He doesn’t include many herbs, but using his methods as a guideline, I’ve worked out treatments for the herb seeds I wanted to germinate. Deno’s great contribution has been to pinpoint the optimum conditioning regimen for the seeds of some 2,500 species of plants. Methods of treating seeds to overcome delay mechanisms, called conditioning, have been known for some time in a general way but had not been worked out in detail for many species. The seeds of desert plants germinate only at cool temperatures, a survival mechanism that ensures that the seedlings will have the benefit of some moisture before scorching temperatures set in. Many kinds of seed have a temperature requirement. In other kinds of plants, the barrier is physical, such as a hard seed coat through which water cannot penetrate to initiate germination. Germination of seeds encased in fleshy fruits generally is prevented by chemical inhibitors in the pulp that diffuse into the seed. After a season of drying, however, the seeds gradually begin to lose their viability, although some kinds will remain good for years. The seeds of many familiar garden annuals and vegetables require a period of dry storage, typically from one growing season to another, to destroy germination inhibitors within them. Seeds of every plant species are chemically or metabolically alive, although vegetatively “on hold”: Each contains one or more mechanisms to prevent germination until after it has been dispersed from the mother plant and conditions are favorable for its survival. Among these are ‘Lady’ lavender (also faster growing than the species), various salvias, monardas, and others on the chart in this article’s image gallery. Seed strains are selections that come true from seed. To obtain lush plants the first season from such slow growers as rosemary and lavender, buying established plants is a necessity.Ĭultivars (cultivated varieties) of rosemary, lavender (except ‘Lady’), thymes, mints, artemisias, santolinas, some salvias, and origanums also must be propagated by means other than seed (such as cuttings) to ensure that their offspring resemble the parents in every way, as must French tarragon, which doesn’t produce viable seeds. Some gardeners enjoy discovering these differences, but if you’re looking for consistency, grow the species from cuttings or roots or purchase established plants–don’t bother with seed. When grown from seed, rosemary, lavender, thyme, and mint species show variations in leaf, flower color, habit, even flavor. Until Deno’s extensive germination trials, the requirements of many of these species were little known. Although this is true for about 50 percent of plants from temperate regions, including the most important food crops and common garden flowers, the other 50 percent, as well as exotics of all types, desert and alpine plants, and wildflowers, require different treatment if germination is to take place. Deno, a retired chemistry professor, challenged the old notion that seeds need only warmth and a little moisture to germinate.
Deno’s pathbreaking book Seed Germination, Theory and Practice, first published in 1991, provided a new approach. Too often, the seeds vanished in the soil without a trace, and I didn’t know why. In the beginning, however, I had little success with growing herbs from seed. I thrill to the initiation of growth and to witnessing the first stirrings of life in seeds I have planted by my own hand–a certain perkiness, a swelling and break in the seed coat, then the tiny leaves unfolding and springing toward the light.
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