Hydrangeas or hortensias will bring a touch of nostalgic charm to the garden with their exquisite, show-stopping blooms held above crisp saw-toothed leaves on tall stems. From mid to mid-autumn, these long-lasting plants native to Asia and America will reward you with sumptuous, dense foliage and exquisite heads packed with small, delicate flowers. Interestingly, most blue and pink varieties will naturally change colour as they age and depending on the pH of their soil; flowers will tend to be blue in acidic soils, purple in slightly acid to neutral soils and pink in alkaline soils. Try mixing hydrangeas with hostas, heucheras, ferns and grasses, begonias or geraniums. Dried, they make fantastic decoration.
Plant in moist, well-drained, moderately fertile, humus rich soil in sun or partial shade. Keep in mind that young spring shoots are susceptible to frost damage.
Hydrangeas are supplied in 9 or 13 cm pots depending on the variety. Always unpack on arrival and store in a cool place until ready to plant.
Potential problems, pests and diseases:
- Aphids: these sap-eating insects can weaken plants and spread viruses. Whenever possible, pick off by hand using gloves.
- Capsid bugs: these sap-eating insects emit a toxic saliva that eventually causes the plant tissues to die. Leaves are peppered with small holes and often grow distorted. In some cases, flowers may not develop correctly and buds may fail. Dispose of any deceased plant material and debris in winter to prevent issues in spring and summer.
- Red spider mites: these tiny sap-eating mites cause leaves to become mottled with pale spots. In extreme cases, affected plants may shed leaves and potentially perish. Since red spider mites thrive in dry, hot weather, regularly spray foliage with water to discourage any attacks and keep an eye out for tiny mites, eggs and cobwebs. Dispose of any deceased plant material and debris before spring to prevent risks of infestation.
- Scale insects: these sap-eating insects may cause any seriously infected plant to loose vigour and prematurely shed leaves. Spot these pests early! Keep an eye out for any white egg formations from June onwards and watch out for wasps and ants! Hydrangea scales produce a form of honeydew that is attractive to them.
- Vine weevils: these black/grey beetles like to feed on ornamental foliage in spring and summer whilst larvae wreak havoc in autumn and winter by devouring plant roots. Host may wilt and potentially die. To prevent infestations, maintain good garden hygiene by disposing of any deceased plant material and debris. Additionally, take a moment to regularly inspect susceptible ornamental plants in spring and summer evenings — vine weevils come out at night — and pick off any visible pests using gloves.
- Botrytis/grey mould: this fungal disease usually caused by excessive moisture, warm temperatures and poor air circulation can initially be seen as brown spots/grey mould on the leaves and stems. If you spot any signs of this disease, immediately remove affected bulbs/plants and destroy. Botrytis is an airborne virus and can spread rapidly in the breeze so do not compost infected material.
- Honey fungus: this fungal disease attacks roots and may cause hosts to die. Watch out for thin layers of white fungus underneath the bark located near the base. Dig out and burn any infected plants including all of their roots at first sight.
- Leaf spots: these bacterial/fungal diseases can usually be seen as sooty growths or spots on the leaves — these will progressively turn brown with a yellow margin before eventually dying. Remove and dispose of any infected leaves.
- Powdery mildews: these fungal diseases usually caused by planting in the shade or by poor air circulation can be seen in the form of white, powdery coating on the leaves. Cut off any infected material before disinfecting your scissors.
- Viruses: viruses can cause a number of problems ranging from the appearance of deformed leaves and flowers to colour patterns and streaking. It is advisable to lift and destroy any affected plant at first sight.