Onions - Growing From Seed - deep pots

There are literally hundreds of varieties of onions grown in this world, but unless you grow your own you usually have access to only a handful of varieties from the grocery store.  If you rely on growing onions from ‘sets’, (the little onions available from nurseries with about a hundred per bag) your options are often still quite limited.  Growing from 'sets' has other disadvantages too; often they will produce a significant number of ‘doubles’ (meaning smaller onions at harvest-time) or they go to seed, 
which makes them tough and unpalatable.   

Here is a guide you can follow that will ensure your success at growing onions from seed.

Onions going to seed.

Here in the Willamette Valley of Oregon (USDA Zone 7b - Link to finding what zone you are in), we do best to grow what are called ‘long day’ varieties which include Cipollini (chip-o-leenie) both red and yellow varieties, Southport White Globe,  or White and Yellow Sweet Spanish. There are many more varieties to choose from; check your seed catalogs or go online to see a greater selection. (Be aware that, if you wish to save your own seed, you must choose Heirloom/Open Pollinated non-hybrid seeds. Those listed above are all Heirloom varieties.)

You will need:

• Sifted potting mix
• Sand (optional)
• Pots: 4"-wide x 6"-deep (1 pot per 25 seeds)
• Seeds; start with fresh seeds each year; onion seeds lose viability within one or two years.
• Greenhouse or grow-lights, or the ability to bring seedlings indoors if in danger of frost.
• Plant-mister  

When to start: About eight-to-ten weeks from the time you wish to transplant them into your garden. We always get the seeds started around the middle of February. By late April the seedlings will be ready to set out into the garden.  They are ready when you can see a clearly defined "bulb", 1/8" to 1/4" pushing above the soil-surface in the pot. At this stage, the sooner they get into the ground the larger your onion bulbs will be at harvest time.  It’s always a good idea to have a bed in mind that you’ve prepared during the previous fall since it’s difficult to prepare beds in the spring if you have a long rainy season like we often experience here in Oregon. The seedlings can handle a touch of frost at this stage but its no fun transplanting them in really muddy garden beds. Some people wait until early or mid-March to start seeds and still have plenty of time for the onions to ripen.

Pots: We've found that starting the seeds in pots that are 4" - 6" deep is best. Any shallower and the seedlings become root-bound before it's time to transplant them.

Soil/Sand: Start with a good organic seed-starting mix.  It doesn’t need to be a premium potting blend, in fact, if you start with too rich of a soil blend you can experience a condition referred to as ‘damping off’ which looks like mold growing on the surface and which causes the young seedlings to rot as they emerge from the soil.  One way to help eliminate this condition is to sprinkle a thin layer of sand over the seeds.  By keeping the soil damp but not too wet and having good ventilation you shouldn’t have this problem. 

Onion seeds can be started in a variety of containers.

Fill the pots with a sifted soil to about 1/2" from the top (tiny seeds find it difficult to germinate in soil with large chunks of material). Level out the soil, tamping them down with the bottom of another pot to create a level surface so that all of the seeds will be sewn at the same depth (otherwise they germinate unevenly). 

Seeds: You may want to actually count out the seeds the first time so that you can have an idea of what 25 - 35 seeds looks like because that is about how many would be optimal to sew in 4" pots.  You can adjust up or down depending on the size container you choose.  The idea is to not have an overcrowded condition that would produce weak and unhealthy seedlings.  Place the seeds in the palm of your hand and pinch out a few at a time. Gently drop them on the surface of the soil, distributing them as evenly as you can without becoming too concerned about accuracy.  It’s OK if some seeds are touching each other. Sprinkle a sifted layer of starting mix or sand over the seeds at a depth of about an eighth to a quarter inch.  Tamp it down again and water gently (a planter mist-er works great at this stage). 

Watering:  Keep the soil moist using either a small spray bottle or water them from below by putting water in trays and setting pots in them. Tiny seeds, until established can be washed away with more aggressive watering techniques. Make sure you label them with the name of the variety and the date you started them.  Then it’s time to be patient, and let Nature do her work.

The seeds will not require sunlight until they have emerged from the soil, usually about two weeks from the time they are sewn, so you can keep them indoors where they will not freeze, on a window sill or in a greenhouse if you have one. Once the greens are up, they will require full sun. If you don't have grow-lights or a greenhouse, be sure to bring them inside at night if it looks like you may have freezing temps.

Teasing onion-roots apart before trimming.

Transplanting: Each pot of seedlings must be teased apart. You will need to trim back both the tops and the roots before trying to stick these tiny seedlings into the ground. You trim the roots so they're easier to slip into the holes and you trim the tops so that the pruned roots can support the greens above.

First, dump the whole pot into the palm of your hand.  Next, separate the clump into several sections (maybe 10-12 seedlings in each clump).  Hold one clump by its 'greens' and gently tap the root ball until most of the soil has fallen away.  Tease the seedlings apart and lay them back in your hand so that the small bulbs are in a line (see picture below). Using a scissors or hand pruner, cut away all but about 2 inches of the roots.  Trim the tops to about the same length as the roots. Now set the clump into another shallow container with a little water in the bottom to keep them from drying out while you prepare the rest for transplanting.  Prepare only as many as you are able to set out in one session.

Trim roots and greens to same length.

In the bed that you’ve already prepared you open up small holes about 4-5 inches apart. Our onions are usually planted in beds two to three feet wide, with several rows in each bed.  

Make holes: To make the holes you can fashion a planting stick called a ‘dibble’ from a smooth branch or a ¾ in dowel with a point, or, just use a ‘Sharpie pen’ to make the hole.  Make a number of holes and then go back and drop a single onion in each hole.  Gently press the roots into the hole and pinch the soil around each one, making sure the part that was under the soil in the pot is covered when you transplant leaving only the green top showing.  You’ll get the hang of it after a few and will be able to transplant hundreds in no time at all!

Onions in a wide bed.

Now the focus becomes keeping the bed weed-free and well watered.  Once the plants have become established and the warmer, sunny weather settles in you’ll be amazed at how fast everything grows.  Feel free to thin out your onions when they are immature and be sure to use the whole thing, greens and all. 

If you have planted non-hybrid seeds, hold back a few onions to replant next spring to save seed. Onions are biennial meaning they don't produce seed till their second year. By collecting your own seeds you can begin the process all over again, and saving seeds, dear friends, is one big step toward greater food security!

Link to another post we wrote about onion-growing.

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