Have you heard of re-growing celery from a leftover stalk? (I'm almost certain I originally read this on one of your blogs; please do let me know so I can link to you as well).
I put this celery stalk base in a little bowl of water, and within a week it had regrown quite well. Then I put it in my homemade potting soil, mixed with a little compost, and there are beautiful new stalks growing.
When I had a leftover base from a bunch of romaine lettuce, I decided to give that a go in the same fashion, just for fun. And voila! It works for that, too.
I suppose it makes sense, given that celery and lettuce have a high water content. I wonder if there's any nutrient loss by successively re-growing things, but hopefully the soil remedies that. I also wonder what else can be grown this way...
It's just like pulling a rabbit out of your hat!