I have a friend (coincidentally named David) who was looking for Rhododendron 'David' and a few other older Rhododendron cultivars, and he couldn't find any nurseries that carry it. Additionally I've noticed many older neighborhoods in some of our cities have a number of large, mature, old specimens of certain plants (especially trees) that are nowhere to be found in local nurseries. I've noticed quite a bit of this in Bremerton and Olympia, and I'm sure a look around Seattle or Tacoma would reveal a similar story. I wonder if anyone has ever studied, or seen any kind of study, that attempts to catalog such plants, and possibly explain why they have fallen out of favor. Sometimes there are good reasons why garden plants should fall out of favor over time - for example, a disease-susceptible selection of something may be replaced by something resistant. Some (such as Rhododendron 'David') might be considered outdated because they grow too large for most gardeners, and it's possible to find something similar that remains 'better behaved'. But are there plants that fall out of favor for no apparent reason? (That wouldn't surprise me as I think there are a lot of plants that fail to catch on for no apparent reason.) I realize some of these plants may have been obtained from mail-order or specialty nurseries years ago. Still I have to wonder what I would find if I walked into a Seattle nursery 50 years ago. What did they have then that we don't have now? And to what degree were nurseries raising most of their own stock or purchasing it very locally? What plants have you noticed apparently used to be more common in the past than they are now? An interesting side project for me sometime (like I need more distractions...LOL) might be to start collecting some of these plants - or at least put together a larger list - with the goal of re-introducing them to northwest gardeners. I'm posting this on two other forums so pardon me if you see it more than once.
Subject to fashion same as architecture, home furnishings and apparel. Books have been written on which popular garden plants are associated with particular periods.
It might be relevant to look at older, second-hand gardening books and see what they are recommending, then looking at wholesale nurseries or retail nurseries, large ones, on-line to see if they carry them... Hortico in Ontario used to carry things I would read about in Nova Scotia, as classic varieties of this and that, but I haven't looked at their website for a long time, hope they are still going strong. Someone here told me recently that heathers are less fashionable as garden plants right now [I do notice fewer different varieties being sold than even a few years ago] -- but they do so well here in BC. The summer-blooming purples and reds that started flowering a while back are really glorious. Veseys on-line used to carry older varieties of this and that, and Corn Hill Nursery in New Brunswick has a website that is good for trees and shrubs that are hardy. My problems with Potentilla shrubs [early-pruned, now lush in leaf but not blooming much -- I had thought I'd read somewhere that they bloomed on old and new shoots] are an example -- I probably have an older variety which wants to grow large and since 4 or 5 were planted together in a driveway border, and I want to keep them "defined" in shape, I have a bit of a problem. Someone here told me newer varieties are often smaller. I like the concept -- the older favourites are fun to explore. They are often freely-growing or flowering, messy type plants by some people's standards; I took a walk around my Broadmead neighbourhood the other evening and was amazed at the number of really beautiful but very very highly-groomed, trimmed, shaped foliage gardens with a Japanese influence. Fewer colourful flowering plants. In downtown Victoria in the older residential neighbourhoods the more traditional English country colourful garden look prevails, with picket fences, other traditional features...
Here is a link to an article that might interest you: Plant trends 1987-2007. Also, Penelope Hobhouse wrote a book: Plants in Garden History. London: Chrysalis Books, 1992. Should be available at a public library.
In looking at this article, very kindly provided, I have noticed that the older street gardens of Victoria have lots of Aubretia [mentioned] along walls and in rock gardens in spring, but the Alceas [hollyhocks] are not mentioned although in the older English-style gardens of Oak Bay and James Bay one can see them in midsummer, along with other columnar-blooming perennials. These gardens are older than the period covered by the article. One should look at antique gardening manuals from the 1920's, 1930's and 1940's and '50's... There was a tremendous offering of various groundcovers here in Saanich-Victoria in the fall and spring of 2006/7 but many fewer varieties in the last two years -- partly, my theory is, that the gardeners discovered that they don't overwinter as well as hoped, don't take foot traffic as a lawn substitute as well as hoped, and small evergreen conifer shrubbery along with various ornamental grasses are lower in maintenance time and can be trimmed neatly on a mulched bed. Mulch is a fashion which I don't remember so much in the 1980's or earlier, nor to I remember my parents using it back in the '40's and '50's... except perhaps for mounded straw mulches used for overwintering perennials... there were garden "beds" then with soil to weed and hoe, perennials and annuals planted for cut flowers indoors, fences supporting climbing sweet-peas, beds of phlox [the tall phlox], pansies and marigolds... Irises and lilies had their day, too, I am not sure they are grown now as commonly. The fashion has moved in newer suburbs, anyway, to more of the "garden room" concept with low-maintenance gardens which can look well when trimmed and irrigated and don't require so much weeding and deadheading. The patio and barbecue is central. In past years, my parents' years, the wheelbarrow and other hardware often decorated the garden behind a shed or garage or even the back porch, now a fashion no-no with the outdoor fireplace room or barbecuing area taking precedence, which must look elegant and neat for entertaining... the flower garden used to be a working-in garden! People sat and drank their tea or iced drinks on the porch... Communications -- from magazines to television -- probably publicized tropical or semi-tropical holiday destinations where the sun-umbrella was a necessity adopted by residents in more northerly climates where porches were becoming non-existent; umbrellas and barbecues were a nice amenity to enjoying one's yard in summer... thus the garden room concept.
Re the Victoria & Oak Bay gardens...my son lives in Oak Bay. A few years ago, the Greater Victoria area had a very severe drought. When we visited, we noticed lots of gardens undergoing transformation in order to be able to exist on much less water. This, along with other reasons given by janetdoyle, helps explain at least some of the changes in plant fashionability. My own garden, in Vancouver (Kerrisdale), has seen lots of changes over the years. When I took it over, it had a bed of tea roses and lots of grass in the backyard. In the front was a large western red cedar tree right next to the house and box hedges planted in front of the house (where one might plant a border). The tea roses went when I determined that they barely got 3 hours of sunlight (rather than the minimum 6 recommended). The grass has completely disappeared from the backyard and I have lots of perennials, shrubs and small trees. In the front yard, the cedar was removed (I worried that it would fall and crush the house of my neighbour). The hedges were also removed. Nice borders, with new smaller trees, shrubs and perennials, are in place. The front was designed to be less maintenance than the back. I have been a bit of a plant junkie over the years and heavily into zonal denial (those really warm few winters sucked me in). That has changed since last winter...several plants of dubious hardiness here died and have been replaced - in some cases by native plants; in some cases by ones I know are hardy here. The next change will probably be to make the backyard less high maintenance (I'm getting older and can only spend an hour or two, rather than a full day, working in the garden). This is another reason for plant fashionability. For those in the Vancouver area who are interested in plant trends over the years, I would recommend going to the VanDusen Botanical Garden Library. Lots of older books there...and some old plant catalogues too. UBC Botanical Garden has a terrific library too, but it is only open to staff and volunteers. For other folk, look in your public library for older gardening books or have a look at used book stores (alibris & Powells are two online sources of wonderful old books...)
Your thoughts almost make me tear up with nostalgia for several of the old gardening books we dispensed with, inherited from my in-laws in Halifax, when we moved out to the Victoria area in 2006. These included one by a Martime garden expert based in the agricultural Annapolis or Windsor area "Valley" of NS, vintage 1930's I believe, whose name I will remember at some point, I think the surname was Fillmore, or Filmore, who was one of the early hosts of the CBC Maritimes program probably now defunct, "The Maritime Gardener" -- even I, as a child, used to enjoy listening to it. He had a lot of varietal names in the book, recommended and cautioned against, from tomatoes and apples to roses... and techniques, good old fashioned ones.