Thursday, January 22, 2009

Saving Seed

There’s nothing like a cold winter day to get you thinking about spring. So last weekend when it was 2 below zero (still zone 6, see previous blog entry) I did a seed inventory. I was about to start filling out an order from my favorite catalog when I realized that I still had a lot of left-over seed. So I sorted and evaluated my stock. Wow! Do I ever have a lot of lettuce seed! Some of it from 2005.

The question is: will that seed still germinate? It depends on the species and the storage conditions. In the case of lettuce, my references say it is one of the best at remaining viable… maybe 5 years under good conditions. My left over onion seed from 2003 on the other hand, is mostly dead.

What are good storage conditions? In a nut shell, cool, dry and dark. About 40 degrees F and very low humidity. Temperatures in your fridge are fine; the enemy is moisture. Sealing dry seed in air tight jars with silica gel packets or another moisture absorbing material is best. Dry powdered milk might be handier for many of us than silca gel. Just put a couple of tablespoons in tissue paper, seal with rubber bands and add to your airtight seed storage jar.

Is that how I store my seeds? Sadly, not. They’ve just been in the garage… dry but subject to a range of temperatures and fluctuating humidity. So I’ll lower my expectations. Experience tells me that for most species, germination percentage may be down but enough of the seed is viable enough to warrant keeping it. Just sow a bit thicker than with fresh seed. If I had the time (or if the stakes were higher)I’d do a germination test by putting seed on moist paper towels at room temperature and recording the percentage that sprout. I probably won’t get around to that either.

Ok, here’s what the books say about seed longevity under good storage conditions. 1 year : onion, parsley, parsnip. 2 years: okra, pepper sweet corn. 3 years: bean, carrot, pea, broccoli, spinach. 4 years: beet, cabbage, cauliflower, eggplant, pumpkin, tomato. 5 years: collards, cukes, melons, lettuce, radish.

Note that what happens is that germination percentage declines over time. They don’t all die at once. And storage conditions have a big effect. One reference I read described seed of many vegetable species with germination rates over 50 % many decades after being put into ideal storage.


Julie Buehler said...

I am new to Yardley, PA after living in upstate NY for many years, where we dare not plant until Mother's Day! Over the past week, I have been wondering if spring comes in February to this region. I have not even cut back raspberries, roses, etc. Can you give me a timeline estimate of when I should cut things back, when non-hardy little plants can go in the ground, etc? Thanks!

Scott Guiser said...

Welcome to the sunny south. Perhaps this will help you get orineted to the Bucks county growing season... The "frost free" date for Yardley is May 13, about Mother's Day. This is the 90% frost free date which means that likely hood of a frost after this is very slim (10%). The 50/50 date is April 25. Flip of a coin whether you'll have a frost after this date.
Of course this is of primary concern for frost sensitive plants like tomato... cool seson crops such as the cabbage family, lettuces, root crops can all be planted earlier.
As far as pruning goes... late dormacy is agood rule of thumb for most plants so later this month, go to it.
Finally, the winter low temps in upstate NY were likey colder than here. You probaly saw -20F there. You will not often see temps below 0. This will allow you to grow plants such as peach, crape myrtle and others here. See Jan 14 blog on "how cold was it".
Want to be added to our bi-monthly gardening newsletter? Drop me a note.

Anonymous said...

thanks, Scott! that helps. I'd really appreciate receiving the gardening newsletter - can't find anywhere on the site to send you my email address.

Scott Guiser said...

Julie, Call our office at 215-345-3283 to sign up for a heard copy or visit our website and read the gardneing newsletter