Much of the diversity among scented pelargoniums happens by chance. Pollinating insects are natural, though inadvertent, hybridizers. They visit hundreds of flowers each day, and so the parentage of the seeds that result from their efforts is always unknown.
People have learned to duplicate the pollinating skills of insects but with a difference: they can choose the parent plants, intentionally creating a new kind of plant or improving the characteristics of an existing one. For instance, if you have a scented pelargonium with lovely blooms but an ungainly appearance, you might cross it with one that has nice, compact growth, hoping that the resulting hybrid will have both attractive form and flowers. Of course, plant breeding is seldom this simple. Though you might get lucky on the first try, it often takes hundreds of crosses and many years of work to achieve the desired results.
Hybridization is the production of offspring from parents of different genetic makeup. In plants, it is achieved by cross-pollination: the transfer of pollen from the anther of one plant to the stigma of another plant. The pollen germinates on the stigma and grows down the style into the ovary, where fertilization occurs and the seed develops. The plant that donates the pollen is called the pollen parent, and the one receiving the pollen is the seed parent. The offspring of such crosses are called hybrids.
More often than not, which characteristics the offspring will inherit are not easily predicted. Frensham is the first reported hybrid between P. citronellum (formerly known as Mabel Grey) and Prince of Orange; its leaves are less sharply lobed than those of P. citronellum, and it is shorter, but the flowers and scent are the same. Chocolate Mint is a cross between a Peppermint and Giant Oak. The leaf is shaped like the former but lacks its peppermint scent and fuzziness; “chocolate” refers to the attractive, brownish purple blotch in the center of each leaf, not to the scent, which is pungent.
Many varieties of scented pelargonium are so dissimilar genetically that they will not produce viable seeds when cross-pollinated. Discovering which ones will readily hybridize is often a matter of trial and error, however, so just have fun and give it a try. The optimal time to try your hand at hybridizing is in spring or early summer, when the greatest number and kind of scenteds are in bloom.
How To Hybridize:
1. Carefully select the parent plants. The stigma of a flower is receptive for only a few days or even hours; this time must coincide with the time that another plant is producing pollen. A 10¥ hand lens is helpful in gauging flower development: ripe pollen looks like flour, and a receptive stigma appears sticky. Avoid any flower that already has pollen grains on its stigma, but don’t worry if a flower’s pollen falls on its own stigma. In scented pelargoniums, pollen usually develops after the time that the stigma is receptive—nature’s way of discouraging self-pollination.
2. With tweezers, grasp a stamen of a flower of the pollen parent just below the anther. Carry it over to the seed parent, and brush its pollen onto all five arms of the stigma of a flower of the seed parent. You may need more than one stamen to supply enough pollen.
3. After pollinating the flower, cover it with a small, fine-mesh bag to keep out pollinating insects and windblown pollen. Small, drawstring muslin tea bags (available at health-food stores) or empty, unused paper tea bags work well. Secure the bottom of the bag with cotton string and tag the flower with an identification number. Careful record keeping is important for evaluating hybrids and in planning future crosses. Clean tweezers with alcohol before reusing.
4. If fertilization is successful, seeds will soon form. Remove the sack after a week or two, then gather the seeds when ripe and plant them.
5. Carefully evaluate the resulting seedlings. Grow the plants for a year or more and look objectively at their performance and appearance. If they seem like worthy garden plants, you can consult authorities, catalogs, and reference books to determine whether your hybrid is truly new, or write to the International Geranium Society, PO Box 92734, Pasadena, CA 91109-2734. All further propagation of your hybrid should be done vegetatively to maintain its genetic makeup.
With his wife, Dotti, Jim Becker is co-owner of Goodwin Creek Gardens in Williams, Oregon, and coauthor of An Everlasting Garden (Interweave Press, 1994). He has been writing articles for The Herb Companion since 1989. Faye Brawner is a geranium collector and hybridizer and owner of Faye Brawner Geraniums, a nursery in Buckhannon, West Virginia. This article is adapted from Scented Geraniums, an Interweave Press book scheduled for release in May.
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Growing Scented Pelargoniums in Containers