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.

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.

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:

germ.	germinates
d	day
w	week
m	month
y	year
T	temperature (in Fahrenheit)
DS	dry storage
WC	washing and cleaning
L	light
D	dark
GA-3	Gibberellin 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.).

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