Disease resistance survey

Since 2007 I have pretty much quit applying fungicide sprays to my collection to prevent disease.* I have gathered data about the results with emphasis on identifying cultivars that prospered with little or no Blackspot infection. (I regard Blackspot as the single most destructive of the three major fungal diseases, as it has the ability to significantly weaken the plant, rendering it much more susceptible to freeze damage during Winter dormancy.)

I recognize, and wish to emphasize, that any list of highly disease resistant varieties compiled by one person in a specific region may be meaningful only to that particular site and/or geographic region. A cultivar that performed outstandingly in my garden may be a disaster in the South or the East, and vice versa. Keeping that in mind, the first group is a list of roses that I designate "Little or no infection". This group includes anything that kept at least 90% of its foliage even if it did suffer some Blackspot infection. Some cultivars had an infection rate of zero and these are marked with a +

William Baffin+
Mermaid+
Dortmund
Lady Hillingdon
Kathleen
Trier
Sidonie
Indian Love Call
Duchesse de Rohan
Cecile Brunner+
Marie Pavie
Salet
Clothilde Soupert
Pinkie, Cl.
Crested Damask
My Stars+
Basye's Blueberry+
News
Rosy Purple+
Westerland+
The Yeoman
Red Radiance
Blush Noisette+
Maria Leonidas+
James Mason+
Marie vanHoutte
Lilian Austin
The Green Rose (R. chinensis viridiflora)
Soupert et Notting
Tiffany+ (now there's a surprise!)
Penelope+
New Dawn
Mme. de LaRoche-Lambert
Konigin von Danemark
Great Maiden's Blush (some years it gets some infection and as such, would be placed in the second category.)
Tour de Malakof+
Ville de Bruxelles
William III+
Marianne
Ellen Tofflemire+
Nightmoss+
Souvenir de Claudius Denoyel
Marbree
Darlow's Enigma+
Wedding Cake (some years it fits in category 2 rather than here)
Pompon de Bourgogne+
William Shakespeare 2000 (NOT the original William Shakespeare, which has very poor disease resistance)
Renae+
Indigo+
Capitaine John Ingram+
Lamarque
Mrs. B. R. Cant
Precious Dream+
Little Mermaid+
Golden Wings (some years it fits in category 2 rather than here)
Star Magic+
Alberic Barbier+
Vineyard Song (some years this gets a + for complete immunity to Blackspot, 2010 included)
Basye's Purple
Russeliana
Dorothy Perkins+ (although, as most are aware, it Mildews quite readily from Mid-Summer on)
Banshee+
Errinerung an Brod (some years it fits in category 2 rather than here)
Gallicandy+
Blanc de Vibert (a very poor plant in most other ways, however)
Armide+
Buff Beauty
Excelsa+
American Pillar+
Joyce Barden
Mary Rose
R. centifolia cristata
Belle Amour+
Hebe's Lip+
Mutabilis (some years it fits in category 2 rather than here)
Veilchenblau
Hettie
Yellow Lady Banks (although none of the Banksieas are reliably Winter hardy here and have been removed from the collection)
Montecito
R. soulieana

Plus all of the Gallicas, with the exception of those that show conspicuous China or Hybrid Perpetual influence: these get some disease, often Mildew as well.

I include all of the North American species I grow as well. My R. clinophylla, two plants seed grown, from India, both suffer some Blackspot infection, although minimal.

List 2: Varieties that kept at least 75% of their foliage in spite of infection, and which outgrew disease quickly, with little impact on overall plant health.

Roundelay
Jeri Jennings
Distant Drums
Barbara Oliva
Incantation (some years it fits in category 1 rather than here)
Jayne Austin
Robert Leopold
Dick Koster
Reine des Violettes
Alice Hamilton
Rose de Rescht
R. damascena bifera
Charles Lawson
Souvenir de la Malmaison (although often plagued by terrible Mildew)
Sally Holmes
Mrs. William Paul
Constance Spry
Mme. Caroline Testout (some years it belongs in the 90% clean category)
Chianti (some years it doesn't belong in either group, as it does occasionally defoliate almost completely)
Sombreuil
Variegata di Bologna (sometimes it doesn't fare well enough to be on this list)
Marechal Niel
Yolande de Aragon (some years yes, some years no)
Violette
Portland from Glendora
Oshun
Sharifa Asma
Ghislaine de Felighonde
"Champagne Arches"
Smoky
Marchionesse of Londonderry
Pie IX
Verschuren
Kazanlik
Closer to Heaven
Belle Poitvine (and all of the "purebred" Rugosas)
Out of Yesteryear
Fakir's Delight
Linda Campbell
Sutter's Gold (some years not so good)
Golden Ophelia
Tradescent
Dragon's Blood
Violet Hood
Reveil Dijonnais
European Touch
Cuthbert Grant (This season it is one of the 90% and up varieties)
Floradora
Carlin's Rhythm
Soeur Therese
Hot Cocoa
Serendipity
Pelison
Fa's Marbled Moss
Savoy Hotel
Marchesa Bocella
Botzaris
Awakening
Mme. Alfred Carriere
Paul Ricault

The third list I have compiled is one assessing the many Miniatures I have in my archive, the vast majority of which are Ralph Moore hybrids. The following group indicates those which maintained at least 85% of their foliage at all times, whether infected with Blackspot or not. Some cultivars were totally immune to Blackspot in my garden and are marked with a +

Sweet Fairy +
Golden Century (near 100% immunity some years)
Blue Mist +
Hall of Flowers
Frostfire
Nurse Donna
Ora Kelly
Red Cascade
Red Wand, climber +
Tom Thumb
Magic Carousel
Cinderella (near 100% clean)
Magic Dragon
Apricot Twist + (reliably immune to all disease in all years tested)
Cal Poly +
Playgold
My Valentine
Rose Gilardi (near 100% immunity some seasons)
Glowing Amber
Magic Wand +
Sweet Chariot
Popcorn +
Little Meagan
Sequoia Gold
Red Alert
Red Germain
Little Buckaroo
Pinstripe
Stacey Sue
Star Dust
Splish Splash
Unconditional Love (near 100% clean some years)

I'm sure I have missed a few plants in compiling this list, which is easy to do when surveying a collection of over 2500 varieties. I'll remind readers that this list in no way in meant to indicate that all of these roses will perform similarly in all climates and in all sites/soil conditions. I know for a fact that some of the historic (OGR) varieties I list as highly disease free fare quite poorly in other regions. Still, it should at least provide some insight as to general health of the varieties listed.

*One exception to this is the Ralph Moore collection, which is one of only two or three complete collections of commercially released Moore roses to be seen anywhere. As the curator of such a collection I feel the need to continue spraying these to keep them in good health, as I have only one specimen each of the majority of these.

Transplanting tip #1

About working with R. wichurana hybrids.

One breeder I work with every year is Ralph Moore's 0-47-19, one of his most important hybrids used in the development of a number of his best roses. It is a cross of the species R. wichurana* and the old Floribunda from Tantau, 'Floradora'. ("Floradora' trivia: it now boasts 3466 descendants to its credit! Most of these come down to us through 0-47-19 and 'Queen Elizabeth')

I have found that there is a trick to raising seedlings from this first generation R. wichurana hybrid. They don't like to be transplanted from flats to pots at an early stage, or they tend to roll over and die. See that fairly large seedling in the upper right? Thats about the size these have to get before they can be transplanted successfully. So if you are working with R. wichurana or any of its first generation hybrids, you may want to let these get to at least the three leaf stage before transplanting them.

Oh, and one other thing: 0-47-19 has been my best hybrid for breeding Blackspot-free roses. I consider it a very important rose in the search for disease-proof roses. 0-47-19 was the seed parent for my 2009 repeat blooming Rambler 'Mel's Heritage', which is something like a repeat blooming 'Cecile Brunner', but more lax in habit.

*Yes, we are supposed to write the name as R. wichurana now and not the old spelling R. wichuraiana, which is now considered to be incorrect nomenclature. Classification systems grow and evolve and we have to adapt to these changes :-)

Towards immunity from disease: 'Home Run'?

With the introduction of Bill Radler's 'Knockout' about ten years ago, hybridizers have placed greater emphasis on the creation of roses with greatly improved immunity to the typical diseases that trouble garden roses, namely Blackspot: Diplocarpon rosae. Its not an easy task; Blackspot resistance is complicated and may involve multiple genes to accomplish. Of course, it IS possible, but a breeder can easily take ten years or more to achieve reasonable results. Fortunately for many of us, the groundwork has been done by several breeders and we have several lines of hybrids we can incorporate into our work. One of the roses I am working with that I have found to impart superior Blackspot (and often Mildew) resistance is Ralph Moore's 0-47-19, the old R. wichurana X 'Floradora' hybrid. However, it tends to breed a lot of pinks and whites, which has so far been a rather limiting factor.

More recently I acquired Tom Carruth's shrub 'Home Run', bred from 'Knockout' and involving 'Baby Love' as a grandparent. The latter is a five-petaled yellow shrub rose that is often used in breeding for disease resistance. Like its pollen parent 'Knockout', 'Home Run' is a triploid and only somewhat fertile. Its pollen will take on a limited number of plants and seeds are frequently infertile. However, in 2007 I made a successful cross of the old red Hybrid Tea 'Roundelay' X 'Home Run'. Why 'Roundelay', you ask? Well, here in my cliate it is immune to Blackspot even when not treated with fungicide. It is a shapely shrub of about 4 X 4 feet and blooms in clusters of deep garnet red 4" blooms. It does have some fragrance, but not very strong to my nose. Mainly, the Blackspot resistance was the thing that appealed to me most.

As usual, there were very few seeds from the cross, and even fewer seedlings. Two survived by the end of the season and were in fact growing very strongly and making an impression on me. The best of the two is the seedling pictured here. (Photographed April 20, 2009) This seedling has dark red tinged green foliage that is quite large and very healthy so far. The plant branches freely from the base and blooms in clusters, much like its seed parent. The photo does not do the bloom justice; it is a dark black-garnet red much like 'Black Jade' at its very best. From a beautifully scrolled bud it opens to a slightly cupped, 12 petaled bloom about 3 inches across. There is a modest fragrance that I detect. I will propagate this from cuttings and by budding this year to multiply the plant and to evaluate its ease of propagation. Now the deal is to find out just how disease resistant it (and its sibling) really is.

"Magseed"

I've been talking a few times recently about the results I am getting using Ralph Moore's breeder "Magseed", so I think its time I spoke a bit about it in more detail. This is a sister seedling to 'Linda Campbell', ('Anytime' X 'Rugosa Magnifica') the remarkable Hybrid Rugosa that can be grown to perfection in almost any climate. It is reported to prosper in zones as cold as USDA 4, and is probably good to zone 3 in a protected location. 'Linda Campbell' is however, sterile. Most first generation Rugosa hybrids are. (I regard 'Rugosa Magnifica' as a "pure" Rugosa, and that would make 'Linda Campbell' the first outcrossing into a very different line of breeding) "Magseed" on the other hand is quite fertile. As its name suggests, it does produce seeds, but it is far more fertile as a male (pollen) parent. It tends to make one or two seeds per hip, so unless you have a very large, mature specimen, work with it as a seed bearer is going to be very slow. Better to use it for pollen and work with a generous seed bearer.

I firmly believe that ideally, you should look at no less than 100 seedlings from any one cross to see the full breadth of what that cross can represent. Of course, you don't always get that opportunity; I make some crosses every year that result in hundreds of seeds, and then only five germinate. Bad combination of genes; can't always be avoided. I will make a few crosses using "Magseed" as the seed bearer, but the majority of crosses will employ it as a pollen donor.

What does it offer as a breeder? Well, based on my selections to date, it tends to breed large (6 feet plus) upright shrubs with bold, dense foliage, thick thorny canes, large blooms, good color (including some bicolors with paler reverses or a picotee petal edge coloring) and if you are lucky, a decent fragrance. Some of the hybrids I am currently evaluating have excellent Blackspot resistance as well. (I will describe 105-04-08 and other "Magseed" offspring in upcoming posts)

I think "Magseed" has the potential to breed a new race of hybrids that offer excellent shrub architecture (very important to me), improved Winter hardiness and hopefully, immunity to Blackspot, the bane of Rosedom.

The seeds they are a-sproutin!

Its that time of year; the seeds are germinating and I am starting to pot them up this week. Unfortunately mice are a serious problem where I am and so rose seeds must be sown in flats that are kept in a wire mesh "cage". Otherwise, the mice would sniff out the seeds, dig them up and eat them all. Yes, I've seen it happen. Thats why I do it the way I do now!

At left is a photo of some of the first seedlings that came up about four weeks ago. The cross is 'Rosy Purple', a Louis Lens Hybrid Musk X 'Vineyard Song', a Ralph Moore shrub that is very Musk-like in character. In my garden, both of these are almost completely disease free (the former is 100% Blackspot free, the later nearly so) and so I hope I might obtain some compact, highly scented, disease free shrubs that bloom in big clusters. 'Rosy Purple' often produces panicles of over 100 blooms all over the shrub. I don't know why this isn't a more popular rose; it is nearly an ideal garden shrub, especially since it is so disease free.

You can see in the photo that there appear to be two albino seedlings; pinkish, showing no evidence of chlorophyll. This happens with some crosses. Some of them will eventually produce chlorophyll and grow normally, and some never do and therefore they die. I potted up these seedlings yesterday and the pale seedling at the top center of the photo did produce chlorophyll, whereas the bottom center one did not, and so that one died from an inability to produce its own food. (These albinos survive only as long as the food stores in the cotyledons lasts)

Curious, eh wot?