genetics is one aspect

choosing the plant according to site conditions the other (that means: identifying all important factor correctly and then gather enough knowledge to pick a "good" plant).

growth habit is a third, some species clump, some have short, other have long runners.

IME in a garden setting resilient clumping plants with "elastic" demands to their site (that is very tolerant regarding soil, hours of sun etc) work best, combined with some spreading by runners or seeds as "emergency task force" mending holes in case another plant dies and leaves a gap behind.

the actual quality of a plant is yet another factor, tissue cultured plants can be iffy, but then it seems standard for quite a wide range of garden plants. Some nurseries grow their mother plants in polytunnels, sothey are not as hardy in the long run, I think.

the size and quality of the root ball is important, flowering perennials in a huge gallon pot is a sure way to have a slowly dying specimen

I don't know if it's my first concern, but it is something I have in mind when I plant shop. I tend to stick with the old tried-and-true cultivars for a couple reasons, the first being if they've been around that long they've proven themselves, the second being in many (not all) cases pollinators prefer older varieties, and supporting pollinators is important to me. That being said, I do sometimes buy newer varieties of things for whatever reason, but it's not my usual MO.

BTW, I've purchased gallon perennials more times than I can count, and I disagree that larger specimens = dying specimens. In some circumstances they are much harder to establish (say, when trying to establish under a mature tree), but most of the time they're fine and I prefer large pots of stuff if I can get them -- I don't have much patience with trying to get in filled-in effect.

I grow annuals, hobby breeding of zinnias specifically, and vigor is big on my list of factors I look for. And speed of growth is a factor in the vigor equation. Of course, they are ornamentals, so they should look good while they are growing fast and vigorously. And probably no one is growing pigweed as a hobby.

ZM

Perennial, it is great to have a healthy happy plant which can equate with vigor. I have had small vigorous plants and sickly looking large plants. Here, I think it is trial and error as to what plant loves it's spot. I've had plants do well in what seemed like a poor spot and the reverse. I like large plants too.

Vigor is certainly not my biggest or primary concern when selecting plants. It is only one of several factors I take under consideration. And unless one is familiar with the plant already, how in the world can one judge vigor by looking at a plant in a nursery?? It will be just a guess based on appearance and may or may not be proven to be so once planted.

And it may be different in different parts of the country but smaller than gallon sized perennials here are only available very early in the season at retail nurseries/garden centers and only for specific types of perennials. Otherwise, it is always gallon sized pots and sometimes even larger. Most of the perennials I buy and plant are 1G pots and never, ever was there any issue about them thriving just as well as a smaller sized plant. It is certainly not the kiss of death and I'd say that if it was, it's a problem with the planter, not the plant!!

@gardengal that's why you do your homework before you buy new plants. And if it's a new variety that had just come out that year (or even the year before) I probably wouldn't even consider it. Also, being familiar with the species also helps. I've seen enough echinaceas to know what a healthy echinacea looks like (just as an example). This of course is also assuming the plant isn't suffering from sort sort of disease. But if it's a plant that frequently gets sick that would just be another reason not to buy it.

Actually, I also prefer smaller plants, probably because I plant the whole plant, media and all. Thus less of the peat mass rootball to grow out of and into the native soil. I have less issue with small plants than larger, and frankly, I hate to dig a big hole. It's quite easy to slip a 2 1/2 or 4 inch pot mass into a hole, versus having to really dig out a gallon sized hole. Yes, I'm lazy....but I like it that way.
And given that I tend to plant in fall, by spring the plant looks like it was gallon sized.

I've gotten into growing annuals and perennials from seed recently. It's so much fun and so satisfying. And also cheap! Of course, you can't get seeds from the patented cultivars that are grown from tissue culture--so I'm self-selecting just through that. I'm interested in natives for pollinators and birds and annuals to fill in color and bloom in my "dead" times. When I buy actual plants I'd like to get something that'll set seed for me to collect and play with.

Vigor is super important in roses to me! Or maybe I should say black-spot-resistance? Yeah.

After gardening personally for going on 50 years, working in the nursery industry for 20 or so years - and for a number of years as the perennial buyer - and working as a professional gardener/designer for nearly 30 years, I do very little research anymore. I've grown, planted or sold pretty much everything on offer locally :-)

I still have a hard time understanding how one assesses vigor in a nursery setting. It is a measurement of healthy growth so until the plant has been planted for a full season, there is not much to evaluate before that time span. Unless, as I said, one is already familiar with the plant in question. Buying plants that look 'sickly' in a nursery setting is never an option and I'd question the quality of the nursery if that was what they were selling.

There are some perennials I do avoid, simply because I know their performance in our climate will be iffy at best.

And unless it is a groundcover or some types of sedums, you just do not find 4" perennials available here after about the beginning of June. And never 2 1/2" ever!!

Totally...with an exception or two. Yes, the red Profusion isn't quite as vigorous or durable as his yellow brother, who isn't as vigorous as his orange sister, but I use all three.

I don't usually buy from nurseries and grow everything I use every year from seed, but even when I collect from my own garden for seed for the next year, I'm choosy. Weak plants that flowered poorly don't get chosen as parents for the following year. And, statistically speaking, they're less likely to have contributed pollen to the other plants as well, so that's good.

Natural selection plus my forced selection means that, after many years, weak, poorly-flowering plants are practically unheard-of. Things that try to consume passing animals and neighbors are the rule at hand.

But even when I do buy from nurseries, that's easy. Look for plants that look good rather than picking the one that looks bad. Easy-peasy. If they all look bad, that's not a good selection. And like you said, get off one's duff and do one's homework on a plant beforehand, or take advantage of modern tech and whip out one's cell phone (I don't use one, personally, but most seem to). Or there's always asking a question of the usually-very-knowledgeable personnel.

I do risk new plants, usually two to five every year, even first-year things that haven't been available before. But I also have 2,000 square feet of garden. If I lose 20 plants...you won't even notice, and I'll get enough volunteers just from self-seeding Melampodium to fill that right back in during early June.

Some make the cut. Most don't. But it's always fun to try.

GG, I know places I can get small plants that rotate through stock during the year. I also grow my own from seed, some of which (like a miniature japanese allium related to chives) are still in 2 1/2 pots despite growing a full season.
I don't dare yet plant, because it's abysmally dry and it's easier to water pots than run all over the garden watering newly planted things daily. I really do want to start planting stuff though :(

Some perennials are too vigorous (=invasive) and fancier less vigorous varieties are often better behaved. Sometimes it feels like a plant is either weak or a thug, rarely the perfect equillibrium.

For roses, I want a rose to be able to outgrow disease and weather damage but I certainly don't want a shrub rose to throw octopus canes or have climbing tendencies. This is very location-specific because what is perfect here could be too weak in a colder zone and too vigorous in a place with warm summers.

Dbarron--so are my baby desert rose (Adenium obesum). https://www.gardeningknowhow.com/ornamental/flowers/desert-rose/caring-for-desert-rose-plants.htm

They were started much earlier this year, are currently in 2.75" pots, and might make them out of those next year. They're very slow-growing, and very slow to start, and may even spend the winter dormant. My third-year plant just graduated into a six inch pot, which it doesn't really need, but I like the looks of.

Plants grow at their own pace. :-) Small doesn't mean they lack vigor. it just means small.

It sounds like we're talking about flowering plants*, and in that case, the flower is the most important part. That is, if the flower looks the way I want it to look then the plant can look like a dead twig.

Edit: Things bought specifically for their flowers. Some flowering plants I buy for their foliage, and in that case, the foliage is most important, but I still wouldn't necessarily look for "vigor".

I normally try to check cultivars online as DG or other sites. That said, sometimes I'll try something because I love the color or the flower form. A large part of my purchases are from online nurseries because I really prefer small plants. If your soil prep is good, they will grow and it is a lot easier to dig a small hole. Plus with some plants (roses, daylilies, irises) there is just no comparison to the variety you can find online versus a local nursery.

I also find that tried and true varieties often are not available at my local garden centers - they are selling the hot new plant.

Fall is the about the only time I can find small plants locally. They are sold as "window box" plants. They are fresh stock and about 5-6 dollars. But will they develop a good root system and make it through winter? That's a crap shoot.

Of course you can get small plants in spring from mail order for $15 plus postage.

It depends on where you are. Fall is ideal planting time for most things where I live. Late spring, just before the heat, not so much, except for real heat lovers like lantana and border line hardy plants that need time to settle in.

I can get native wildflowers in small pots for about $2.50 each. Slightly larger (4 inch) for about $4 each. Pretty much year round, though I've never ordered in mid-winter. These are typically available both mail order and local delivery for me. Postage has became insane (imo).

I have to disagree that the bloom is the most important thing (even in a plant that's grown for it's flowers). I want a plant that will be healthy and survive for years to come. I don't want a weak variety that will only survive one or two years before it dies.

Only problem is that varieties perform differently in different areas so that with all the variables, you have to see what works for you.

I don't want something that is actually going to croak, but if the flower is beautiful again and again, though the foliage is poor, the plant is good in my books.

It can even be an interesting contrast. For example, I have started growing day lilies from seed. It seems they don't grow true, so I kind of put them on the back burner. Then one bloomed scarlet red against this broken plastic pot and a half dead plant. It was quite stunning. And the day lily will almost certainly be back because they are incredible survivors... Now, if you consider that vigor--the will to survive--then I might be more interested in vigor.

Of course, when you get away from flowering plants, adversity can create stunning masterpieces--like Pinus longaeva that hangs on for a thousand years with just a thin strip of bark... We have a row of towering half-dead spruce separating two meadows, and I love to see them. We even have three dead conifers that I would not cut down.

I think vigor has its place. I wouldn't want a half-dead rose bush. But, vigor certainly isn't the most important quality all the time.

It all depends on many factors including the sun/shade levels, your zone/location, your watering schedule, and the soil-type. My method when moving to a new house is to plant a variety of things the local nursery sells and the plants I see in the neighborhood to test what does best for me. I have had a few plants, like rock roses, that should do well in my area, but they hate my soil or perhaps the drip irrigation that is provided. So I just move on to try something else. But sometimes I love a plant enough to keep trying. For instance, oregano loves my yard and grows and spreads (I have three different varieties) but culinary sage struggles, although you would think they would like the same conditions. But I love having fresh sage on hand for cooking so I keep replanting the sage next to the thriving oregano. The sage lives one to two years and then suddenly dies. I have tried a few sunny locations in my yard with the same results. But baby sage are cheap at the nursery so I pull up the old and put in a new one and treat it like an annual.

You say it depends on location, but if you meet the cultural requirements of the plant there is no reason why it should not thrive (unless it is a weak variety).

perennial, I know! You would think right. And certainly some strains of a plant will have less robustness due to their weak genetics. But I have been gardening a long time and it hasn’t been my experience that if I plant something that thrives at the house up the street that it will necessarily thrive in my yard. I suspect there are probably always differences in how people take care of their plants and slight variations in the soil or how much shade ect. But something I have often wondered about is the concept of “plant companions” and the opposite of that, which I’ll call “plant foes”. So whether a plant thrives or not could be as subtle as if it’s next to a different species that helps or harms it. There is a whole field of thought about “plant companions” and how one plant helps another grow. Certainly almost everyone knows that almost nothing will grow under a walnut tree. It is the ultimate “plant foe” creating a high tannin soil that prevents other plants from growing. So maybe my neighbor is growing a plant I covet next to its favorite “plant companion” and then I get a cutting from her and it fails in my yard because I planted it next to its “plant foe” which I am not aware is a problem for it. So my strategy is to try different plants in different places that should be a good location and if they fail I just try something else. I actually just stated a new garden at a new house 2 years ago. The landscape designer I worked with, who has decades of experience in our area, put in some excellent drought tolerant plants in my yard. She even steered me away from a few things I was interested in since she said “most of my clients say that doesn’t do well”. I guess they want refunds a year or two later if the plant dies. Almost everything she put in did fabulous, but one type of Westringia died everywhere in the yard except one spot against the foundation that thrives and spread vigorously. The soil is very uniform in the yard so who knows. Also all the rock rose hated my yard. For me it was no big deal. I just pulled the rock rose and unhappy Westringia and added something else. I love trying new things anyway :-)

Interesting discussion! I don't have very much luck with many things like Veronica! I also have tried fragrant flowers many many times and things that are blue and have a big fat failure on both counts. I keep trying though :-).

Stamina or staying power might be the words I would use to describe what I most would want my plants to have.

I guess that's because for me vigor is almost a scary word. So many things are invasive here and most of the invasive things have wonderful vigor. In all the wrong ways for where I live!

Tell me about it. Statice dies when I look at it. Spurge would take over the garden if I let it...

@zen_man - I just laughed out loud. And snorted. 'And probably no one is growing pigweed as a hobby.'