as pollenizers, preferably within 30 to 40 feet of female plants. Insects, especially bees, do the actual pollination and one male holly can pollinate several females. When you buy female plants, check with your nursery or garden center for compatible male varieties. A few English hollies, like ‘Post Office’, are self-fertile and do not need a companion male plant. The best time to prune holly is in late spring to early summer, but remember that pruning female plants will reduce the number of fall berries. Only prune when it is absolutely necessary for the health and appearance of the plant.
To spice up your evergreen array, use variegated English hollies, like the cream-edged Ilex aquifolium ‘Argenteo Marginata’ and yellow-edged ‘Lily Gold’. These are often somewhat smaller than the species, but they can used in the same ways in the garden. The edges of ‘Lily Gold’ also turn slightly pink in cold weather. Another attractive form is green-leafed ‘Teufel’s Zero’, a female variety with slender, weeping branches and excellent cold tolerance.
As with many species that originated elsewhere and made good in the New World, English holly comes with some caveats. It has been reported to be invasive in parts of eastern and western Canada, the Pacific Northwest, and northwestern California. In these areas, it may be wiser to choose non-berried male selections with exemplary foliage, such as the confusingly named ‘Silver Queen’. This male form has wonderfully dark green leaves edged in ivory.