What are some fruit or veggie plants I can grow on my window sill?

What were you thinking of? I would say maybe carrots, since they’re a root veggie and would be underground, but generally tomatoes or peas or something like that is going to toke more room than a window sill has to offer. How big is your window?

Or rather, how wide is your sill, how big are your pots, and how much weight will the sills support. Tomatoes, for example, need depth for root system to expand and strengthen. Lettuce grows fast from seeds but still needs depth. Herbs (H as in herb) would work; basil, dill, chives, mint.

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Gailcalled is right – a window box might be too small to grow most veggies. But spinach might do well, especially if you can go to home depot or a garden supply store and buy little starters (rather than growing from seed). Herbs will do really well – my mother has a window box in her NYC apartment and is growing basil, thyme, oregano, and rosemary – and all of those do really well in window boxes. Be careful with mint- the roots can travel and take over everything – so you might want to grow it in its own box.
Also, my personal favorite herb is lemon verbena. It’s absolutely delicious – you can use the leaves to brew really sweet and tasty herbal tea. I think it would do well in San Diego.