Euphorbia obesa - Collecting Seed
If you have a male and female plant ofEuphorbia obesa in flower at the same time there's a good chance the flowers on your female plant will be pollinated and set fruit. The fruit is a small rounded capsule holding three seeds. A modest sized plant, such as the one at the right, usually produces six to ten fruits and thus 18 to 30 seeds. However, there's a difference between the female producing seeds and your chances of harvesting them.
As the fruit of E. obesa dries, pressure builds up along the seams, and when one of these seams splits, the seed is propelled outward with substantial force. The force is great enough to propel the seed up to ten feet (3 meters) away from the plant. If you do not have some type of mechanism in place to collect the flying seeds, or prevent them from being propelled, you will lose most, if not all of the seeds.
The plant at the right has propelled most of its seed. There is only one fruit with seed remaining. There are a number of tricks use to prevent the fruit from splitting and throwing off the seed. One is to put a dab of glue on the side of the fruit. This will prevent the fruit from splitting with force and hold the seed in a partially split fruit or allow the seed to drop into the pot. A piece of tape is sometimes used around the fruit to accomplish the same thing.
Another method of getting the seed, is to collect it after it has been expelled from the fruit. Some growers cover the top of the plant with a piece of mesh or nylon, (like a hat covering the fruit) to trap the seed when it is propelled. The catching material is secured around the plant with a rubber band or string. I have a number of plant and I prefer to use a large trap (seen at right). I use a plastic crate that is lined inside with window screen. The plants with fruit are placed inside and the crate covered with another piece of screening. As the seeds are propelled from the fruits, they are trapped within the screened crate. Some seed will fall into the pots but 80 percent usually ends up on the bottom of the screened crate. I can collect hundreds of seeds with this method with very little work on my part, save making the trap crate. The screen allows air and light (although there is about a 20 light reduction due to the screen) to get to the plants and I keep the plants dry during this seed collection period.
Of course you still need the basics, flowering females plants to produce the fruit and seed, and at least one male plant in flower at the same time for pollination. I have never had to take a hand in the pollination. My plants are outside and ants seem to do most, if not all, of the pollinating. Strangely however, I have also had flowering plants set fruit inside the house, and I never saw a single ant. I have no explanation for how this pollination occurred....invisible ants....or poor grower eyesight.