Blue Diamond Blue Spruce

Blue Diamond blue spruce (Picea pungens ‘Blue Diamond’) – a cultivar of blue spruce. The cultivar was obtained in 1990 in Deurne (the Netherlands) and patented by Nelis Kools (patent number PP19,550) in 2005. It originated from a cross between the female blue spruce Glauca (Picea pungens ‘Glauca’) and an unknown blue spruce cultivar.

It is a slender coniferous tree with a broadly conical crown. The plant reaches 4–6 m in height and up to 2–3 m in diameter. Growth rate is 10–15 cm per year. Branches form regular dense tiers around the trunk from ground level to the top.

Needles are soft, dense, and a beautiful silvery-blue color.

Cones are elongated and light brown.

Hardiness zone: 3 (-40°C).

Location: Prefers full light but tolerates light partial shade. Prefers moist and fertile soil, light or medium loam. The top layer of soil should be well permeable so that the roots receive the necessary aeration. Does not tolerate waterlogging and soil compaction. Has low water requirements.

Planting: The optimal time for planting is late April to late June. Soil mix: turf, leaf mould, sand, peat in a ratio of 2:2:1:1.

Care: Responds well to fertilization. The area around the trunk is recommended to be periodically weeded and loosened, but not dug over. It is also advisable to mulch the trunk circle with peat or loose compost followed by incorporation. During dry periods regular watering is recommended, avoiding complete drying of the root zone, as well as evening overhead watering of the crown. Manure or compost can also be applied in early summer. When grown in polluted locations, it is recommended to wash the spruce at least once a month.

Pruning: Tolerates trimming well, which is carried out once a year after shoot growth has finished. By pinching out the central buds of lateral shoots and shortening the growth in summer, a more compact crown can be obtained.

Diseases: schütte, snow schütte, fusariosis, stem and root rot, bark necrosis, ulcerative (canker) cancer, cone rust, spruce tortrix. Suffers less from spring scorch than other cultivars of Colorado spruce.

Pests: red spider mite, spruce sawfly.

Propagation: Propagated by cuttings, seeds, and grafting. Cuttings are best taken in early June. Winter cuttings without treatment with a rooting hormone root poorly (take rate 45%). For cuttings, take matured lower branches from the mother plant that do not exceed 10–12 cm in length. The cutting separated from the mother plant should have a «heel», otherwise the plant will quickly die. The lower part of the prepared cuttings should be treated with rooting stimulants. Cuttings are planted to a depth of 2–2.5 cm. The substrate should not dry out during rooting, but overwatering the soil is not recommended. For seed propagation, seeds should be pre-soaked in water and sown in spring or autumn. With spring sowing, the first seedlings appear after 14 days.

Uses: Looks striking as a specimen in mixed borders and as a natural spiny hedge along the edges of a plot.