I don't think that 6 leaves is too terribly far behind, considering how far north you are.

I planted almost on time---about 2 weeks later than recommended for my location which is a lot further south than yours, and some of mine only have 7 leaves. However, most do have 9 to 11 leaves. A few have 12. We have had less than 9" of rainfall this year, and I haven't watered them much. They are doing especially well given the lack of moisture.

It won't hurt to give them liquid seaweed, but it is relatively low in nitrogen. If you want a quicker boost, you'd need to use something higher in nitrogen that is quick-release. Unfortunately, when you grow organically, one of the things you mostly give up is quick-release fertilizers with a higher N number. There's not much in the organic world that is high-nitrogen and quick release.

If you planted your onions into an area where the soil had been well-amended with compost, they likely will be able to get all the nutrition they need directly from the soil.

Because most organic fertilizers that you can use for top dressing or in a water soluable form are slow release and relatively low in nitrogen, when you grow onions organically you need to amend the soil really well every year prior to planting with organic matter like compost or very well-composted animal manure. If you need additional nitrogen (onions benefit from extra nitrogen because it is the number of their leaves and the size of their leaves in addition to the amount of water they receive that determines their ultimate mature size), it is best to work in some sort of higher-nitrogen soil amendment or fertilizer prior to planting---something like blood meal, corn gluten meal or soybean meal, for example. All of these perform best when incorporated into the soil prior to planting, and most of them can take a month to begin releasing their nitrogen....definitely not a fast boost type of fertilizer.

I don't know of any high-nitrogen fertilizer you could use to really boost growth that is organic in nature. People who use synthetic fertilizers normally use ammonium sulfate (21-0-0) or ammonium nitrate (33-0-0 or 34-0-0) to push onion leaf growth every few weeks, stopping the fertilization about a month before the onions begin to bulb up. Feeding high-nitrogen too close to bulbing time can cause the onions to have a very thick neck that will not cure well/store well if you're raising a lot of onions for storage.

My dad was not organic for most of his life, though he became more organic in his later years, and he always used a lawn fertilizer that was a nitrogen-only product and which usually had an NPK analysis of 33-0-0.My onions, grown organically, never achieve the size his did, because there is nothing available organically to boost their growth like the lawn fertilizer boosted his, so I just plant more than he did to make up for the fact that mine will be smaller, always, than his were.

I'm going to link info from CSU that lists the most common organic fertilizers and some basic info about them, including the typical release period of the macronutrients (usually 1-4 months) and their NPK analysis.

Dawn

Here is a link that might be useful: CSU: Organic Fertilizers

Thanks, Dawn. I do have some blood meal on hand, even though it's not fast acting I might add it as a top dressing. I have fish emulsion, so might do that too - there's always Miracle Gro to fall back on if absolutely necessary, too. I'm not completely organic, just try to be whenever possible, but I'm kind of winging it here so give myself some allowances. My soil is really pretty good there, but I did plant onions in the same spot as last year without doing much to amend it beyond what had been done last year.

You're welcome, Mia.

If you aren't trying to do it 100% organically, then I'd suggest you hit them with the MG to boost their growth. This is especially important if they are short-day types. My short days already are bulbing up so I couldn't fertilize them now if I wanted to, but if you have short day types and they aren't bulbing up yet, you could hit them with the MG to help them put on some quick foliar growth.

I have some warm-season flower, veggie and herb seedlings in flats that are very young and very small. I fed them with liquid fish emulsion this afternoon, which is 5-1-1. The smell of it almost killed me! I bet every raccoon in southern OK will be circling my greenhouse tonight trying to find the dead fish.

Dawn