Buddleja -- Butterfly Bush

One of the best parts of working here at Olbrich is interacting with the visitors when they come to see the gardens. We are forever getting quizzed about the plants which keeps us on our toes -- What is that? Is it easy to grow? Where can I get it? -- and usually in that order. It’s always easy to tell which are the keenest gardeners. They ask the toughest questions and usually are a bit skeptical of our answers -- probably withholding judgment until they grow the plant themselves.

Quite naturally, most of the questions are regarding plants that are in full bloom, and more times than not, plants that are a bit more unusual One plant that fits into this category and is one of our favorites here at Olbrich is butterflybush (Buddleja davidii) and its many cultivars. Although they don’t look like much at this time of year, come August you’ll wish you planted at least one.

This beauty is a hardy woody shrub in southern climates, but is known as a die-back shrub in the north, since it dies to the ground each winter. A die-back shrub needs to “do” two things: first it needs to be root hardy so that it actually resprouts each spring and second, it needs to flower on the current seasons growth since it’s starting from scratch each spring.

I’ll be the first to admit that butterflybush is not absolutely hardy and may die outright one in every 3 or 4 years, but it is still worth growing for its fantastic floral display. I’m sure we would plant it as an annual every spring if we had to. Don’t despair if it does happen to perish, since it is a quick grower and will always flower the first year of planting.

We mulch our plants at the Garden each fall to help insure there survival. First we mound the base with about 10-12” of soil and then put 3-4” of shredded bark mulch on top of that. This will get them through all but the worst of winters.

Butterflybushes are not fussy growers, needing full to half day sun -- the more sun you give them, the more flowers they will reward you with. A well-draining, fertile soil is best (isn’t it always?) but almost any soil will do. Give them plenty of fertilizer and water in the beginning of the growing season, since bigger plants will produce bigger flowers. 

Buddleja davidii grows 10-15' tall where it is fully hardy, but for us it generally reaches from 4-7,' depending upon which cultivar you are growing and how warm the summer is -- the hotter it is the taller they’ll grow. The form is vase-shaped and fairly open, with long upright to arching canes. We often pinch out all of the soft shoot tips on our plants when they are about 8-10" tall, which creates full well formed plants later. The leaves are lance shaped -- blue-green to medium green above with attractive white or silvery undersides. Unfortunately, fall color is non-existent and the leaves usually freeze on the plant and fall to the ground green or brown -- can’t have everything I guess.

The real attraction of growing this plant is its spectacular floral display from July until frost. Large, colorful, fragrant, cone-shaped panicles (similar to lilac, but bigger) of white, pink, blue, pale violet to purple and red-purple, often with an orange eye in the center of each individual floret. Some cultivars can produce huge panicles 3-4” wide and over 2’ long!

When butterflybush is covered with flowers in late summer its fragrance fills the air with the sweet scent of lilacs, hence its other common name, summer lilac. If the scent happens to lure you in, you’ll probably be greeted by a handful of monarch or swallowtail butterflies feeding on the sweet nectar.

There are over 25 cultivars of Buddleja davidii listed in horticultural references, most differing mainly in flower color and habit -- probably 10-12 of these are commonly available at local garden centers and nurseries. Every cultivar that I have seen produces fragrant flowers and is a butterfly magnet.

I’ll mention just a few of our favorite cultivars that we grow here at Olbrich. ‘Pink Delight’, as its name suggests, has large (12-15” long) clear pink flower panicles and reaches a height of about 6’ by the end of the growing season. We planted this cultivar in the mixed borders of the Sunken Garden where its flowers blend nicely with other cool-colored perennials.

‘White Profusion’ sports clean white 6-8” long flower panicles and grows to about 6’ tall.

‘Black Knight’ is clothed in rich, deep purple flowers and grows to around 6-7’ tall. It is reported to be somewhat hardier than other cultivars.

‘Dubonnet’ bears large 12-14” maroon-red flower panicles with light orange-throated florets. This cultivar also grows to about 6’ tall.

‘Harlequin’ is unique in that it produces cream variegated foliage. The leaves emerge yellow-edged then the yellow tones down to cream as the growth hardens off. The flowers are 6-8” long and reddish-purple in color.

Two of our favorite cultivars for container use are ‘Nanho Blue’ and ‘Nanho Purple’. Both are compact growers with thin stems and fine-textured silvery leaves. ‘Nanho Blue’ grows to about 3’ and produces 4-6” long light blue panicles. ‘Nanho Purple’ reaches around 4’ tall and its flowers are medium purple with orange eyes.

Whichever cultivar you choose to plant, try to site it near a path, patio or deck where you can enjoy the splendid fragrance -- I’m sure the butterflies will appreciate them as much as you will!