Seed Starting - Alliums

I used up my last storage onions last week.  If I can't quite grow enough to last me until the next year's harvest (or chive season!), at least I can make it to the next year's sowing!

I started growing onions from seed about 4 years ago. Previously I purchases bundles of plants from our local garden center, but decided I wanted the variety control and price savings of growing my own. Plus: they need starting 10-12 weeks before planting out, which satisfies my craving for growing, and keeps me occupied until I can start the fun crops later.  Also, per my extension office*, onion sets (the little bulbs you see at groceries and seed stores in spring) are not as good to use:

Planting onion sets is not recommended for market-quality onions. Sets are the second year’s growth of storage varieties or multiplier onions and therefore tend to be less sweet than other onions. In addition, they may bolt or go to seed early.

It took me a few tries, but I finally have a system I like for alliums.  I plant in 12-cell inserts. I like the depth of planting in full flats, but the divisions make it a lot easier at transplant time.  In the basement, I mix up some damp starter media in a flexible bucket, and fill my flats.  Then I bring them up where it's more comfortable in the kitchen for seeding.

Using three fingers as a "dibble", I poke 15 holes in each cell, and drop a seed or two in each. Allium seed does not keep well--especially hybrids--so if you are re-using last year's seeds it may pay to plant extra. You can always thin later.  This year several of my (new) fedco packs were held over from last year, and they gave me extra, noting a 75% germination rate.  So I double-seeded those quite a bit.

This is a little bit tedious, but three or four flats is a ton of onions (well--180 or so plants per flat!), and I can seed them all in less than an hour.  If you were doing this commercially, it probably wouldn't be worth it, but at this scale I find it manageable.  Onion sets can be $8-10 for 50-75 plants at our local garden center, and a seed pack (well more than a flat's worth) is less than $2!  I label each flat with some masking tape, cover with a plastic lid or a bag to hold in moisture, and put them someplace relatively warm to germinate.




Alliums don't like to dry out, so try and keep them evenly moist.  I generally water from the bottom for these.  After a few weeks you can feed with a mild organic fertilizer, or some compost tea. 

One nice thing about starting alliums is that they are fairly cold tolerant, so they are great candidates for growing out in a cold frame or hoop house, or even a sheltered spot outside if conditions are good.  Later in the spring when I'm running out of indoor light space I carry these out for the day.  It's definitely legwork but again, it's usually a time of year when I'm looking for excuses to go outside.  Just be sure to watch your forecast and your temperatures (a remote thermometer is a tool I can't live without): you don't want to cook them or freeze them. But once they've adjusted and begun to harden off they can take 40 degrees if they are sheltered.

There's some debate whether or not to trim plants to promote thicker stock. I've done it both ways.  Mostly, I think trimming is useful if plants are getting leggy and tipping over, or they won't fit under the lights!  Experiment a little and see what method you like. It definitely doesn't hurt to trim them.  Our extension office recommends trimming to 5 inches at planting time, which encourages root establishment.

The reason I like this size flat insert is that when it comes time for planting, I just carefully tip one pack out at a time, and gently tease apart the plants--their roots will be intertwined but they are surprisingly cooperative to untangling.  Individual plug cells were a total PITA to transplant (poking each cell from below with a pencil to get them out, arg!), and whole planted flats meant that I had to plant them all at once or have an awkward half-flat leftover.


The varieties I've sowed this year are:  Blue de Solaize Leeks; and Copra and Rossa di Milano onions.  I also have Redwings (picture above) on back order from Fedco.  Onions can be used at any stage of growth from scallions to full grown.  For storage purposes, they need to be cured (I use my same greenhouse table again for this, as seen above).  Some varieties store better than others, check your seed cadescriptions for details.

*By the way, I've probably mentioned our University Extension office a lot in these last posts, they are an excellent resource. I find that publications aimed at market growers are super valuable for serious home gardeners, with a little adjustment for scale.  There's an entire series of PDFs available for free on growing vegetables in Wisconsin, and much of what I've learned about Onions is from this one: http://learningstore.uwex.edu/assets/pdfs/A3785.PDF.  They include information from seed starting through to harvest and storage, and are of course appropriate for Wisconsin climate/soil types.