"Roses are thirsty plants," I have been told. Of this location - which receives an average of 20 inches of precipitation in a year - I have been told "Roses do well here." And it seems a bit difficult to reconcile the first quotation with the second. Having cultivated roses here since 2012, I am learning that each saying has some truth in it. Some roses do very well. Others are just about impossible, at least without a strong supplemental watering program.
Somewhat more than a year ago, I was told by someone who had never seen my garden, that I was not watering my roses enough. I was skeptical. But I decided to see what would happen if I watered more. It wasn't a very strictly controlled experiment. So any conclusions I might draw from this are based on anecdotal evidence. Only very strong differences in performance across a number of cultivars from one year to the next could be considered as data that would strongly support the idea that more water would be favored by all the roses. With a good degree of certainty I know it is not true of all roses. But many roses had some positive response to this spring's warm weather and supplemental water starting as early as February.
I started watering more than once a week in mid March of 2017. I hand water, so I am pretty sure of where the water that I introduce into the garden ends up. And I have a good idea of how much water a rose gets - at least on a relative scale. In previous years, I would not water seriously until early May when it seemed like we were well past a time when frost would kill new foliage. Hybrid tea roses were the focus of the study because they were the group of roses that most conspicuously and consistently fell short of satisfactory performance.
When I started the experiment I had something like two hundred roses. My complete list of Hybrid Tea roses going into the season (list does not include ones that arrived in spring 2017) was: Leanne Rimes, Firefighter, Grande Dame, Double Delight, Melody Parfume, Charles De Gaulle, Moonstone, Gemini, Selfridges, Olympiad, Elina, Folklore, and Oklahoma. Olympiad had been in retrograde motion for a few years owing to pressure by nibbling animals. Oklahoma and Elina had not reached mid-shin height in two years. Double Delight suffered from having its roots nibbled and was nearly dead. Melody Parfume lived in the shadow of Crocus Rose and it is a great credit to the rose that it survived until I gave Crocus Rose a good pruning in spring of 2017. Selfridges grew vigorously everywhere it was planted, although it did prefer having its roots in the shade. And it did not do well when it got no supplemental water.
Leanne Rimes seemed to be complely unaffected by the extra water. Firefighter grew just a little more vigorously, though it produced no more flowers in the first year on the program. Grand Dame, Double Delight, and Charled DeGaulle died or were shovel pruned for TUPSBUBAR (taking up a planting space better used by another rose ) -- a condition that is worse than actually being dead and gone. Moonstone, Gemini, Folklore, and Selfridges did not behave very differently last year for the extra water. Had the experiment ended then, the conclusion definitely would have been that the extra water, if it did anything, killed tender HT roses. Not an auspicious start...
We had a strong monsoon last July and August with six inches of rain. Then from September 2017 through February 2018 we had essentially no moisture of any sort. By mid November the ground was dry and brick-hard and I did find myself watering the garden twice in November and once after Christmas. Until last year, the idea of doing that was unthinkable, absurd. But I think it saved some of my roses. I have in mind Mme Alfred Carriere. Most years the rose does not fully lose its leaves from the previous season when spring warmth has started it to set new leaves. But last fall, despite the weather being unseasonably warm, the rose lost all its leaves by Christmas. That caused me to fear the worst. This last week it has sprung to life. In all likelihood it would have done the same without water. But watering in early spring, I believe, will allow it to get off to a running start.
This spring I found myself watering roses through February and March because of the unusal warmth of the season. I had hybrid tea roses setting new foliage in January, February, and March. Not different HT roses, the same ones, setting new foliage over and over after light frosts. They would make new leaves, lose them to frost, and make more. Gemini was chief among these. Moonstone and Frohsinn (Joyfulness) behaved similarly. By the third or fourth round of defoliation from frost, I began to fear that the roses were goners. But within the last week, both have put out some very nice new growth. Moonstone's has been browsed by a furry animal (we're trying to make that determination...), but Gemini's is intact. Leanne Rimes' foliage has not been much affected by frost. But, so far this spring, the rose has been a little cagey about setting out a strong flush new growth. Browsing by some furry animal has broken a few pencil-thick canes. So the rose seems a little less happy right now than it has been for some time.
Olympiad, Folklore, and Oklahoma are making lots of new growth right now. It's with a kind of vigor I have not seen. My interpretation is that a little supplemental water in the spring has helped support spring root growth. That, in turn, is powering new foliage growth. But it is impossible to know whether the effect is due to water alone. Or if the unusually warm weather - the almost total lack of hard freezess since December - has either played a bigger role or worked synergistically with the extra water. Time will tell whether this level of improvement in spring foliage levels will correspond with improved performance through the season. It was, after all, the problem of late freezes killing roses that started us on the practice of witholding water - precisely to prevent premature foliage formation and the potenial for being killed from severe, late spring freezes. If we were to have a late, killing freeze we could yet lose several HT roses. And we'd have no clue whether they were made more vulnerable by the increase in early spring moisture levels. Conversely, if they do better we will not be sure that it was the water, alone, that did the trick. Or if it was more water combined with warmer and more consistent weather that did the trick.
What about other roses, the ones that are not hybrid teas? Crocus Rose just seems to be pretty much unfazed by anything. There was a moment during a particularly hot summer three years ago when failure of the monsoon rains affected it and one or two of its several dozen basal canes withered. Otherwise, it just keeps going. Extra water has made no perceptible difference so far. Something like this is true of Abraham Darby, Hermosa, Marchioness of Londonderry, Malvern Rose, Caramella Fairy Tale, Ascot, South Africa, Cherry Parfait, Lady of Shalott, Rainbow Sorbet, Baronne Prevost, Nouveau Monde, and Julia Child.
It seems to me that Europeana has been a materially happier with extra water. It's a rose that seems to survive on low rations, but produce roses in proportion to how much extra water it has: an ideal trait in a rose, IMO. I know that Claire Austin has been doing better for the water. Love has made a foot high new cane the diameter of shirt hanger wire. It's the first new cane in three years. By the standards of any reasonably vigorous rose this is a niggling improvement. By the standards I apply to this cultivar, it's a monumental achievement. The biggest difference seen so far has been obsered in the hybrid tea climbing roses. Looping, in one season, shot from a single five foot cane to three or four half again that length. America has been somewhat more subdued in its response, but it has put up new canes. . Antike 89 and Harlekin both fared better for the extra water as did Camelot. The King's Rubies set foliage much earlier this year, and there is hope that it will resume growingAnd Sexy Rexy made its first blossom ever. Some of the roses planted within the drip line of major trees were happy for the extra moisture. Nicole definitely needed it once or twice last season. Where a Folklore, a Generous Gardener, and a Pink Parfait are planted much to close to the trunk of a maple, it is supplemental water that keeps them from perishing, though their existence falls short of thriving.
As a control, last year I set out not to increase the water to Larissa -a Kordes shrub with a lot of noisette or multiflora influence. In fact, I tried to restrain myself from watering it at all. Larissa bloomed non-stop from May until frost. Was it covered with roses the whole time? No. But it always made a good show. I cannot recall any drooping, dead canes, or any hydration problem of any kind, not even at the cane tips. The only bad thing that happened was that it sent one or two vertical canes up above eight feet high. It was planted two years after Gemini. While Gemini remains a one cane wonder not yet four feet tall, Larissa is six feet in every direction and will require continuous, light pruning through this summer if it is to be kept in bounds. It will also need more severe pruning in winter. It will be the first rose I have ever pruned severly before reaching the five year mark in my garden.
So what can we make of this?
Hybrid tea roses certainly are thirsty plants. At least here in my garden, they seem to have somewhat more need of supplemental water than most other classes of roses. They also need weather that is steadily warm. When given adequate warmth and light, it seems to me, they do respond favorably to increased water rations. That said, it may be that one can extend the growing season here by about six weeks in the spring by starting a watering program early enough. And, perhaps, one can extend it a few more weeks in dry autumn weather by watering a little more in late September. This should have a material effect on the amount of growth a rose manages in a season. And that, in turn, seems to have a strong effect on a rose's ability to flower well the next season. If I am to cultivate hybrid tea roses here, I would need a few more seasons' data to be sure that the practice is working and that it does not increas the risk of loss to late spring freezes. It may be that if I find my hybrid tea roses to be producing lots of great flowers each season, the idea of providing a few extra inches of mulch in fall will become more appealing. While going to the effort, I could imagine I am encouraging a favorable result. That cannot be said now. Not with much conviction, anyway.
Floribundas seem a little less finicky about either moisture or chilliness. Most roses falling into the shrubby classes including David Austin roses, damasks, bourbons, albas, hybrid musks, and hybrid perpetuals seem even less affected by supplemental irrigation. It does seem to be useful to be sure that the soil is damp to a good depth when roses begin their spring growth spurt. For my zip code, that means that if it has not rained at least four inches between the winter solstace and the spring equinox, it's time to get out the garden hose and prep the rose beds for spring weather.
I may yet discover that springtime irrigation doesn't do much for the roses I intend to keep, but l can see that it has been doing a great deal for the iris. Introducing supplemental water to the spring garden starting as early as the month of February is going to be a practice of mine, so long as environmental pressures make it a viable choice.
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