I love growing celery in our garden, so much so that I have a really hard time buying celery from the store. I’ve regularly had heads of celery 6 inches across and 2 feet tall. The flavor is so rich. I chop and freeze loads of it for winter use. You can even harvest the outside stocks for use before you harvest the whole head.
I plant my celery plants about 9-12 inches apart in full sun. If possible, I like to provide them with some afternoon shade. This helps keep the soil from drying out as much in the hot afternoon sun. Celery loves moisture so make sure you mulch it once it starts to establish.
If your garden is in full sun all day, think of something you could plant near the celery that would provide a bit of shade. For instance, I planted corn about 6 feet to the west of my celery last year. This provide some shade from about 3 o’clock on. Other great options would be trellised vegetables.