Mark Dimmitt is widely known for his success with tillandsia seed culture and interesting hybrids. His experience with tillandsias is summarized in new discussions of basic culture, artificial pollination, selection of plant parents, and an analysis of results. We propose this material as an elaboration of Cultural Handbook chapters on seed culture and hybridization. We invite your comments. -TUL]
The genus Tillandsia has an undeserved reputation for being difficult to grow from seed. In fact, tillandsias are among the easiest plants in the world to grow. Most species also have a reputation for being very slow. Some are, but under generous cultural conditions many of the popular species can be grown to maturity in five years or less. This article describes tillandsia propagation from sowing of seed to maturity.
Sow Tillandsia seed as soon as possible; it remains viable for only a few weeks under normal environmental conditions. It may be possible to freeze extra seed but I have not yet tried this experiment. Refrigerated seed keeps for at least a few months.
The seeds of atmospheric tillandsias need moisture, light, and good air circulation for germination and survival. A substrate which tends to remain soggy will develop a growth of algae which will suffocate the seed or seedlings. The same problem develops if the air is too humid and stagnant. I sow seeds on plastic window screen in open-mesh flats suspended in the air. Nylon stockings stretched over a wire frame also work well, as will chunks of tree fern fiber. Any airy substrate that will not decay for at least three years or so seems to be satisfactory.
Spread the seeds thinly on the substrate so that you can see individual seeds instead of clumps. The more widely spaced they are, the longer it will be before they become crowded and require separation to prevent stunting. Larger seedlings are also much easier to handle without being damaged.
The most serious problem during the tiny seedling stage is suffocation by algae. The presence of algae indicates too much water, it can be alleviated by one or more of the following actions: reduce watering frequency, lower humidity, increase light, or increase air circulation. If algae has run rampant by the time you discover it, its hygroscopic nature keeps the mass soggy, and requires positive action. If the plants are large enough to handle, move them to a clean substrate in a drier location. If the plants have been covered with the goo, try an algicide such as Physan or Fore combined with a move to a drier location. Avoid copper compounds; they kill algae very well, but it is easy to poison the tillandsias too.
Unfortunately, copper-free algicides do not work very well. They frequently damage seedlings also. Prevention is the best practice.
When they are at least ½ inch in size, they are ready to separate into individual plants. Many species and hybrids have strong roots as small seedlings, making separation somewhat tricky. If you pull on the tops of the plants, you are likely to rip their hearts out. It is necessary to tease the clumps apart carefully until you can get your fingers between the plants, then to work the roots apart without crushing the fragile meristem near the base of the rosette. If the seeds were sown sparsely, this is less of a problem, although some species will root firmly to the substrate and cause the same difficulty. The larger the seedlings the easier they are to handle without damage.
In a few species, seedlings multiply into clumps of rosettes at a very early age; Tillandsia ionantba and T xiphioides often do this. In such cases, do not try to separate them; just let them cluster, at least until they can be easily separated.
Once separated, it takes the least time (but more greenhouse room) to space the plants so that they can reach flowering size without being moved again. This ranges from 1-2 inches for T stricta or T ixioides, to 8 inches for T streptophylla or T duratii. It is easier said than done. Each square foot of T stricta seed sown, for example, will expand to 12 square feet of mature plants if you save all the plants. Lack of space quickly creates a crisis!
As the plants shift into the faster growth phase and approach maturity, they need more light to develop their best form. I have four to five layers of benches in my tillandsia house. I grow young seedlings on the bottom two or three layers, larger seedlings and soft or green-leafed species on the second layer, and mature plants of the hard and gray-leafed species on the top layer.
[Dr. Dimmitt is curator of plants, Arizona-Sonora Desert Museum, 2021 N. Kinney Rd., Tucson, Arizona 85743.]
Tillandsia gerdae at 4 years!!
On a Paroz biscuit.
Tillandsia retorta at 2 years!
On natural cork.