Celery is a c ool season crop that should be started indoors ahead of time 10-12 weeks before the last frost. It can be set outside a couple of weeks before the last frost, usually around the end of April or beginning of May. It love a fertile soil with plenty of compost added. I keep my celery watered during dry spells. You can also start plants in early summer and set them out for a fall crop in July. The best thing about growing your own celery is that you can harvest a few stalks, complete with the dark green, delicious leaves, all throughout the summer. Home grown celery has a stronger, more robust flavor. I grow celery in my garden every year. You should too.