The science of seed morphology—how plants reproduce sexually and make seeds—isn't magical or miraculous. And while plant reproduction relies on complex biophysical and chemical elements, simple techniques are still important to the process. More than 200,000 green plants in our gardens begin life with the classic progenitors—the sperm and the egg.
Sniff a deeply scented oriental lily and you'll likely come away with a yellow-to-orange smudge of pollen on your nose (but if it's on your collar, the stain won't wash out). Grains of pollen contain male plant sperm, determined little bundles of DNA in search of an egg waiting in an ovary. Some plants, such as holly and squash, produce flowers that are either male or female. The males manufacture pollen on their anthers to fertilize eggs in the ovaries of female plants. Bees and other pollinating insects carry the pollen on their furry jackets to the prominent female stigmas atop long, tube-like pistils, leading the sperm to ovaries at the base of the flower. Insect pollinators are essential to the production of most fruits and vegetables we eat. Wind pollinates some plants such as corn and grains; you can pollinate squash plants yourself with a small brush, collecting pollen from the male (straight stem beneath the flower) and brushing it on the sticky stigma of the female (rounded ovary under the blossom). Other plants such as amaryllis and tomatoes have perfect flowers, with several male anthers and a single female stigma in each blossom, requiring only wind or a squirming bee to move the pollen about. If your garden is windless or short on bee action, gently flicking or ruffling tomato blossoms with your hand will scatter the pollen and help to set fruit.
Successful pollination results in seed production, satisfying the plant's effort to perpetuate its species. The plant ceases making flower buds to ensure all its carbohydrate energy goes toward maturing seed embryos, hardening the seed coats and reducing moisture in the internal tissue of the seed (the endosperm) to below 10 per cent; too much moisture in seed tissues encourages fungus that can kill the embryo. Plants can be kept blooming longer if they are deadheaded each week, removing the spent blossoms before seed-making hormones shut down flowering.
Species plants have the strongest seed-making potential. Fancy cultivars or double flowers with extra petals often have weakened reproductive abilities. Many hybrids are sterile hermaphrodites (neither male nor female), such as the ‘Orange Marmalade' martagon lily, incapable of making pollen or seeds. New methods are being used to produce plants quickly to meet market demands. Tissue culture and meristem (or growing tip) division are forms of laboratory plant cloning that bypass sexual reproduction and the time needed to make seeds. But to me, the humble bumblebee is still the friendliest and most reliable method of reproduction.