The Gardeners Almanac

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Common name: Blue Spirea

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Week Numbers




Planting out


Semi hardwood cuttings


Blue double flowers

Caryopteris - Dark Knight

Caryopteris is a half hardy to hardy deciduous shrub that grows to around 1.2m (4ft) high with a similar spread.

The grey green leaves are aromatic, and clusters of blue bell like flowers appear from August to September.

In colder areas of the UK, plant out against a house wall to offer some protection.

Week 13:

Pot up rooted cuttings into 70mm (3") pots of potting compost.

Grow them on in a cold frame until planting out time.

Week 14:

Cut out previous year’s growth hard back to young healthy buds.

Weak or damaged stems should be cut out to ground level.

Week 32:

Take semi hardwood cuttings and place them in a cold frame to root.

Week 38:

Plant out any time from now until March in a sunny spot with well drained soil.

In exposed conditions it may require some form of protection during the winter months, against a south facing wall or fence would be ideal.