Buddleja davidii

Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Asterids
Order: Lamiales
Family: Buddlejaceae
Genus: Buddleja
Species: B. davidii
Binomial name
Buddleja davidii

More commonly known as the Butterfly this is considered a weed by some people. You'll find it growing in wall crevices I've even seen it growing on the gable end of a building.

However it attracts Butterflies which is an amazing asset to any garden.

They are vigorous growing shrubs with long arching stem that will reach 3-4m in height and near 2m across. It flowers July to august and produces amazing panicles of flowers ranging in colour from deep purple through reddish purple to lavender and white.

This is the most commonly occuring variety but there are several other's well worth looking at,
1) Buddleja Globosa - Orange ball like blossoms
2) Buddleja alternifolia - Pale Purple
3) Buddleja Royal Red - Reddish Purple

Buddleja will grow in most soil types (including chalk) but prefer a deep loam and a warm sunny position.
B. Alternifolia prefers a dry site

Planting them is best done in autumn time well before 1st frost's appear.

Pruning best way to control the vigorous growth is to prune early feb to within a 5cm or so of the old wood. Being as vigorous in growth they will quickly make new growth.

B. globosa requires little or no pruning but will 4-5m in height.