How to Grow Blue Princess Holly

Blue holly berries

The Spruce / David Beaulieu

Blue Princess holly (Ilex × meserveae 'Blue Princess') is the female cultivar of a blue holly evergreen shrub. It's commonly used as a landscape specimen plant and hedge shrub. When pollinated by its male counterpart, 'Blue Prince,' it produces bright red berries in the wintertime. It's one of the many holly plants that can be used as a winter holiday decoration. Blue Princess' leaves are a glossy, dark green color with a bluish cast to them, and they are moderately spiny. Its inconspicuous flowers bloom in the spring (and sometimes again in fall).

This shrub has a moderate growth rate. The best time for planting is in the early fall. Spring is also suitable for planting depending on your region. Warm climates benefit from fall planting, so the roots have time to develop before summer heat arrives.

Botanical Name Ilex x meserveae 'Blue Princess'
​Common Names Blue Princess holly, blue holly
Plant Type Shrub
Mature Size 10–15 ft. tall, 8–10 ft. wide
Sun Exposure Full, partial
Soil Type Moist, well-drained
Soil pH Acidic, neutral
Bloom Time Spring
Flower Color White
Hardiness Zones 4–7 (USDA)
Native Area Hybrid
Toxicity Toxic to people and pets

Blue Princess Holly Care

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 females. To get the berries, you should have at least one male per three to five female shrubs.

When planting, add a layer of mulch to keep the shallow roots cool and to retain soil moisture. Besides making sure your shrub is getting enough water and doing a bit of pruning, this is a fairly low-maintenance plant.

Light

'Blue Princess' holly will grow in full sun to partial shade. In the warmer parts of its growing zones, it should have protection from harsh afternoon sun.

Soil

Well-drained soil is key for these shrubs. They can tolerate a range of soil types and prefer a slightly acidic to neutral soil pH.

Water

Deeply water on a regular basis to keep the soil evenly moist (but not soggy) in the shrub's first growing season. This will establish an extensive root system. After that, weekly waterings will typically be fine if you haven't had rainfall, though the shrub might need more frequent waterings in extreme heat. Just make sure it's never waterlogged.

Temperature and Humidity

The lowest temperatures this plant can endure are about -20 to -10 degrees Fahrenheit. Prolonged exposure to unseasonable heat or cold can weaken or kill it. Mulch can help to insulate the roots against temperature extremes. It's also ideal to plant the shrub somewhere that is sheltered from harsh, drying winter winds. A moderate humidity level is ideal.

Fertilizer

Minimal fertilizer is required for this shrub. In fact, too much nitrogen in the soil can keep Blue Princess from fruiting. Use an organic fertilizer made especially for holly, following label instructions. It's also beneficial to mix compost into the soil at the time of planting.

Blue Holly Varieties

The "blue" in blue holly derives from the blue tint of the dark green leaves. Besides Blue Princess and Blue Prince, there are several other female and male blue hollies, including:

  • Blue Girl (Ilex x meserveae 'Blue Girl'): This holly is notoriously hardy, growing in zones 5 to 9. It reaches around 6 to 8 feet high and produces bright red berries. 
  • Blue Boy (Ilex x meserveae 'Blue Boy'): This is the male counterpart to Blue Girl. It won't produce berries, but its dark foliage works well as a dense hedge.
  • Blue Maid (Ilex x meserveae 'Blue Maid'): Blue Maid is a fast-growing holly shrub that reaches around 8 to 10 feet high with a 6- to 8-foot spread. It also produces red berries and is hardy in zones 5 to 9.
  • Blue Stallion (Ilex x meserveae 'Blue Stallion'): Blue Stallion is a fast-growing male pollinator hardy in zones 5 to 9. It grows to around 10 to 12 feet tall, and its foliage is a shiny dark blue-green.

Pruning

While it is possible for Blue Princess holly to reach 15 feet high, these shrubs are easily kept at a fraction of that height with just minimal pruning. 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 indoors to use as decorations. Others prune later in the winter because they prefer their display of holly berries to be outdoors on the shrubs.

Unless you are using them in a hedge, these shrubs look best when the pruning is not too obvious. To accomplish this, stagger the depth of your cuts. Hollies bloom on old wood—wood produced the previous growing season. So note that any branches you prune off will result in fewer flowers and berries the following year. Balance this factor with your desired size and shape when choosing how much to prune.

Propagating Blue Princess Holly

All species of holly propagate reliably from cuttings taken in the late spring or early summer. Seed propagation is not recommended due to extremely low viability. Take a softwood cutting about 1/4 inch below a leaf node. Next, dip the cut end in rooting hormone, and embed the cutting in a mixture of potting soil and sand. Keep the growing medium moist until a root system develops. Then, transfer the new plant into a larger pot, or plant it in the garden.

Common Pests/Diseases

Because hollies prefer acidic soil, they can develop chlorosis (yellowing of the leaves) in soil with an alkaline pH. Feeding with an acid fertilizer can counteract this if you have highly alkaline soil. Common insect problems include holly leaf miners, spider mites, whiteflies, and scale. Disease issues include powdery mildew and leaf spot.