The rose will tell you when it needs to be watered. Water immediately when you see the first signs of the ends of young shoots wilting. Main advice is to water slowly, deeply and less often rather than sparingly and often. This applies to all deep rooted plants not only roses. Best time for watering roses is very early in the morning.

PS. I live in one of the driest regions in Greece where the microclimate is borderline mediterranean and could be classified as semiarid according to the Koppen classification. What saves the day is the proximity to the sea which causes late night and early morning dew to occur for a large part of the dry season.

In combination with the kind of soil I have, the prevailing dry summer winds and the extremely intense solar radiation due to dry atmosphere, I would never be able to grow roses without supplemental summer watering. Average yearly rainfall here is about 300mm (12") which falls October-April/May.
Nik

This post was edited by nikthegreek on Sat, May 17, 14 at 16:46

Up until now, I've always put watering off as long as possible. This year it's been a relief, because instead of the rain basically stopping in March or early April, we've been blessed with a real spring,rain included. Naturally I water if I see wilting, but oddly enough that only has ever occured with a few plants! stil, once it starts getting fiendishly hot, I always have watered the new roses, once every 2-3 weeks, I'd say. But this year, I was toying with the idea of trying an experiment,especially since I want to move one of my tanks,and to do so must empty it....besides, I don't want to hoard the water; use it wisely, certainly, but not hoard it.
The principle would be the following: up until now, the plants are used to recieving a decent amount of water, but as rain ceases and temperatures rise,they must get used to these difficult conditions. But instead of forcing them to go "cold turkey",the idea would be to maintain the supply of moisture ,and GRADUALLY reducing it: i.e.,water now, wait two weeks, water again, wait THREE weeks, water, wait a month, etc.Up until now, I've had pretty good success,really, with my old technique, but since Nature has been so generous this year, I was thinking it might be just the right moment to try this new technique,in the hopes that the babies will arrive at summer's end much more robust than is usual,with zero cane burn, etc.
Btw," everyone" says to water early in the morning, but I am not sure I agree. To me, if you water in the morning,the sun soon becomes very hot,evaporation rate soars,so much of the water is wasted. Instead,in the evening, the plant has about 10 hours or so- the entire night- to absorb the water,without having the ferocious sun beating down on it,and drying the soil out before the water even manages to soak down to the roots! bart

The reason why I think that for roses watering early in the mornng is better than in the evening has to do with fungal disease rather than only with the most efficient watering method. If I remove this factor from my thinking I would suggest watering in the evening in retentive (clay) soils and early in the morning in less retentive soils.

You cannot, imo, apply a planned schedule, since watering needs are directy related to evaporation. This changes according to climatic conditions through the summer.

PS. In places or seasons where the barren soil gets overly hot during the day it is, in general, good practice (having to do with soil borne fungal disease avoidance) NOT to water before the soil has a chance to cool off somewhat. Which again means very late at night or early in the morning is a better option than in the early evening. I'm not talking particularly about roses but in general about good practices.
Nik

This post was edited by nikthegreek on Mon, May 19, 14 at 5:51

Sorry I'm a little late getting to this question. Bart, I don't really have an answer, because it's DH who does the watering. First, your idea of watering in evening instead of morning sounds convincing. We have dry coolish nights here, not the humidity that prevails in much of the U.S. in the summer, and I doubt watering in the evening would promote fungal disease.
I don't monitor DH's watering. But he's not a particularly orderly person, and I doubt he does his watering scientifically. He says he waters once a week, and my guess is, not very deeply. So your guess is as good as mine; better in fact.
About when we start. We got a lot of rain this winter and spring up until a few weeks ago. DH has watered once so far this spring, and these only trees he planted (against my advice) in the spring. We haven't started to water the plants we put in the ground in the fall and winter, but I'm thinking we need to start soon. There is rain in the forecast, but it starts in a week. We already have deep cracks in the ground.
I'm sorry I can't be more helpful! The best thing I can say that we seldom lose roses if we've prepared the ground well and if we planted them at the right time, by Christmas. Keep us posted on how your roses do. Good luck!
Melissa

I have no water at all in my woods so there can be no planting after March. Anything else is on its own....and so far, all is surviving....although the major difference, I suspect, is the fact that mine are all in part shade at least some of the day. I only planted bare-root roses in November and all the perennials I planted then are doing terrifically with no supplemental irrigation at all. Foxgloves and sweet rocket planted in spring is smaller than the autumn planted varieties (although this is not noticeable in my (watered) home garden since everything catches up....but not without extra water. I did chuck the washing up water on the forget-me-nots because some of them looked a bit mildewed. If you can arrange any sort of shading system for some of the day, this should give your plants the best chance....but essentailly, the key seems to be planting timing - as long as plants get a chance to get roots down over autumn, they will survive a summer with nothing other than seasonal rain (of which there is very little in semi-arid east anglia. My water problems are exacerbated by having very friable, free darining soil, certainly cuts down on impulse buys at nurseries.....and bare roots, including perennials, seems to be a viable way of adding to the planting diversity (or seed sown direct in late summer/autumn). Aklthough nothing is dying, they are all much smaller than they would be with extra water......but I expect once good roots have been laid down, they will be fine - thwe vast quantities of cow parsley, hogweed and nettles attest to the fact that plants will survive with no additional irrigation - timing is key, as well as size when planting.

Camps,
Semi-arid is a term which. although it has many definitions depending on which climate classification system one refers to, seems to me it cannot be applied by any stretch of the imagination to East Anglia. Drier than other parts of England yes, resembling many parts of the Med in terms of yearly rainfall yes, but with an average of 600mm yearly and a shortish, if any, summer drought period it cannot surely be called semi-arid. It doesn't even come close to the average dry med climate in terms of yearly rainfall and summer drought I think, not to mention evaporation potential.

Those numbers in the rainfall column in the link below (if it is accurate) would be 0 from June to September in a typical dry med climate. There are parts in Greece that receive more than 1000mm or even more than 2000mm(!) of rain yearly average, but what characterizes them into med climates (amongst other factors) is the extended period of summer aridity matched with great evaporation potential.
Nik

Here is a link that might be useful: East Anglia climate