Yes exactly, fertilizer are all about growing a plant as quickly as possible for as little money as possible, so many miss out important nutritents for nutritious plants in the eye of profit. Edit: I meant to have the original comment here on the main thread woops, this is all I wanted to say here
nettle
joined 1 month ago
As somebody else said: it depends. Some fertilizers are shit and contain harmful shit but most are fine.
Here's some things to know tho:
If fertilizer gets on the leaves you must wash them before eating (which should be done anyway) as the residue may have toxic heavy metals (which may be there for plant growth).
Fertilizer is developed for maximum profits, only things that are needed for fast growth are added. this causes the plants to grow fast but with little nutrients needed for healthy long term growth. Its like plant fast food, it's cheap to make and will make you fat fast but your going to need more than just carbs fat and suger to be healthy.
So the plant will have less nutrients for us, and more importantly less flavour, for herbs like basil and celery the flavour difference is incredible.
for spinach flavour doesn't matter much. spinach also has basically no nutrients for us in the first place, in fact the oxalic acid in Spinach, when eaten, removes calcium from your body. So fast growing spinach has basically no downsides.
For a more complete diet I would recommend a seeweed based fertilizer (make sure it's sustainably harvested!).
Also sweet potato (Kumara) leaves are so so good. And easer to grow, and you get sweet potatoes, and they are healthier, and have much less oxalic acid. Only problem with them is they are not very frost resistant and require more light, if you want tubers, then spinach, (in low light it may not produce tubers but will still have leaves).