Jack, there is no, one answer to this question. There are a number of causes why that plant only developed into a Grade 1 while many of the same variety, propagated at the same time in the exact same way, grew to be Grade 2. Some varieties just will not make that many Grade 2 plants in the time allotted, no matter what you do. It just isn't in their genes. Some plants don't develop into the bigger plant due to graft issues ranging from a sloppy job with insufficient bud/stock contact or stock and bud incompatibility. Perhaps the budwood used to create the specific plant came from a degenerated stock plant caused by micro sports or mutations. Often this is how sports are discovered. A crop of pink Queen Elizabeth is budded and a number of them develop into white bushes, or pink climbers or some other variation. It has also occurred that less vigorous plants were created from degenerated bud wood.

At least three instances I've heard of have occurred where the resulting plants were actually more vigorous but with degenerated blooms. Angel Face, French Lace and Circus had instances where budded plants from the traditional stock plants created a group of significantly more vigorous plants with dirty colored or muddy colored flowers. You can still find the Angel Face mutation around, while it appears the other two have been cleaned out of what's available. At least no one is still complaining about them.

Perhaps the Grade 1 plants resulted from some cultural issue in the field. I remember Syl Arena of Arena Roses standing in the fields his crops were produced in, talking about having them "laser leveled" to insure they are as flat as possible. Irrigation is done by flooding the fields in Wasco, where many of the bare root production has been for decades. Making sure your field is as totally flat as possible makes it more likely the water will spread out evenly across it and all your production will be properly irrigated. Even though this particular field had been laser leveled, it had low spots where the water pooled and took far longer to seep into the soil, while other areas didn't get as much water and dried out faster.

He also spoke about having the field "ripped", a kind of tilling, where the soil is broken up to a good depth to allow the roots to develop better, deeper and water to absorb into and through the soil better in hopes of raising a greater percentage of higher grades of plants. Even with the leveling and deep ripping, he showed how this field had issues as evidenced by the oddly variable performance running across rows of varieties. You could follow whatever the issue was across the field as better plants grew on either side of the 'vein' which ran across the rows, with inferior ones growing in the 'vein'. He theorized it was a combination of ripping and leveling issues causing that problem. But, who really knows?

So, I would say, if the lower grade you obtained was due to the variety itself, or an easily corrected cultural issue, perhaps that plant may develop into one which can't be distinguished from a 'good plant' with time and appropriate culture. If the lower grade resulted from a bad graft, stock incompatibility, degenerated sport, viral infection, severe dehydration in storage, or some other more permanent issue, I doubt anything you're going to be able to do is going to make a difference.

I would also guess that very many of the "culls", the lower grade plants potted and pushed with a lot of fertilizer and sold off through home improvement stores, probably don't get the chance to do what they might be able to. From many years of observation and experience, many who are willing to buy a less expensive canned rose in a smaller pot usually aren't going to put nearly as much effort and care into the planting and growing of a plant which cost them a few dollars they will for one which cost them twenty or more. It is cheaper and no real loss if it fails, where the more expensive one hurts more if it fails. The cheaper ones are also frequently purchased to temporarily spruce up properties for sale, rental, or other needed short term improvement, then left to fend for themselves. The point being that whether or not they had the potential for improvement, they frequently aren't given the opportunity. Look around, particularly here where even the worst plant often grows, you can easily find the one cane wonders resulting from the cheap, pushed culls dumped in huge numbers through these types of stores. Worth the gamble? That depends upon your risk avoidance. Kim

Rose grades only apply at the time to newly harvested roses. Whatever they were, they'll always be.
That's not to say a grade 1 1/2 or 2 won't grow, over time, to be as big as a grade 1, but this has nothing to do with the grade at harvest.
Normally the better grade at purchase will develope faster and produce better, sooner, than lesser grades. Healthier roses (better grades) give you a bigger rosebush sooner.
The grading system only applies to grafted roses. Own roots aren't graded. The age or size of an own root is often mentioned but never a grade. Planted side by side, various grades and own root roses can develope over time to similar similar size bushes.
Regarding graded bare root roses, planting 2 grade 1 1/2 bushes together in the same hole can result in a bush as big or bigger as a grade one. The two will always each be grade 1 1/2.
To repeat, the grade is determined at time of harvest. and is only used as a selling tool. What happens after that doesn't change it.

WOW Thanks for the information. I'm really glad I joined this Rose forum, it truly is informative.
Jack

I used to buy the inexpensive smaller roses, pot them up with annuals at the base to sell at my garage sale. People really liked them and it got cars to stop and look at my stuff rather than drive by. I got to see lots of different roses in bloom as well that I might not have bought because of the price and shipping. I stopped doing this because so many were not the variety advertised on the bag. I did get a wonderful pink climber and a beautiful ivory Hyb. Tea by mistake however. They grew into big plants eventually and are reliable every year. Some others were so weak and never grew well at all even with the best of care.