To fish emulsion or not to fish emulsion

After the seed staring class I did recently, I got to thinking about one of the most asked questions I get- either at the class or just seed starting time in general. "When do I fertilize my seedlings? And do I use fish emulsion?"

I don't unless the need arises. The seedling has everything it needs until just after it develops its true leaves- not the first leaves you see (cotyledons), which look much different, but the true leaves. Now I do add some yummy stuff to my soil block mix- or seed starting mix. Things like rock phos, green sand, maybe some kelp meal, and alfalfa meal will take care of the nitrogen need- I also don't recommend fish emulsion automatically because it stinks- and starting seeds inside your house? Well, you can imagine...dilute it a lot if you do use it! So my seedlings usually have what they need for a bit since my mix has alfalfa, but what if I see this...

Borage in need of nitrogen

In the above image is borage. Some have very yellow leaves. It could be over wartering- another thing and common thing that can cause yellow leaves...but the three in the front have been treated with fish emulsion- which gives them a boost of nitrogen. This was taken a day after I gave the 3 in front a dose. Nitrogen is the one thing you'll read everywhere that everyone thinks seedlings need no matter what- really? Well, maybe not always. I've read on many blogs that everyone advises feeding seedlings fish emulsion automatically after the first true leaves emerge. I think this is incorrect, and I wait until I see something needs it. Right next to the borage is Hon Tsai Tsi and Kohl Rabi. It's hard to see in the pic but both are very green and don't need nitrogen. All these crops are made from the same batch of soil mix. The borage needs a little more nitro- the others don't. It's been my experience that plants that have too much nitrogen, given to green up their leaves, attract aphids- they love too much nitro- nurseries are guilty of this. So feeding nitrogen indiscriminately is a mistake, I think- and one I've paid for before, So to answer the question- no I don't automatically feed my seedlings fish emulsion unless I see a need for it and I've ruled out over watering- and then it's only plants that need it, not every the entire flat. Since I'm not a nursery, I have time to do this, thankfully. It is easy to correct though- since nitrogen washes through the soil, but a waste if it's not really needed.

Now one thing I do find that seedlings need, especially the first ones of spring, is rock phosphorus, which is why I add it to my seed starting mix. Cold soils of spring inhibit the plants ability to take up phosphorus- a nutrient needed for good root growth, something you want when you sink those new plants into the ground first thing in the growing season, but inside cold soil isn't an issue. So I get those roots strong.

Hope this clears that up! Happy growing!