Sowing Seeds

Seed Germination: Taking it to the next level

Anyone who has begun to take an interest in gardening inevitably ends up trying to start seedlings. We start with tomatoes and peppers, which are quite easy to grow, then we try our luck with increasingly difficult plants. There comes a time when the plants we are trying to germinate are unique, rare or have special requirements. For these advanced levels, there is a resource: Norman C. Deno’s Seed Germination: Theory and Practice.

Finding good information about seed germination is not always easy. You have to know where to look! Image: Layout by Mathilde Bourgeois on Canva.

What’s That Weird Old Thing?

First published in 1993 as a notebook of around 240 pages, this book became a must-have for anyone wishing to germinate plants that are a little more difficult to succeed. It is a vast directory of approximately 2,500 plants from 145 different botanical families. For each, Mr. Deno gives THE recipe! What temperature? For how long? What is the germination rate? What is the germination time?

Several years ago, the United States Department of Agriculture saw fit to make this document available to everyone, by putting it online . They literally digitized the original document! Nevertheless, since the plants are classified in alphabetical order by genus (the directory begins on page 82). The first pages of the book are worth reading and re-reading, as they thoroughly cover all aspects of seed germination: germination rates, germination inhibitors, mechanical treatments, storage, etc. This is valuable information that is almost never found in books about sowing, which are generally geared towards beginners.

Who’s This Norman Guy?

The author of this little gem, Norman C. Deno is a chemist and professor emeritus at Penn State University. Although he has published over 150 papers in the field of chemistry, he is best known for his important work on seed germination. He focused primarily on finding ways to remove germination inhibitors, which chemically and mechanically prevent a seed from germinating. Many seed companies, including Thompson & Morgan, have required his services and use his recommendations on their seed packets. Surprisingly, he was the one who invented the germination test technique, called the “baggie and paper towel”, later called the Deno Method ! It’s simply a sheet of damp paper towel, folded in half and placed in a plastic sandwich bag. The seeds are simply placed between the two layers of paper towel.

The Deno Method: Seeds inserted between two layers of paper towel. Image: Pixabay.

How to Decode it?

Once past the pages of the introduction, we arrive at the real directory and there, everything seems to be written in a foreign language! For example, for cranesbill (Geranium sanguineum), it is written “best in 70 D( 77% in 6–12w)”. This means that the best germination is obtained at a temperature of 70 F (21°C) in darkness (D for “dark”). The germination rate will be 77% and the seeds will germinate after 6 to 12 weeks (w for week). So, you have to be very patient! Twelve weeks is 3 months!

Here are the different codes used and their explanation:

Ttemperature (in Fahrenheit)
DSdry storage
WCwashing and cleaning
GA-3Gibberellin Treatment

In short, as soon as interest turns to seedlings of perennials, trees, tropical plants or alpine plants, Seed Germination: Theory and Practice becomes an essential work. It is thanks to this book that I have succeeded in many reputedly difficult seedlings, such as martagon lilies (Lilium martagon), Canadian rhododendrons (Rhododendron canadense) and many primroses (Primula spp.).

My very own paper version, ordered by mail, with a letter and stamps and everything. It has served me well (and still does). Image: Julie Boudreau.

Advanced sowers can also turn to another very good resource, Tom Clothier ‘s seed germination database .

Julie Boudreau is a horticulturist who trained at the Institut de technologie agroalimentaire in Saint-Hyacinthe, Québec. She’s been working with plants for more than 25 years. She has published many gardening books and hosted various radio and television shows. She now teaches horticulture at the Centre de formation horticole of Laval. A great gardening enthusiast, she’s devoted to promoting gardening, garden design, botany and ecology in every form. Born a fan of organic gardening, she’s curious and cultivates a passion for all that can be eaten. Julie Boudreau is “epicurious” and also fascinated by Latin names.

4 comments on “Seed Germination: Taking it to the next level

  1. Patrick Ryan

    Julie, I hadn’t heard of these sources. Thank you for sharing!

  2. “Norman C. Deno is a chemist and professor emeritus” Was. He died in 2017. But what a great legacy to leave behind.

  3. I thank you Julie for your valuable information and saving me wasting so much time on the onerous task of online research (which is mostly MIS-information)!

  4. Jt Michaels

    Thanks, Ms. Boudreau. I’ll be saving this one!

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