'Blue Princess' holly is the female cultivar of the blue holly group of broadleaf evergreen shrubs, commonly used as landscape specimens and hedge shrubs. When pollinated by its male counterpart, 'Blue Prince,' it produces the bright red berries that we come to associate with holly shrubs in landscape use. These plants are considered Meserve hybrids, developed by amateur horticulturist Kathleen Kellogg Meserve as the hardy standard holly sold in garden centers and nurseries everywhere. This shrub's leaves are a glossy, dark green color with a bluish cast to them and are moderately spiny. Their inconspicuous flowers bloom in spring (and sometimes again in fall,) producing the bright red berries that brighten winter.
|Botanical Name||Ilex x meserveae 'Blue Princess'|
|Common Name||Blue Princess holly, Blue Prince holly, blue holly|
|Plant Type||Broadleaf, evergreen shrub|
|Mature Size||15 feet tall with a 10-foot spread|
|Sun Exposure||Full sun to partial shade|
|Soil Type||Sand to heavy clay; tolerates a wide range of soil types|
|Soil pH||5.5 to 6; slightly acidic to neutral|
|Bloom Time||Spring and sometimes fall|
|Hardiness Zones||5 to 8|
|Native Area||Wide global distribution throughout tropical, subtropical, and temperate zones|
How to Grow 'Blue Princess' Holly
The best time for planting holly shrubs is fall. Spring is also suitable depending on your region. Warmer climates benefit from fall planting, so the plant roots will have a lot of time before the onset of hot, dry summers. Space the plants 2 to 3 feet apart, depending on the variety used and overall size. Because holly shrubs tend to have shallow root systems, add mulch to keep the soil cool and moist.
These shrubs are dioecious plants, meaning they are separated into two sexes. Only 'Blue Princess' can develop the trademark holly berries, and it needs a male pollinator to do that. To determine whether the plant you have is a 'Blue Prince' holly or an unfertilized 'Blue Princess,' examine the flowers, located between the leaf and branch joint. The small clusters of creamy white flowers are similar in appearance, but the difference is that males have more prominent stamens than found on the females.
Grow 'Blue Princess' holly in full sun to partial shade. Also, you will need to protect the shrubs from winter foliage burn. You can do this by avoiding south- or west-facing exposed planting sites. This also helps prevent summer heat stress.
Apply regular deep watering in the first growing season to establish an extensive root system, then continue regular but lighter waterings—weekly, or more often in extreme heat. The plant requires an evenly moist, well-drained soil for optimal growth but will die in standing water.
Temperature and Humidity
The lowest temperatures that this plant can endure is about -20 to -10 degrees Fahrenheit. Consider applying a thick mulch around the root zone in winter to protect it in exposed locations or colder microclimates. This plant prefers somewhat higher humidity than most shrubs.
Minimal fertilizer is required. Too much nitrogen in the soil will keep your holly from fruiting. Use Holly-Tone, a natural organic fertilizer made especially for holly, or a similar product.
Propagating 'Blue Princess' Holly
All species of holly propagate reliably from cuttings taken in late spring or early summer. Seed propagation is not recommended due to the extremely low viability, slow growth rate, and high instance of failure.
Take a softwood cutting about 1/4 inch below a leaf node, then dip the cut end in rooting hormone and embed the cutting in a mixture of potting soil and sand. Keep the cutting moist until a good root system develops, then transfer into a larger pot or plant in the garden.
It is necessary to plant a male pollinator such as 'Blue Prince' holly nearby in order for a female to produce holly berries; however, maintaining a 1:1 male-female ratio is not needed. One male specimen will suffice as a pollinator for several females.
While it is possible for the 'Blue Princess' and 'Blue Prince' holly to top 15 feet in height at maturity, these shrubs are easily kept at a fraction of that height even with just minimal pruning. You can shape these plants to your desired dimensions.
Unless you are using them in a hedge, these plants look best when the pruning is not too obvious. To accomplish this, stagger the depth of your pruning cuts.
The best time to prune holly depends on aesthetics. Some gardeners prune in early winter because they want to bring the cut stems with their holly berries into the house and enjoy them inside. Others prune later in winter because they prefer their display of holly berries outside.
Hollies bloom on old wood—wood produced the previous growing season. So any branches you prune off will result in reduced pollination and fewer flowers and berries the following year.
Toxicity of Blue Princess Holly
Holly leaves, branches, and berries may be beautiful holiday decorations, but the berries are mildly toxic to people and pets. The berries include ilicin, a mildly toxic substance. Swallowing holly berries can cause vomiting, diarrhea, dehydration, and drowsiness. The berries taste terrible, so rare that large quantities are eaten and there are no known fatalities from holly. If you do decorate during holidays with branches, be warned that the berries dry out quickly indoors and those that drop to the floor may be picked up and eaten by curious children and pets. If you have small children or animals, it may be best to avoid using them as indoor decorations unless you are diligent about gathering up the fallen berries.
'Blue Princess' hollies, with their evergreen leaves and trademark holly berries, are fine winter-interest shrubs and certainly attractive enough to serve as specimens in the winter landscape. To ensure optimal enjoyment of these qualities during the long winter, plant hollies near your main entrance, perhaps in a foundation planting. The evergreen leaves also make this a good hedge plant for providing color year-round.
Branches festooned with red holly berries may be pruned before the holidays, so that the clippings can be brought inside and used for decorations.
Varieties of Blue Holly
The "blue" in "blue holly" derives from the degree of dark blue-green tint in the leaves. Two other popular blue holly male-female pairs include:
- Blue Boy (Ilex x meserveae 'Blue Boy') and Blue Girl (Ilex x meserveae 'Blue Girl')
- Blue Stallion (Ilex x meserveae 'Blue Stallion') and Blue Maid (Ilex x meserveae 'Blue Maid')
There are many other types of holly beside the blue variety.
- English holly (Ilex aquifolium) is the holly invested with so much Christmas lore.
- Nellie Stevens is a tree-form hybrid holly popular in the southern U.S.
- Northerners seeking a tree-form holly are better off planting the somewhat hardier Ilex opaca 'Mac's Prince,' a type of American holly.
- You may have seen Hetz Japanese holly (Ilex crenata 'Hetzii') without even knowing it. The foliage of Japanese holly can easily be mistaken for that of boxwood.
- Sky Pencil (Ilex crenata 'Sky Pencil') is holly that assumes an extreme columnar form.
Common Pests/ Diseases
Because hollies prefer acidic soil, they can develop chlorosis (yellowing of leaves) in soil with an alkaline pH. Feeding with an acid fertilizer can counteract this.
Common insect problems include holly leaf miner, spider mites, whitefly, and scale. Disease issues include leaf spot, lear rot, tar spot, and powdery mildew.
Hollies can also be susceptible to leaf drop and leaf scorch.
Comparison with Winterberry
If you do not particularly like the look of evergreen hollies but still desire holly berries, plant winterberry instead. Winterberry is a deciduous bush and its display of holly berries, under the right conditions, is superior to that of the evergreens.