His details about what works for particular types and what doesn't have saved the rest of us much time and frustration. His books are now in the public domain, for those of you who would like to look them up. I did have to purchase my own copies way back when, but can testify that they were worth every penny!
He includes a lot of 40-70 or 70-40 recommendations, meaning that you need to keep the seeds at 40 degrees Fahrenheit for three months, before moving them to 70 degrees Fahrenheit--or vice versa. Lenten rose (Helleborus orientalis), for example, requires a warm period first, and actually begins germinating during its cold period. More often, however, perennials sprout after being moved from cold to warm conditions.
Because this can take so long, I often try to purchase seeds--or swap for them--in late autumn. That way they can go through their pretreatment in time to sprout in the late winter or early spring. You can see a hellebore seed that is just beginning to break open in one of my photos. The Helleborus Black Beauty, Dicentra exima 'Snowdrift', and unidentified Astrantia major type pictured here were all started from seed with the paper towel method.
Deno actually learned that method from a rock garden enthusiast named Margery Edgren, though he probably made his own refinements to it. He recommends certain brand name products as being the best for seed starting, but I'll just pass along his suggestions in a more generic fashion. They include "high wet strength paper towels" and "polyethylene bags," as well as "extra fine point permanent markers" to label the towels. I must admit that I don't always follow these instructions exactly, and have been known to use whatever paper towels and indelible markers are handy! I've found, however, that--as he warns--the softer paper towels fall apart faster. They also tend to coat rough seeds with damp lint, which can often be mistaken for white mold. I do try to stick to the thin polyethylene sandwich bags he specifies--the ones that use twist ties--as they admit more oxygen than the zipper varieties.
Some people suggest replacing the paper towels with coffee filters, as roots from the seeds won't be as likely to stick to them. They would probably solve the lint problem as well!
I fold a paper towel over on itself several times to form a "greeting card" shape, and write the name of the seeds and the date on the front. I then soak the towel in water and squeeze out the excess. I make my water 10% peroxide in an attempt to prevent mold.
Once the towel is damp but not soggy, I place my seeds on the inside of the "card" and slip it into one of those bags mentioned earlier. Then I fold the open end of the bag under and either stash it in a box in the refrigerator or on a high warm shelf, depending on whether the seeds inside require a 70-degree period before their 40-degree period. You can actually fit several of the paper towels inside the same bag.
I've found that paper towels in the refrigerator usually don't mold as much as those experiencing warm conditions. When mold does occur, however, it can be difficult to sort out what is only surface mold and what constitutes a real problem. Try prodding the seeds with a pencil eraser, and remove any that feel soft, as those are probably rotting.
The paper towel method doesn't work well for extremely tiny seeds, most of which require light for germination anyway. You will probably have to stick to traditional methods for starting those. It also isn't necessary for seeds that germinate quickly.
There are a few that require a wider range of temperatures, and are best started outdoors. You can use paper towels for that too, but will have to place them inside some type of weather proof--and rodent proof--container.
Be sure to check your towels once a week for sprouting seeds--perhaps more often, if you've just moved them from cool temperatures to warm. You will need to have some seed-starting mix handy for potting the sprouts up and a shop light to place them under. If roots have grown into the towel, you can just plant bits of the paper along with those roots if necessary.
For those of you who are interested, the bleeding heart pictured here (eximia) is a 40-70 type, though some other members of the same family are 70-40. Masterwort is also 40-70, but often begins sprouting just before it is moved to warmer temperatures. Lenten rose is 70-40, and usually requires at least one or two months at 40 before the seeds begin breaking open. Hellebore seeds won't germinate, however, if they've been stored dry for more than a few months. Hey, this is why you need Professor Deno's books! You can find them at the following links: