I was at my Dad's, helping him in his garden, and looked across at an ajoining field. I noticed a strange patch of bright green among the winter grasses -- about three feet wide and 20 feet long.
"What's that green patch?" I asked Dad.
"Oh, I planted those leeks about fifteen years ago. I was going to expand the garden but never got around to it."
How many leeks had he planted fifteen years ago? Oh, he answered, about five or six.
Now this is an uncultivated field in central Texas -- hard packed caliche, scrubby mesquite, subject to frequent droughts, floods, fire ants, and all manner of things that want to kill you. If it were good soil, believe me, someone would have already cultivated it.
But apparently, leeks are like multiplier onions, if left in the ground, at least in our climate. And apparently, they can grow in cement-like caliche, without water or fertilizer. And, this is the most amazing thing of all -- deer don't like them. Seriously, this is astonishing, since this summer some deer started snacking on the needle-like tips of my varigated agave. This is the same plant that native peoples used to make needles that could pierce leather. And deer think this is a snack.
So, yes, I'd say leeks are pretty hardy.
I dug up a dozen or so, planted them in my garden, and hope to have a perennial leek patch of my own.