On Gardening: Christmas Senna a glorious gift of the season

October 27, 2014

The Christmasbush senna is an attractive asset to the fall butterfly garden.

Just about the time you least expect it the Christmasbush erupts into a yellow explosion of bloom with such staggering beauty it stuns all who see it. After all this is a color in the spring or summer and surely not expected from mid-October through November and December.

But such is the case for this large shrub known botanically as Senna bicapsularis. In addition to the official Christmasbush it also goes by names such as winter cassia, butterfly cassia and Christmas senna. In our area the bloom period lasts 6 to 8 weeks or until a frost causes its retreat. It is considered a zone 9-10 plant and a zone 8 perennial. At the Coastal Georgia Botanical Gardens in Savannah ours was simply stunning through December and then the 30-year freeze hit in January. If I lived in zone 7 and had access to seeds, I would try it on the protected side of my home or try it as an annual.

As was expected it did die to the ground but has rebounded robustly and is pushing 8 feet in height. It is native to South America and has escaped in southern Florida and some parts of the Caribbean causing it to get established in disturbed areas. In areas with frost it will be held in check.

If you have ever wondered what plants host the sulphur butterflies, this is one of the best. They will feed the orange-barred sulphur, the sleepy sulphur and the cloudless sulphur. In our garden during this time we typically have an abundance of sulphurs that seem to be getting nectar from every plant with a bloom.

Christmasbush senna will tolerate partial shade, but it is a fertile bed in full sun where it reaches it true potential. It should go without saying, but please apply a good layer of mulch after planting. Itís not a high-maintenance plant at all. A couple of times during the growing season pinch or prune a little to develop a bushy mound. In our gardens we are growing it adjacent to one of our historical pillars in the Mediterranean Garden.

In its glorious bloom of shocking yellow it will be in close proximity to the ultimate companions of Purple on Purple Mexican Bush sage. In other areas of the garden they are growing in beds geared toward butterflies and hummingbirds. Here they tower over Mystic Spires Blue salvia, Blue Fortune agastache, bog sage and a layer of Red-spread lantana.

Slender brown pods reaching 4 to 6 inches long usually follow bloom, allowing equally opportunity for everyone to have their own propagation material. The seed coats are hard and can be lightly scratched or scarified with sandpaper, so that water can penetrate for germination. Some suggest pouring boiling water over seeds that have been placed in a tea strainer.

Christmas senna is still not a staple at every garden center, but we have been fortunate and found them rather easily. You can also count on finding some great Internet sources. If your neighbor has Christmas senna, you should be in luck. Once you get yours youíll be celebrating this time next year.



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