New gardener - a few Qs & pics

Hi. Hopefully my pictures have uploaded properly. Firstly I am growing a draw full of veg/salad.. I think that is going ok. I have also planted some sunflower seeds (out of our bird food), as shown in picture, and I was wondering if I should thin them out? I have no idea what variety they are. Also, I have grown a lot of plants in pots. I was wondering how best to harvest salad, should I be continually taking a few leaves or can I harvest them all at once? If I take all the leaves at once will the plants die? Some of my plants have produced flowers (I think) and are quite leggy (like the spinach), should I get rid of them?

 

Salad crops will need spacing at around 6-9" apart.

I would give them about 18" spacing.

It really depends on what they are and the variety, with lettuce, some varieties can be picked as separate leaves, whilst most are picked as complete heads (which kills the plant). An old Lancashire miner showed me to cut the stalk of Cabbage in a cross after cutting the head. It then grew new leaves on the stalk, which were used as "greens". I've never heard of this working with Lettuce (might be worth a try).

I think you probably should, as the flavour is often spoilt after flowering.