Chenille plants that go to seed
Greenhouse growers may wonder why sometimes chenille plants flower, but then go to seed, while others continue to flower.
I recently received a call from a greenhouse operator growing chenille (Acalypha hispida) baskets who was curious to know why all the baskets that had cuttings from one source were a bit smaller, and upon flowering, the plants were then going to seed. If you rolled the flowers in your hand, seed would fall out from the spent blooms. The plants grown from cuttings supplied by another source were growing normally and continued to flower without any hint of seed formation, and the inflorescences were also larger. As you can see in the picture, the smaller plant on the left was seeding while the larger plant on the right was not.
After studying the problem, I learned that chenille is a dioecious type of plant. According to Michigan State University Extension floriculture specialist Erik Runkle, “Chenille plants are dioecious, which means plants have either male or female flowers, not both.” When referring to the picture of the two plants, Runkle commented, “The plant on the left is female; the flowers were pollinated and thus have set seed. The plant on the right is full of male flowers and so will continue to flower whereas the females will not.”
Since these plants are propagated by cuttings, it is apparent that someone took cuttings from a female plant and not a male plant, thus the female cuttings will produce the smaller female flowers. Once pollinated, they will then produce seed while the cuttings from the male-only plants will produce the larger male flowers, not set seed, and continue to flower. This is pretty simple for the propagator to figure out; they will have to let the stock plants flower and then cull the female plants.
Most plants produce flowers with both male and female parts, and these are referred to as monoecious plants. There are a few other ornamental plants with dioecious flowers, but another example is holly (Ilex). In the landscape, mostly female plants should be planted to produce the attractive red berries (the male plants don’t fruit). However, there needs to be at least one male plant to pollinate the female flowers that then produce the red berries. Without pollination, the female plants won’t fruit and none of the plants will produce the showy red berries.