In the Garden:
Northern California Coastal & Inland Valleys
If fragrance is what you crave, you can't do better than lilies.
Fragrance in Plants
Lately I've been thinking about the importance of fragrant plants in the garden. Certainly colorful annuals brighten the world around us, and trees and shrubs provide shade us and contribute to the very air we breathe. But what is the purpose of fragrance, other than to entice insects and induce pollination?
How Fragrance Works
The fragrance of plants originates in a metabolic process when essential oils combine with naturally occurring alcohol and acid. These combinations of chemicals are called esters. The ester molecules are heavier than air, which is probably the reason birds have no sense of smell while dogs and other ground-dwellers have acute olfactory senses. Thank goodness sweet peas produce their abundance of flowers right at nose level.
Fragrance in Hybrids
Many hybrid varieties have had the fragrance bred out of them. The delicate fragrance of heliotrope, for example, is nothing compared to what it was in the past. The plants are stronger and produce more flowers, but the loss of fragrance is the ultimate cost. The hybrid tea rose is another example. The perfectly formed flowers and disease-resistant plants are stellar, but the fragrance is just not there anymore. Some hybridizers are working on the fragrance factor. Star Roses, for example, has been developing hybrid teas that you can enjoy with your nose. Their 'Queen Mary II' hybrid tea has combined the heady rose scent with a base note of banana.
Some flowers produce their fragrance at night to attract moths as pollinators. Nicotiana is an example of a flower that has no scent at all during the day, but stick your nose in one after the sun goes down and you are captivated, just like a moth!
Some fragrant flowers bloom in winter. Sweet olive (osmanthus), Daphne odora, hyacinth, and yellow primrose (Primula polyanthus) are examples of winter-blooming fragrant plants. I don't know why only the yellow flowers of the primrose are fragrant while the pinks, blues, and oranges have no scent whatsoever. Since most flying insects have not yet hatched for the season, winter-flowering plants are usually pollinated by birds searching for berries and seeds, but ants and other ground-dwelling insects play their part.
One of my favorite floral fragrances is that of the Magnolia grandiflora. The creamy white blossoms have an intriguing citrus scent that carries on the cool morning breeze. Stick your nose in one and see if you don't fall in love. Another favorite of mine isn't a flower at all, but a shrub called Breath of Heaven (Coleonema). The foliage has a clean, refreshing scent that is released when the plant is disturbed. Plant Coleonema along a walkway where you can snip a twig to carry with you.
We all look forward to the scent of lilacs in the spring. Lilacs generally do better in areas that have a real winter, but for some reason the sandy, slightly alkaline soil and cool summers of south San Francisco are ideal and lilacs bloom profusely there. If you smell flowers in South City, you can bet lilacs are nearby.
If fragrance is what you crave, there is no better source than the lily. Plant lily bulbs, the Asiatic and Oriental hybrids in particular, in fast-draining soil or in containers. I love lilies and try to keep them in my little garden downstairs, although I have never seen them fully in bloom because the patrons of the neighborhood bar beat me to them. Oh well, I guess everybody likes to stop and smell the flowers once in a while.
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