I have one seedling that I’ve kept for 6 years that is very prone to extreme vegetative centers. When it’s not doing that, it is a gorgeous bloom. Generally, the 1st flush in the spring brings on the massive display of the ugliest vegetative centered blooms you could imagine. After that, the plant calms down and puts out nice blooms. That makes me think that either 1) the plant is responding to the intense fertilizing regimen that one does in spring or 2) it’s responding to change in day/night length or 3) it’s responding to a change in absolute temperatures
There is a large garden of modern HTs at Lake Junaluska, a church affiliated resort/retreat up in the mountains of North Carolina. (It got a couple of pages in the ARS magazine several years ago.) It’s up about 5000’ elevation and is probably zone 5. The folks who care for the roses there are very good and get great growth and bloom out of plants that show major RMV signs on most of their leaves in the spring. Spring there is also the time of major vegetative centers on many, many of their roses.
What some of you think of as heat doesn’t really happen at Junaluska ever. So, for there at least, heat can’t be the cause of their vegetative centers for their first bloom (early June).
No, perhaps not “heat”, comparatively, but the more rapid flush of growth, either due to the increasing temps and quality/quantity of sun as well as increase in nitrogen from either applied types or bacterial breakdown of any organics which might supply it. It seems a function of accelerated growth combined with genetic proclivity, for whatever reason it occurs. Kim
Here is a photo of a seedling of Golden Angel from a pollination by Ballerina. On the left is a bloom with normal flower parts, on the right is a completely vegetative flower. The blooms ‘opened’ on the same day (yesterday).