Does heat cause vegetative centers?

This morning I noticed blooms on two of my crosses that this spring were normal and now after our record hot summer have blooms with vegetative centers. Does excessive heat cause vegetative centers.

Also have had a couple of pretty yellow crosses that first bloomed this year and also have vegetative centers. I am wondering if this will disappear from the blooms in normal temperature ranges?

Hi Joan,

I’ve read that Souv. de Claudius Pernet was notorious for two things, flowering nearly pure white in cool weather as it requires heat to form the yellow colors, and vegetative centers. I’ve had quite a few throw vegetative centers in heat. I’ve also had a number which threw them with any nitrogen fertilizer at all. Tequilla Sunrise threw them so severely, with such great frequency, I’d tease someone had walked by it with a sealed bag of fertilizer. That one could also have been heat driven as that garden was hot, but it also threw extreme vegetation with any fertiler at all. Queen of the Desert threw them in cooler temps, but the two gallon pot it was in did heat up, so who knows? Kim


Hi Kim,

I am noticing that Green Ice also has vegetative centers now. I am thinking that these are a response to the 85 days of 100+ that the roses have endured. It’s almost as if the roses are saying, I’m hot and I’m tired and I’m in no mood for anyone to put any pollen on me and ask me to set a hip.

I think I may take it easy on my Mother plants next year and not attempt too many crosses. They probably need a year to rest somewhat after the Summer of 'll.

Your Queen of the Desert is really interesting, actually quite pretty. Joan

I have not seen vegetative centers in the summer, but don’t live in the kind of heat you are referring to. But there are more than a few varieties that go vegetative in the winter- usually nights under 50 degrees or less. I have a seedling that has the most appealing flowers in summer, but when temps dip it goes all dirty mauve with huge vegetative middles. In summer it is a gorgeous pastel orange. Could be that the veg. centers are symptomatic of extremes?

I just had a thought, Phyllody is known in many plant types. When the State Ag people visited the Sacramento Historic Cemetery garden, they were quite interested in Viridiflora as one of them did her thesis on Phllody. Kim


I am convinced vegetative center are part genetical part viruses.

Then the virus crosses the placenta. Queen of the Desert threw them from its first flower. Kim

I’ll take a chance to try to interpret what Pierre said. I think he is referring to things like insertion sequences and other DNA pieces that move round the genome in very sneaky ways. They are a sort of virus, but not necessarily easy to transmit with a simple vector like aphids.

What we do know for sure in the case of Arabidopsis, and for all dicots in general based on that, is that formation of flower parts is controlled by a few master genes. The number of cycles of making sepals, petals, stamens and pistils is determined by their timing of turning on and off selected activities. So doubling, converting stamens to petaloids, and reverting back to stem and leaf growth (phyllody) is determined by the duration of signals in the apical meristem.

I believe that even the number of leaves produced before a flower is initiated is genetically very precisely determined, but by a counting function. A Rainbow Knock Out has only 2-3 leaves per flower, but Peachy Creeper in my yard this year had 42, while New Dawn had 14. In maize too this is a definite genetic trait. Lots of plants behave the same.

Sometimes a change in one of the master genes, by some sort of insertion/deletion upstream of the place where RNA starts to be produced, (or even within the RNA sequence itself),leads to putting a new switch into the circuit, or taking one out. Maybe the controlling protein, or RNA is temperature sensitive, or a different regulator can bind better or worse at different temperatures. Temperature control is an ancient regulatory function, which is critical to seed germination in very obvious ways, in temperate climates, along with daylength and presence of light. It may control some other growth patterns in ways other than simple speeding up and slowing down total biomass production. But daylength effects are more dramatic and easier to study.

The kind of definite phyllody that Kim sees, sounds like the function that is supposed to form pistils is overtaken by the leaf forming function. This may be the analog of Lfy, the leafy trait, in Arabidopsis.

Elliot Meyerowitz, when at Cal Tech did a lot with the control of flower pattern formation. I think you can find lots about it on a wiki.

Queen of the Desert wears a really striking crown, or is it a turban like in a turban squash?

I’d think more like a crown. There were flowers where there were only four or five traditional petals with the stamen and other petals replaced by the leafy growth. It wasn’t “pithy” like Tequila Sunrise and many others I’ve had. These were like feathers and actually quite pretty. I’d have grown it like a Viridiflora had the foliage health been acceptable over a greater period of the year. Kim

I’d say you have a very noble mutant, perhaps not Nobel level but still…


Thanks for the post. Now I will have to do some more reading and research. It’s like being back in Biology class which I loved. I feel 16 again.

I have to wonder, if some observe this in cool weather and I am seeing it in hot extremes, this is possibly some type of defense mechanism that is built in the DNA of the individual rose.

I believe it has been still discussed…


This UC Davis article also mentions high temps during bud formation. I have often seen Rouge Royale and Queen Nefertiti with gross phyllody/proliferation in the late fall,early winter here in San Diego. Since we do often get short periods of 3-10 days of obscenely hot weather called Santa Ana’s with the onset of autumn, the buds that are showing proliferation may be forming during the heat but showing up as full blown cases of phyllody 5-7 weeks later during cool weather—but are symptoms of the earlier hot weather. This weather pattern can repeat from Sept. to Dec. Totally makes sense.

Howdy all, here in Oz I find proliferations more common in the very early spring (sept/oct)blooms and by November everything sorts itself out and they disappear over the summer months, mind you the summer temperatures here are well over 100F. When autumn arives and then going into early winter, no proliferations are seen. It seems to be a early spring thing only.


Years ago I saw a few plants of a var submited for patent. A Koster by the so distinctive foliage whose flowers were all reliably freaky: oversized sepals, green crumpled petal and huge vegetative centers. The freak aspect was this plant novelty.

The plant was rejected and carefully destroied as the committee that implied some top rosarians considered it was the thing to do.

Alain Meilland was there and he knew how damaging this phenomenon can be. I.e. he had high hopes for a var named Romantica in Europe aimed at florist roses production and Tropicana derived (hmf pedigree is incomplete). After a while it started to have vegetative centers square buds and crumpled petals that never developed to full size so that the best flowers were ruined as was a beautiful var. I was among the first growers and met personnaly Alain Meilland on that subject.

Pierre I have two Bonica roses one produces a lot of vegetative centers the other does not. The one that produces vegetative centers clearly has a virus if not several. The other one appears clean. So I am inclined to believe you one the vegetative centers.

I have also had seedlings that seem to throw nothing but vegetative centers.

Ralph had a red mini he used as a promo for advertising many years ago. The center was full of green vegetative growth. He said it looked like a salad in a red bowl. They sold it as a “premium”, a freebie given away for subscribing to magazines. Kim

I have one rose that will reliably give vegetative centers if it gets any fertilizer at all. I use Miracle Gro for Roses as well as horse manure compost, and if this one rose gets some, it will proliferate like mad. Last summer the proliferations flowered–and themselves proliferated! This summer was not especially hot as summers here go.

Hi !

My Boule de Niege has lot of blooms with vegetative centers. It does not give hips neither. I have had it only two years, but I think it has more vegetative centers, if not given fertilizer enough. If it is for a virus, should I throw it away ?

One more thing, I have read, do not remember where it was, that especially noisette hybrids tend to have vegetative centers. I have two this years Crepuscule hybrids, and at least they are fine. Until now I have not noticed any vegetative centers, even if they have been in full sun 2/3 part of the day, also in the real heat.

The other one has bloomed madly, even with one big flush.

Now I looked it has three nice hips coming on it. Yes!

It even has a gorgeous, lasting scent. I am crazy for it.