RHA Newsletter 6(1): 8-9 (1975)

Paul Jerabek

There is no doubt that this is one of the most difficult colors to work with. Just note that not a single yellow hybrid tea or grandiflora has an ARS rating over 7.8, and only 'Peace' has a higher rating in the yellow blends. As a class, winter hardiness is poor and I have discarded many varieties for this reason. Not only is the yellow color recessive, requiring yellow ancestry in both parents, but there are thought to be several distinct types of yellow inheritance factors. Many early yellow varieties were strongly susceptible to blackspot, but this is not necessarily true of modern varieties. With the above in mind, I would like to comment on a few varieties I think are worth considering as parents.

SUNBLEST (Landora) Sets seed very well and is said to winter better than most yellows. A good grower. Appears to go dormant after it sets a good crop of seeds. Would favor 'Summer Sunshine' as a pollen parent for its great color and re-blooming characteristics.

SUMMER SUNSHINE. Sets seed reasonable well. Great color. Said to be tender but has wintered better than 'King's Ransom' for me. Could use better form. 'Peer Gynt' or 'Peace' might be considered as possible pollen parents.

PEER GYNT. Classed in the yellow blends but almost pure yellow for me. Very healthy plant. Long-lasting blooms of excellent form except for being a little flat in profile. Did not set any seed. the first year and may have to be used exclusively as a pollen parent. Worth trying on 'Summer Sunshine.' 'King's Ransom,' 'Apollo,' 'Eclipse,' and 'Sunblest.'

APOLLO. Despite its low ARS rating, I feel this variety has considerable potential as a parent. Needs more petals and a longer lasting bloom. It is vigorous and healthy, blooms well, winters well so far, and has large buds and long sterns. Fair as a seed parent. I like to cross it with 'Peer Gynt' or 'Peace.'

ECLIPSE. One of the hardiest yellow hybrid teas. I have plants over 25 years old. Sets seeds fairly well. Needs only a few more petals to be outstanding. How about a cross with 'King's Ransom,' 'Peer Gynt,' or 'Peace'?

KING'S RANSOM. Our winters are hard on it and the plant has to struggle the whole summer to come back. Fair as a seed parent. Great color. Worth crossing with any of the hardier yellows. Needs better form in the late stages.

PEACE. A deep yellow 'Peace' would certainly find a place in my garden, and who can say that a cross with 'Summer Sunshine' or 'King's Ransom' is not worth a try? Peace sets seed much better cross-pollinated than self pollinated.

ARTHUR BELL. Although classed as a floribunda, this sets seeds extremely well, has hybrid tea parentage, and J. Sheridan of London, England, says he has had considerable success with it. Needs more petals.

Three yellow climbers which have hybrid tea ancestors are worth considering as hybrid tea parents:

CASINO. Dr. Buck recommended this to us in Dallas for hardiness in the yellow class. Light yellow, many petals, but flat in profile. A haunting fragrance different from any other rose I know. Sets seeds well. Worth crossing with many hybrid teas.

ROYAL GOLD. The late Conrad O'Neal recommended this very highly to Melvin Wyant. Gorgeous color, superb seed set. Good form—needs a few more petals. Not very hardy for a climber but satisfactory for a hybrid tea. Tends to go dormant in summer and re-bloom only a little in fall, at least when carrying a crop of hips. 'Summer Sunshine,' 'King's Ransom,' 'Peer Gynt,' 'Peace,' and 'Sunblest' might all be used with this one.

GOLDEN SHOWERS. Sets seeds well and could be used as a source of slightly more hardiness than the average yellow hybrid tea.

Since the climbing characteristic is usually quite persistent, more than one cross to the hybrid teas might be necessary.

Space allows me only to scratch the surface of the possibilities. In studying Modern Roses VII, I am amazed how often yellow seedlings come from crosses on 'Pink Parfait' and 'Queen Elizabeth.' Since most yellow roses are light on petallage, one might do well to reach into other color classes with yellow parentage. Even 'Karl Herbst' is listed as a parent of a yellow rose.

Two final observations. Seed pods on yellow roses are often slow to color up and may even show very little color when ripe. Cutting the hip with stem and leaves attached and ripening under artificial light in water is a useful technique. Tender varieties require a shorter after-ripening period than hardier ones and my best results on yellow hybrid teas have been obtained with about 30 days at 33 to 38 F.

Feed-back is urgently requested. Let the editor (and me) know where I have missed the boat.

CybeRose note: The lack of hardiness that Jerabek noted and the tendency to go dormant (or at least stop growing for a while) during summer heat are consequences of the "cold tolerance" inherited from Rosa foetida. That is, the species and many of its descendents do most of their growing at low temperatures — a fault also found in some Chinas and their derivatives. The short-lived foliage of R. foetida suggests that the species prefers to go dormant — leaf-shedding dormant — in summer, following its fairly brief growing season. This inherited tendency is directly related to the blackspot susceptibility of so many descendents that do not go fully dormant in summer. Short-lived foliage, repeatedly produced by continuous growth, lacks the "built in" resources needed to fight infection.

A possible solution would be to cross "tender" yellow Teas and Noisettes — those that grow mostly in heat, resting at low temperatures—with the Foetida derivatives to counter this cold growth/heat rest tendency.

One possibility that has intrigued me is the fine yellow Tea-Noisette, 'Marechal Niel'. Mature wood of this old rose can endure winter cold. The weakness is that it does not go truly dormant. Brief warm spells during the winter can start it into growth again. The sappy new shoots are zapped by the next cold snap, which weakens the plants. If this is repeated a few times during the cold season, the plants may die from exhaustion of their nutrients.

But if the cold intolerance of 'Marechal Niel' could be combined with a true and persisting dormancy of a yellow Foetida derivative, the resulting progeny could escape most late Autumn and early Spring frosts by refusing to grow in the cool weather. Risley (1958) found that when he used 'Diamond Jubilee' (a Marechal Niel seedling) as pollen parent with 'Skinner's Rambler', the seeds were slow to sprout — suggesting an unwillingness to grow at low temperatures.

Heat and Growth Bibliography