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SEED TIME

Late this Year

This year I’m late, but not too late, with my seed orders. Usually, I get them in by a couple of weeks ago.

The only seeds that I’ll soon be planting are those of lettuce, arugula, mustard, and dwarf pak choy. They’ll fill any bare spaces soon to be opening up where winter greens have been harvested. No rush, though, because I have seeds left over from last and previous years of these vegetables, and they keep well if stored under good conditions.
Greenhouse greens
I’ve usually sowed onion seeds early also, in flats in the greenhouse in order to give plants enough time to become large transplants. Large transplants translates to large plants out in the garden before long days force them to shift from growing leaves to, instead, swelling their bulbs. More leaves before that shift makes for larger bulbs.

Last year, because of poor onion germination in the flats, I ended up getting fresh seeds and sowing them directly in the garden in early spring. Keeping the bed moist promoted quick germination and, by August, the bulbs stood up well, size-wise, to those from seeds sown in the greenhouse in past Februarys.

Seed Longevity

Onion and leek seeds don’t keep very well. Viable seeds are living, albeit dormant, embryonic plants which do not live forever. Conditions that slow biological and chemical reactions, such as low temperature, low humidity, and low oxygen, also slow the aging of seeds.

Seeds differ in how long they remain viable. Except under the very best storage conditions, it’s not worth the risk to sow onion, parsnip, or salsify seeds after they are more than a year old. Two years of sowings can be expected from seed packets of carrot and sweet corn; three years from peas and beans, peppers, radishes, and beets; and four or five years from cabbage, broccoli, Brussels sprouts, cucumbers, melons, and lettuce. 
Chart of vegetable seed longevity
Among flower seeds, the shortest-lived are delphinium, aster, candytuft, and phlox. In general, though, most annual flower seeds are good for one to three years, and most perennial flower seeds for two to four years. 

In a frugal mood, I might do a germination test for a definitive measure of whether an old seed packet is worth saving. Counting out 10 to 20 seeds from each packet to be tested, I spread them between two moist paper towels on a plate. Another plate inverted over the first plate seals in moisture and the whole setup then goes where the temperature is warm, around 75 degrees.

After one to two weeks, I peel apart the paper towels and count the number of seeds with little white root “tails”. If the percentage is low, the seed packet from which the seeds came gets tossed into the compost pile. (I don’t give them away!). Or, I might use the seeds and adjust their sowing rate accordingly. 
Seed testing
No one knows exactly what happens within a seed to make it lose its viability. Besides lack of germination, old seeds undergo a slight change of color, lose their luster, and show decreased resistance to fungal infections. There’s more leakage of substances from dead seeds than from young, fresh seeds, so perhaps aging influences the integrity of the cell membranes. Or, since old seeds are less metabolically active than young seeds, the old seeds leak metabolites that they cannot use.

Finally, Get My Orders In

Today I dug out my shoeboxes of seeds from the unheated workshop and noted what was missing and what was too old.

Needed still are yet undetermined, good varieties of Brussels sprouts, celeriac, semi-hot pepper, and melon. (Any suggestions for good varieties?) Also one or more packets of Bartolo cabbage, Blues Michili cabbage, Shintokiwa cucumber, Golden Bantam 8-row sweet corn, Blacktail Mountain watermelon, Carmen pepper, Mammoth sunflower, and Empress of India nasturtium.
Ordering seeds
And, of course, some tomato varieties need replenishment: Sungold, Anna Russian, Nepal, Carmello, San Marzano, and Amish Paste. They will join Belgian Giant, Pink Brandywine, Paul Robeson, and Blue Beech out in the garden.

A colorful and flavorful growing season is in the offing.

SEED LONGEVITY

Watching tiny, green leaves push up through the soil never ceases to amaze me, even after watching it happen for decades. And it’s all the more amazing with certain seeds, such as onions. It must be that I was scarred years ago by having a difficult time getting them to germinate. Well, I sowed them in the greenhouse a couple of weeks ago and they’re up and growing strongly. Most of them, at least.
My failure with onions years ago was due to old seed, and old for onion seed means anything more than a year old. Lettuce seed, in contrast, is one of the longest-lived of vegetable seeds and keeps up to 6 years. Here’s the life expectancy for other common vegetable seeds: 5 years for cucumber, endive, muskmelon, and radish; 4 years for beet, Brussels sprouts, cabbage, chard, eggplant, kale, mustard, pumpkin, tomato, turnip, and watermelon; 3 years for bean, broccoli, carrot, Chinese cabbage, pea, and spinach; 2 years for sweet corn, leek, okra, and pepper; and, along with onion, 1 year for parsley and parsnip. Under poor storage conditions — moist and warm, like my garage in summer — longevity is decreased.
Still, it seemed like such a shame to throw away good onion seed only a year old. So, in the seed flat a couple of weeks ago, a sowed one row of one-year-old onion seed alongside the rows of fresh onion seeds (and one row of leeks).
Confirmed: onion seed isn’t worth sowing after one year. In the seed flat are five neat rows of narrow, green sprouts and one barren row.
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Few seeds have as short a life as onion. More astounding is the longevity of some seeds, such as the 10,000 year old lupine seed that germinated after being taken out of a leming burrow in the Yukon permafrost. Just think: This same species was up and growing when humans first crossed the Bering Land Bridge, and saber-toothed cats and woolly mammoths may have brushed up against its leaves. Except that the story of the 10,000 year old lupine seed turned out to be apocryphal, as confirmed by radiocarbon dating.
The record for seed longevity is, in fact, 2,000 years and held by a date palm grown from seed recovered from an ancient fortress in Israel. But a recent discovery, once confirmed, will break that record by a long shot.
A kind of campion seed (Silene stenophylla) found buried, this time in a squirrel burrow, in Siberian tundra could very well be 32,000 years old. The seed has been grown into a charming, white-flowered plant.
Some coaxing was needed to get that original, 32,000 year old seed to sprout. A few cells, removed from the placenta, were grown under sterile conditions on a specially concocted growth medium. Once cells had multiplied sufficiently, the growing medium was altered to induce leaves, stems, and roots, and eventually the plants were robust enough to be planted in soil. The plant flowered and set seed, which germinated readily to produce more seedlings.
I wonder what seed has the shortest longevity. It’s not onion. Seeds in the family Tillandsioideae, related to pineapple, probably hold the record, with a viability of 4-6 weeks.
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