The image above shows my preferred technique for propagating plants from cuttings. I use small plastic cups that are 2 inches (5 centimeters) wide across the top. After inserting the cutting in the soil, I loosely wrap it up with plastic to maintain high humidity and the cuttings are placed in a frosted east-facing window. This provides bright light, which stimulates the cuttings to root more readily, while avoiding excessive sunlight that would scorch or bake the cuttings. Except for woody, hard-to-root cuttings, I do not use any rooting hormones.
Once the cuttings are well rooted, I'll harden them off by removing the plastic wrap and slowly acclimating them to full sun. Then I'll move them into bigger pots (unlikely) or plant them directly in the ground (much more likely). I prefer to place small cuttings like these into the ground for three reasons. First, the small pots, with their equally small quantities of soil, use up far less resources than larger pots. Second, they are much more easily handled than larger pots and create far less of a disturbance in the garden than does the planting of a larger plant. Lastly, small young plants adjust better to life in my sandy South Florida soils than do large plants. Often, large plants originally flourish but eventually perish when their roots, accustomed to living in a large pot of rich, organic potting soil, fail to adjust to growing in Florida sand. I also like this system because both the plastic pots and the plastic wrap can be reused indefinitely.
For curious readers, the plants above are, from left to right: Plectranthus parviflorus 'Sapphire Dream', which is being rooted in water; two cuttings of Calamintha coccinea (synonym: Clinopodium coccineum); and two cuttings of Piloblephis rigida 'Juniper'. All three are members of the mint family (Lamiaceae). The Plectranthus is a variegated cultivar of a plant originally native to South Africa and Swaziland. The Calamintha is native to Alabama, Florida, Georgia, and Mississippi. The Piloblephis is native to peninsular Florida and the Bahamas. Piloblephis rigida 'Juniper' is a cultivar originating from plants growing wild in Palm Beach County that has a very dense and crawling growth habit with mature plants forming a solid groundcover only a few inches high and resembling a prostrate juniper.
Image and text © 2012 Rufino Osorio