How to Grow Fragrant Butterfly Bush

Buddleja or butterfly bush is one of the most fragrant of garden plants (and indeed seeing it full of butterflies is a great gardening experience).
This Chinese native is hardy into USDA zone 5 (4 with deep mulch) but dies to the ground in this zone. It does perform much better in warmer gardens than this as it has demonstrated a tendency to self-sow and become a nuisance-invasive plant.
In these warmer areas of zone 7, butterfly bush can become a large shrub between 5-10 feet tall. In colder zones, it is not unusual to see it grow 5 feet in a single year before blossoming before being killed to the ground by winter.

Buddleja has a straggly growth habit – and those in warm climates who have an ugly looking plant can simply cut it to the ground to renovate it. The plant blooms on new wood so a heavy pruning will not reduce the number of blooms. It is a good thing those flowers are extremely fragrant as otherwise, butterfly bush wouldn’t be included in a good garden. It has no fall coloring to speak of although the leaves stay on the plant for a long time into the fall.
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But the flowers!

But the flowers! They range in length from 4-10 inches and while the most common color is lilac-purple, there are others in the pinks, reds, whites and shades of purplish-violet.
And these flowers are extremely fragrant while blooming from late summer to heavy frost.
Deadhead regularly to increase the number of blooms.
The seeds are carried in small fruit which has no ornamental value (too tiny).
Butterfly bush grows best in full sun and fertile soils. You’ll get the heaviest bloom there and shade will simply reduce the growth and flowers. I put a plant into the medium shade one summer to trial it there and it languished all summer throwing spindly shoots.

If you want to make a statement in the summer garden, plant buddleia in clumps. One plant alone can be quite ugly unless it is in bloom but a clump of three starts to look like a spreading shrub. One solution is to treat butterfly bush as an herbaceous perennial (I do) in the middle to back of the border and cut it to the ground in the fall along with the rest of the plants.
The seed starts readily and easily with a soil temperature of 70F and a small plant started in January will give a small bloom the first year in the fall (if grown in fertile soils). Named plants can be easily started using regular tender tip cuttings. Once the cuttings have rooted, transplant into larger pots and do not overwater; they have a tendency to rot quickly if overwatered.

Commonly available varieties include:

• Var. nanhoensis – Compact form (4′-8′ tall). Hybrids include
  ‘Nanho Alba’, ‘Nanho Blue’ and ‘Nanho Purple’, ‘Black Knight’ has dark
  purple flowers, and is slightly more cold hardy than the species.
• ‘Dartmoor’ – branched flowers with magenta/purple blooms. Can be a big plant.
• ‘Empire Blue’ – Flowers violet-blue with an orange eye. Upright growth.
• ‘Fascination’ – Lilac-pink flowers on large panicles 13″ to 18″ long. Vigorous
• ‘Harlequin’ – White and green variegated foliage with reddish purple flowers. Not a strong grower.
• ‘Honeycomb’ – An extremely popular yellow-flowering hybrid butterfly bush
• ‘Lochinch’ – A silvery leaf compact plant. The flowers are
  lavender with an orange eye and are in smaller clusters (5″-6″ long)
  than normal.
• ‘Royal Red’ – The best red-flowered form. Flowers up to 20″ long.
• ‘White Profusion’ – White flowers, but flowers only 6″ to 8″ long.