Tradescantia (also known by the common name spiderwort) is one of the foundation plants in my garden. By this I mean that I grow a number of different varieties of this plant and I grow them in many different parts of the garden.
The tradescantias in my garden are hybrids of the native North American Tradescantia virginiana. They have thick stems with grass-like foliage and grow dense clusters of flower buds at the end of each stem. The flowers are about 1” wide, with three petals, feathery stamens and bright yellow anthers. Each flower opens for only one day, but there are so many buds on each stem, that flowering can last for many weeks. The flowers also close in the heat of the day, so this plant is most appropriate where it will be enjoyed in the morning. When I bought my plants, they were labeled as Tradescantia x andersoniana; but apparently this hybrid name is invalid — according to the Floridata website, because the proposers never completed the necessary paperwork. Floridata and others now refer to these hybrids, which combine T. virginiana with two other North American natives, T. ohiensis and T. subaspera, as the “Andersoniana group.”
Reference works usually describe tradescantia plants as flowering in spring and early summer and then going dormant, although they can be cut back and they will flower again in fall. The descriptions usually also say that the flowers close up “by mid-day.” Because both of these characteristics seem to be responses to heat, it is not surprising that the plants behave somewhat differently in my cool Maine garden. My tradescantias usually begin blooming in mid-late May; and although they may slow down some in late summer, they often bloom continuously until frost. Similarly, in my garden, the flowers often stay open until mid-afternoon; and on cool, overcast days or in the cool fall air, they may not close up at all. I’ve also found descriptions of tradescantia as needing very moist conditions or part shade not to be true in my cool climate; they thrive in my sandy soil, attaining heights of 2 1/2’ – 3’, and they grow happily in full sun as well as in part shade.
Tradescantia form large clumps quite quickly, so they are great plants for a mature look by the second season in the garden. I do find that the larger clumps tend to flop over, particularly after heavy rain, so I use peony hoops to support them. Tradescantia also tend to self-sow; I don’t regard this as a big problem in my garden, and I am always excited to find out what my new volunteer flowers will look like. Most of my volunteers are in the blue-violet-purple range, but I also have seedlings of the lovely white and blue ‘Osprey.’
Tradescantia seem to be more often associated with the south, where they are particularly likely to grow as wildflowers. But I think they are wonderful plants for cool-climate gardens. The hybrid varieties are rated as cold hardy to USDA zone 3, and the length of both the bloom day and the bloom season are likely to be extended in more northern gardens. I love these plants, and I wouldn’t be without them.