Buddleia really lives up to its famous reputation for attracting Butterflies. Each fragrant flower is filled with aromatic, sweet nectar that Butterflies and Bees adore. This distinctive perfume and flower’s shape contribute to its common name, “Summer Lilac”.
Buddleia officinalis definitely lives up to this reputation. This is a rather well-behaved open shrub 2-6ft/60cm-2m broad and tall but can get larger. It can flower anytime from Mid/Late Spring onward into Late Autumn with large irregular clusters of Lilac-coloured flowers on semi-evergreen shrubby plants that closely resemble the true Lilac (Syringa).
While the blooms can resemble Lilac, the most well-known like Buddleia davidii (Orange-Eyed Butterfly Bush) are generally somewhat conical, narrower and more symmetrical than the true Lilac, yet there is an obvious similarity and a remotely familiar fragrance. B. davidii and its many cultivars can grow anywhere from 1-3m/3-10ft broad and tall. It is often semi-trailing and features a variety of vivid colour shadings as well as pastels and white all with a distinctive orange eye and a lovely perfume.
Other Buddleia species have flowers shaped like globes or dramatic spear-like spikes. Flowers appear in many shades of nearly blue, mauve, lavender, lilac, pink, purple, and white in the South American species; gold, orange and yellow shades are common.
Most bloom in Late Spring through Autumn. But Buddleia. salvifolia (Sagewood) is Winter-Spring flowering and (semi) evergreen. True to its name, the leaves often have a silvery cast and somewhat woolly texture, especially underneath, similar to some Salvias and Sage. The flowers of B. Salvifolia possibly bear the most resemblance to true Lilac blooms, but usually in a cream shading or rather washed-out shade of pink; off-white, sometimes almost grey.
Occasionally a really fine cultivar will emerge with truly Lilac, lavender, mauve, or deep purple blooms and occasionally nearly blue flowers. But even in the washed-out varieties, their perfume makes up for this and Bees, Birds and Butterflies, especially the Monarch find, then an irresistible destination for nectar and will often roost in well established matures shrubs.
Because of their silvery grey-green leaves and often near-white blossoms, they are highly valuable in the grey/silver or white garden landscape theme. And being abundantly Winter/Spring-flowerings makes them even more valuable. They can even withstand mild frosts and freezing once established but need protection while young.
Buddleia salvifolia is a South African native species. Most other species come from tropical parts of China and India where they remain evergreen or partially so. An exception is B. globosa which is a Peruvian species with distinctively different, nearly round clusters of many small flowers in glowing yellow and orange shades. These appear throughout the warmer Summer months. A similar cousin from Mexico is B. cordata with more typical long, slender, sometimes branching clusters of cream, gold, orange or yellow flowers.
Many Buddleia have adapted to colder climates by becoming deciduous. Most can survive some significant freezing down to sheltered parts of botanical Zone 5-6 (temperatures as low as -20C) or warmer. Even when killed to the ground, they often re-emerge from their root stock, especially if this is protected with freeze-resistant mulch.
In the winterless semi-tropical climates Buddleias can grow into nearly evergreen large, open bushes to 3-5m/10-16.7ft and as wide. They are so hardy that they can sometime become invasive. In climates much to their liking, their seedlings can arise in almost any location including the cracks in brick and stone walls, between paving stones or out of gutters. Old canes are reduced to mature wood once flowering finishes or can be cut back much more severely without damage. Even when an old shrub is cut completely to the ground, it will often re-emerge as a much stronger new shrub the flowing Spring and Summer.
In some situations, Buddleias are also good shrubs to grow in the glasshouse for winter blooms. If it were not for their large and rambling habit of growth when subjected to lower light, they would make relatively easily-grown houseplants. Buddleias are very fast and easily established in any rich, light soil that drains freely. They flower well in large tubs and are hardy by the coast.
Autumn is an excellent time to plant Buddleia especially in mild climates. In freezing cold climates, Spring is best. But containerised Buddleia shrubs can be established almost any time from Spring through Autumn and even during Winter in milder climates. Buddleias are most easily moved as established shrubs later once they go (semi) dormant. Or also in early Spring in cold climates once danger of frost has passed.
In mild climates, simply cut back new growth and dig out as many roots as possible so that the remaining top growth and root ball nearly match. Half-ripe cuttings will strike quickly in peat; sand; seed-raising mix or a mix of these ingredients, especially if first dipped in hormone powder or solution. Or take more mature wood later in Autumn and start in a sand/peat mix under glass or with shelter or place in a sheltered cold frame.