It was asked at market and I gave one answer and someone else gave another, so I could use some clairity.
Lordy, have we been down _this_ path before. I'm sure a GW search will turn up several discussions.
The simplest definition of an heirloom is that it's an open pollinated plant that has been grown for at least 50 years.
Some people use more restrictive definitions. For instance, there's a growing trend to use 1940 as the cut-off date, because it was in the 1940s that the big hybrid push began.
Others want to exclude varieties that were commercially introduced. Unfortunately, that would leave out a great many varieties typically thought of as heirlooms. For instance, all of the Livingston tomatoes would be excluded. So, too, would many of the great cucumbers. And even Brandywine, which is an icon of the heirlooms movement, would no longer be included.
Whether simple or restrictive, however, the common denominators are time in grade and being open pollinated.
Requiring heirlooms to be open pollinated leaves out the plants that are vegetatively propogated. For instance, apple branches are grafted onto new root stocks, new strawberry plants are grown from runners, garlic is grown by splitting the roots.
As I understand it, apples don't want to pollinate themselves. Yield is lower if pollen just drifts from one branch to another, and yield is higher if a second variety is used as a pollinator. So an apple seed has a good chance of producing a hybrid. If you grow out a bunch of apple seeds and find a great new apple then you could use grafting and quickly have a whole orchard of the new variety. Of course, you could spend a few decades of breeding to get a stable open pollinated variety that was identical to what you started with, but why spend the time and effort?
I was looking at a list of old apple varieties once and found that White Winter Pearmain, a little green apple, dated back to the 1200's. A variety 800 years old - and it doesn't qualify as an heirloom?
We could debate over whether these should be called heirlooms, but I suggest a new name for old varieties that are passed down vegetatively, something like "hand-me-down" or "inheritance" varieties. "Inheritance variety" sounds best to me.
Here is a link that might be useful: White Winter Pearmain
(Requiring heirlooms to be open pollinated leaves out the plants that are vegetatively propogated. For instance, apple branches are grafted onto new root stocks, new strawberry plants are grown from runners, garlic is grown by splitting the roots.)
The person asking the question posed it as a question asked at market and had I been answering the question I would have interpreted it as did Brook, that is, with regard to vegetables/fruits.
When discussing what an heirloom is for all flora that has to be propagated vegetatively, whether it be cultivars of perennials, or fruit trees or peonies or lilies, or whatever, one clearly has to use a different frame of reference to try and define what heirloom means.
Thank you, Carolyn.
Just to add a bit to the discussion, mistercross, folks have been wrestling with that issue for a long time. We could go the long way around, for instance, and just say it's a plant that grows true to type---which would include all the vegetatively propagated types.
People have used other terms in lieu of heirloom as well (I mean in general, not necessarily vegetatively propagated). Some that come immediately to mind are "heritage," "old-time," and, yes, "hand-me-down."
But in England, and I believe parts of the Continent, "heirloom" and "heritage" have different meanings when applied to plants.
BTW, garlic is not propagated by splitting the roots. It's done by dividing the bulb into it's component cloves, or from bulbils---excluding Dr. Simons experiments with garlic seed. The roots grow from the bottom of the bulb.
It's interesting, too, that you used garlic as one of your examples. With the exception of California Early (which was developed by the folks at Gilroy), all garlic varieties qualify as heirlooms---or whatever term you want to use for old-time varieties.