Oh, Jackie, thanks so much for the great report! I wish I could have been there. It sounds absolutely wonderful. I'll look for the book and the new nursery.

That would be the Hooks' new nursery? I hope they have albas.

Thanks for all the great info! I'm excited about the new nursery in Northern California!

mcnastarana - Do you grow albas? How is their heat tolerance? I am just ignorant, forgive me. The pictures are so lovely.

Jackie

Oops, forgot a question - do albas need winter chill?

Our experience has been that albas survive heat (our humid heat) very well, but they do need some chilling to flower. Ours never made many flowers.

On another matter: Do any of you have photos, especially of speakers and panels, from this conference, that I might use in a program to our Central Florida Heritage Rose Society? I have lots of pics of the gardens at the Huntington, but really lack speaker pictures. Thanks!

Thanks, Malcolm - I guess that rules out albas for me - if we get even frost 2-3 times a winter, it makes the front page of our local paper!

Jackie

Queen of Denmark will bloom with only minimum winter chill.

Nik I guess it depends on how you define "minimal." We're in a 150 chill units area, and I had 'Königin von Dänemark' for over four years. It made a big healthy bush, but not one flower, ever. We did get a few flowers every year on Alba Semiplena, as well as Felicite Parmentier, but just a few, and for just a week or two. So we gave up on them. Céleste produced one flower in all that time, and it was not a well-formed flower.

What is a "chill unit"?

Jackie

Jackie, It's a way of measuring how cold a plant has been, and for how long. The details were worked out specifically for peach trees, but lots of plants seem to follow the same system. Roses are odd in that they seem to need some chilling to flower, but they don't necessarily drop their leaves, whereas peaches won't collect chill units unless they are already leafless.

So here's the theory for peaches; probably some relevance to roses as well.

In summer, the plant is not collecting chill units. Once they drop their leaves, they begin collecting. The plant "collects" a "memory" of how long it spent at certain temperatures. We don't understand how this happens, but we know it happens very specifically in the meristematic areas of buds, and that the signal is not passed up and down the stem -- each bud must collect its own.

At temperatures below 32°F/0°C, no chill units are collected.

At temperatures between 32 and about 45 (7.2°C), the plant collects one unit per clock hour. (so for peaches specifically, a "chill unit" is defined as "one hour spent between 32 and 45°F")

At temperatures between 45 and 55 (12.8°C), the plant continues to collect units, but as the temperature rises through that range, it takes longer and longer to collect a unit. So at 45, it's collecting a unit per hour. At 50, it may take 5 or 6 hours, and at 55, collection has virtually stopped.

Between about 55 and 65 (18.3), no chill units are collected or lost.

Above 65, the plant begins to lose units, and the warmer it gets, the faster the loss occurs.

So in a climate like ours (Lakeland Florida) we may pick up 5 or 6 units at night, but then lose 3 of them the following afternoon, with a net gain of 2 or 3 for the 24-hour period.

Each plant is pre-programmed, genetically, to need a certain predetermined number of chill units to tell it that spring has sprung, and it's time to grow. So for example, a popular peach variety here is 'Flordawon', which requires 150 units. Upon collecting that many units, it bursts into growth. If you were to plant that variety in the North, it might collect enough units by Thanksgiving, burst into bloom and growth, and then freeze to death since winter is not over. On the other hand, if you planted a 700-unit peach that does well in Tennessee, here in Lakeland, it would go into winter dormancy, but then never come back out of dormancy, since its chill clock says it's not yet spring, after we've received our 150 units. So in peaches, it's really important to plant varieties appropriate for your chill units area (always published by state departments of agriculture and extension service).

With roses, as mentioned earlier, they don't truly go winter-dormant. In a climate like ours, we can force a growth flush on any class of rose with a light pruning and some fertilizer, even in December/January. So it is not "classic" chill that they're doing. Still, for some classes, such as Albas, Gallicas, Centifolias, Ramblers, etc., the decision of whether to make flowers or not, on any given growth flush, seems to be based on something similar to the chill-units model. In climates like northern coastal California, some of those "once blooming" varieties may repeat throughout the year, since they get continuous or frequent cold weather. So roses really are quite different in what they're doing, but for lack of a better term, we refer to what they need to flower as "chill units," which for them, doesn't seem to have a very precisely defined meaning.

Wow - fascinating - thank you.

My roses are almost all "warm weather" roses by now. I have some once bloomers, but they are also warm weather roes (banksias & hybrid giganteas, and one hybrid multiflora - Dawson's Apple Blossom- ID'd by Anne Belovich). When we moved in there was one small plant of Madame Hardy, which I understand is a Damask. It put up one new 2 ft tall cane each year, and last year's one cane died. Average blooms per Spring - 1 or 2, never any more. I finally took it out, and then later we discovered Sombreuil (Colonial White), which has blooms very similar to Madame Hardy, but loves our climate, blooms 10 months of the year here, and is trying to eat our house.

So, I guess we do not have enough chill units for Madame Hardy.

Our banksias do have some scattered bloom right now, which they do every Fall. Below are pics I took 5 minutes ago - I guess that means that they do get enough chill units to re-bloom a bit. I love roses - they do such weird and strange things!

Jackie

Another thought about the symposium (unrelated to the weather!). We visited the Banning house museum, built by Phineas Banning, who they say was responsible for the development of the Port of LA. My DH mentioned to me that he thought he had read about General (not a real rank) Banning in one of the books we have. When we got home, sure enough, he found it. In "Gods and Generals" by Jeff Shahara (the son of the guy who wrote Killer Angels about the Battle of Gettysburg, who has written several books about the Civil War also), there is an entire chapter concerning him. It seems that Winfield Scott Hancock (then a Captain), who was a General on the Union side in the CW, was posted in 1860 in LA as the local US Army Quartermaster. There was a depot full of Army guns, supplies, etc. in LA. However, there were no troops at all - just Captain Hancock. It was before the election when Lincoln was elected, and some of the local citizens (of Spanish descent, who were very unhappy about California being in the US) wanted to take advantage of the political chaos which was starting. They got together and Hancock was warned that they were going to attack the Army depot & seize the supplies. Banning organized a group of friendly citizens to aid Hancock (who had by this time sent an appeal for troops, but they had not arrived yet), and they successfully defended the depot all night, and the cavalry (literally) arrived the next morning. I remembered from the tour that Banning named his son Hancock Banning - isn't that interesting?

Jackie

Great summary (summery) on the Heritage Rose Foundation conference at the Huntington in San Marino. Agree on everything -- tour, lectures, garden. As I said to Malcolm, if we didn't have him, we'd have to invent him. Anita did a terrific job. I attend many garden conferences, and this fit right in with the best. Plus, we spend some time at the Huntington and other Pasadena spots, and we've found a great new (mid-century modern motel) place to stay. Plus, plus, can't get more charismatic than our leader Steven Scaniello. Oh, maybe a certain Boss. What a wonderful array of gardens and events our Foundation keeps up. On to the Hollywood Cemetery in Virginia! and may all our friends in Florida, Georgia, Carolinas be safe.

Malcolm, the chill hour info is very interesting. I've never heard the possible differences with roses. California has chill hour info on a website - http://fruitsandnuts.ucdavis.edu/Weather_Services/chilling_accumulation_models/Chill_Calculators/ - Sacramento/Fair Oaks ran from a low of 500 hours to over 900 in the past five years (temps between 32 and 45 degrees F). Jackie, it looks like you are a bit cooler if you are like Black Point - and Gregg's garden is cooler yet, hence his success with Gallicas. We have definitely seen better bloom on European OGRs in colder years. Many Gallicas and Albas have leaves that change color and drop from the plant in winter. Roses with Asian heritage hold onto their leaves, often "molting" by dropping their leaves after first flush in spring. We don't strip the leaves from China and Tea roses in the cemetery during pruning - we do for Hybrid Teas and Hybrid Perpetuals and take off the residual leaves on European OGRs too. I seem to remember Kim Rupert saying that Asian roses continue to store their carbohydrates in leaves and canes throughout the winter while the European OGRs pull them into the roots.

The problem with roses being different from the "official" (peach-based) model is that a peach tree will not begin counting units until it is totally leafless and dormant, a thing that a rose won't do at all, in a warmer climate. Yet in a climate like Gregg's, those leafy roses still make the decision to flower, based on some sort of chill. So it's a similar process, but not identical. And because of that, who knows if the exact temperature ranges, or the methods of counting "units," all of which are based on the peach model, are precisely valid for roses.

Interesting! I was familiar with chill hours for apple and other fruit production, but this is a new view of it for me.

In my own garden some European OGRs flowered well, Celestial and Celsiana being prime examples, but many others flowered poorly. And I have noticed that some of them decline year by year.

Sole reason I'd like to live in a climate colder than my own is to grow a certain Alba.

Jackie, do I have your permission to excerpt your summaries of the conference for the HRF newsletter? I can send you what I've written if you want to verify what I'm saying. I would give you a byline.

That is fascinating, Malcolm, thank you! From what I have observed, attempting to grow high chill hour roses in too-warm climates, they seem to behave similarly. Even when they have received what should have been sufficient "cold", the heat periods have appeared to have sapped it out of them. Inland, they would receive periods at and below freezing, with annual swings into long periods of heat, often nearly a hundred degrees higher than the deepest cold. Very few flowered well (if at all) and most grew backwards. Yet, put them down right on the coast in the "perma fog" and you get better flowering, at least for a while, though they decline badly due to the greatly increased fungal and insect issues. Right on the coast, "winter" lows were usually above freezing with many months long periods of "spring" where the temps would remain in a range of less than thirty degrees variation between the low and high periods, with the "extreme heat" happening very late summer to mid fall (by the calendar) and lasting a matter of days rather than weeks. Types such as Banksiae would flower just a few weeks inland, while flowering up to six, sometimes more, months along the water. (O'Neal Blueberry fruited for a few weeks in the mid desert 9b. It fruited for nine to ten MONTHS in the coastal 11a.) The only thing that made sense was, even though they received deeper, longer cold in the greater extremes zone, the higher (and longer) heat periods they endured seemed to negate the cold. The more extreme conditions also reduced the insect and disease severity, so their foliage was healthier and less adversely affected by pests such as aphids and sawflies than they experienced where they had to grow in nightly fogs and dews and temperatures which greatly fostered the fungi and insects.

I deliberately didn't bring nor collect any of the European OGR types to grow here in my new 9b climate with heavy coastal influence, so I can't compare how they may perform as they did in the 10b - 11a or inland 9b more "mid desert". I do have the species Primula, Hugonis, Xanthina, Fedtschenkoana, Serafinii, Stellata mirifica, Minutifolia and Banksiae and have observed "flushes" of "rebloom" on those I would expect to flower once (if at all) in the other climates yet lighter bloom on Fedtschenkoana, which threw flowers spring through fall in the mid desert 9b. Fortuniana here has pushed flowers most of the past twenty months, as has B. lutescens. Minutifolia flowers as reliably here as it did in both the mid desert 9b and 10b. Arkansana "Peppermint" pushed flushes of bloom here, too.

Anita - of course you have my permission.

Jackie