I grew this one 2 houses and 2 decades ago. I don't recall it being a prima donna. Do you have good drainage in this area. If you have heavy clay and the water does not percolate down in say a few hours, that could be a problem. To correct this, you would need to digging the soil down to 12 inches or more if you are able, and fill the hole half way up with a compost or a bagged 'Garden Soil' product, then add some of the removed soil and mix thoroughly. If you happen to have gypsum, you can add a cup or so into the soil mix. The gypsum will cause the clay particles to clump together to form larger soil crumbs, which will permit water to better flow through the soil matrix. You can then replant the rose.

Have you been feeding the rose? At a large public rose garden near where we live, many of the plants are 'growing backwards' because they have never been fed. If you have not been feeding them, then you can try this.

If you have extremely alkaline soil, this can be corrected by adding a chemical to acidify the soil. Two common products to accomplish this would be sulfur and aluminum sulfate, which is available at large nurseries.

I do hope that one of these will remedies will work for you.

John

As long as there is sufficient drainage, sufficient water, sufficient light and nothing is eating the plants (roots nor tops), nor are they either being damaged by freezes or fried due to too intense heat/sun, roses don't require fertilizing to stay alive or even grow and flower. If a plant is "growing backwards", there is (are) something (s) wrong, much more than just not having fertilizer applied to it. I grow literally many hundreds of rose plants of many types. Most are own root. Many are seedlings. They are all potted because I can't dig holes due to seismically engineered soil being too highly physically compacted. There would be tremendously insufficient drainage, even if I could physically create the holes. I've seen two foot deep holes excavated for construction in this yard. Water eventually seeped into them several inches deep. I don't fertilize and I don't experience any of them "growing backwards". Either those are the wrong roses for where they are trying to be grown or some other issue is at work, but lack of applied fertilizer is not it.

Thanks John and Roseseek for your thoughts!

The clay is not extremely heavy, and it's mildly acidic. I do fertilize at least once a year...plus the chickens make their own contributions :-)

Luckily I have another month before I need to make any decisions about what to try.

Maybe I'll dig him up and put him in a pot - he seemed to be doing well in the pot....

Look at what the differences would be between in the ground and potted...drainage, soil type, soil pH, temperature of the soil around the roots (hence bacteria and fungi activity and the amount of nutrients released from the soil by their activities), amount of oxygen available to the roots due to soil texture, etc. Any of them, singly or in combination, can make the difference between growing, stalling or shrinking. Good luck!