Seed Starting--The Tough Ones

I  made a short presentation on seed starting at the last New Mexico Fruit Explorers meeting. I have since found my notes (!) and am going to take this opportunity to round things out.

Cleaning quince seed

Anyone can start veggie seeds with little difficulty. We've been selecting them to be reliable and easy for thousands of years, but today there's a lot of new interest in growing fruit and native perennials from seed--and these seeds can be tricky. 

Quince "slime" is good for skin--who knew?

Cleaning American persimmons

Seven days later

ALL plant seeds have some kind of inhibition mechanism that prevents germination, most have two, and some have more. Temperature, light, day length, moisture and any combination of these are triggers for germination. People, even professionals, gather seed and dry it carefully without realizing that half of all plants have seed that dies when it dries. This seed must be stored moist; some cannot be stored at all and must be germinated immediately.

To break inhibition seed must variously be washed, soaked, abraded, treated with vinegar or gibberellic acid--or none of the above. Some seed must be burned to germinate, some need to be eaten and "passed." Some seed requires oscillating temps over a period of years--think spring, summer, winter, over and over. Some can be chilled (vernalized) in the frig, some have to go through it au naturel. 

Any seed encased in pulp must be cleaned and washed. The pulp contains chemicals that prevent germination. Consider that in the wild fruits get eaten, or lie in leaf mold, experiencing rain, cold, etc. Some just need a quick rinse. The persimmon (pictured) took hours to separate from the pulp, and then was washed every day for a week, before going into a plastic bag of moist soil mix. Then it went into the frig at 40 F for about three months, and will be brought out to germinate at 70 F. I'll need to check it periodically because many seeds will start to germinate in the frig. I started a native viburnum two years ago, and it's just starting to germinate after several sessions in the frig. A native bane berry gathered in the wild and immediately stored moist in the frig germinated half a dozen seedlings in a matter of weeks, then nothing. After a return to the frig, then back out in 70 F, more seedlings emerged after two years.  So unless sources advise otherwise, always trial fresh seed immediately, even some like columbine or delphinium that usually require vernalization.

Another tricky thing some plants do--the radicle, the place where the root first emerges, germinates, then goes dormant until temps warm. You won't see top growth for six months or more. So be patient.  If I've given up, I'll dump seed into a cold frame, and have often been surprised.

Osage orange

Some plants set huge quantities of seed, most of which is non-viable. There is no embryo inside the seed coat, or it may not have matured. I gathered hundreds of the native Big Tooth maple, and perhaps six germinated. Native sumac may have only 50% viability. Some seeds are difficult to identify; I bought seed at a garden club sale, and there was no seed in the packet despite the entire flower head having been included. Seed is like snowflakes--no two are alike, from featureless specks the size of dust, to little hand grenades like the four o'clock, to enormous oblongs like the mango. There are millions of photos of seed online; make sure you get the right part of the plant.

One of the names most referred to at seed starting sources is Norman Deno, a professor who tested thousands of plant seeds for their optimum germination. In his book, he gives concise directions on starting many difficult plants. From his book, I learned that the American persimmon may continue to exude even after being washed for seven days. I learned that it germinates at 40-70 (50 % germinates in one to four weeks following a period of 40F with a period of 70 F. But outdoor treatment was fatal. 

Its good to know what cultivar you have--I'm still dithering over some buckthorn seed (he lists three), but which do i have? His book lists findings for all the seed he tested, and is available as a free download (see resources below).

Resources: 

Seed Germination Theory and Practice, Norman Deno--free download available at naldc.nal.usda.gov/download/41278/PDF--my first go to.

Prairie Moon Nursery--prairie moon.com  --Their catalog has a wonderful code for germination for all their native seeds, and great cultural planting instructions that aren't readily available elsewhere.

jlhudsonseeds.net --good starting and cultural info.

Seed Savers Exchange--seedsavers.org

theseedsite.co.uk  --UK site with a little bit of everything from photos to a junior seed site.

http://www.hardyplants.com/A.htm --from A to Z, a line or two of the most important bits.