Hydrangea macrophylla 'Nachtigall'

Compact, bushy, deciduous shrub that grows up to 1.5m tall.

Large lacecap flower heads of tiny dark blue flowers surrounded by pure white florets during summer. The lush leaves are broad and green with serrated margins.

Grow in moist, well-drained soil in full sun or partial shade. Can endure harsh winter cold and is drought-resistant. Although hydrangea can be grown in full sun, the flowers of white and blue cultivars are prone to burning.

Always choose healthy, well-grown plants. Plant after autumn rains when the soil is moist and warm, allowing trees and shrubs to become established before winter. Planting success is often improved on clay soils by adding extra topsoil and forming raised beds. Incorporate coarse sand, bark and compost to improve soil structure. Before planting, ensure that the root ball is saturated and remove planter pot with minimal root disturbance. Trim any broken roots or branches and plant at the same level as in the container. Long term, slow-release fertilisers may be added at this stage. As soil is placed in the prepared hole, tread firmly to bring soil in close contact with the root ball. Water thoroughly, making sure that moisture penetrates to the depth of the root ball.

Planting too closely leads to spindly growth, poor flowering and eventual decline. In a well-planned border, flowering plants should just touch each other to create a full effect without overcrowding. Plant approximately 1m apart.

Apply mulch annually to suppress weeds and conserve moisture. Organic material, such as sawdust and bark, contribute to soil structure. However, make sure to keep mulch away from plant stems. The first summer and autumn after planting are critical for young plants, so water thoroughly during dry periods. A light application (50g/m2) of general-purpose fertiliser in spring is beneficial. Sprinkle evenly and work into the top 2 to 3cm of the soil, taking care not to damage surface roots.

Prune off any old flowers after flowering. Delay pruning until the danger of frost has passed, as the spent flowers and leaves protect buds from damage. All canes that have flowered and thin, crowded and damaged shoots should be cut to the base. Leave shoots which have not flowered, as these will flower next season. Check regularly for pests and diseases, which can have serious debilitating effects on young plants.

Flower colour is affected by soil acidity (pH). Acid soils produce blue flowers and alkaline soils pink flowers. White flowers are unaffected. Most Auckland soils are acidic. Therefore, blue flowers tend to predominate. In early spring, the blue colour may be intensified by watering plants with a solution of 44gm of aluminium sulphate in 9 litres of water. Use the same solution for container-grown plants. Coastal gardens with deposits of shell in the soil are usually alkaline, producing pink flowers. The pink colour can be intensified with applications of lime in autumn each year. Heavy applications of lime up to 500g/m2 can be applied to change blues to pinks. Such efforts usually result in intermediate purplish tones rather than a clear pink. Grow plants in containers using an alkaline potting mix for pinks and an acid mix for blues.

Attracts bees and pollinators.

Most of the time hydrangeas are trouble-free however occasionally they can suffer from grey mould, slugs, powdery mildew, rust ringspot virus and leaf spots. If grey mould is a problem keep humidity low and remove the plant or affected plant parts. For powdery mildew spray with baking soda solution. Rust remove fallen leaves or use more resistant cultivars. Virus affected plants should be removed and burnt.

Camellia Garden