I'm new to roses, but I've read that 5 hours of morning only sun is ok but the same for afternoon only sun is not. My roses only get morning sun for about 5 1/2 hours & are doing fine - but it also would depend on your climate I suppose.

Ljsemar,could you provide more info, please? Where are you located? How long have the roses in question been planted? I think it's true that only afternoon sun is a bit tricky for roses,but that doesn't mean it can't be done. One thing I notice: all the roses you've tried have large, full-flowered,many-petaled blooms (except Iceberg?). Small, single-flowered ones might do better. But please provide more info!

Interesting info,allielawson!!! I had no idea about the UV versus infrared thing, just assumed that somehow the afternoon sun was just "too hot". Also, your advice sounds good; my only reservation would be that the OP doesn't state how long the plants have been in place,nor where he/she is living,and both of these factors could be relevant. Some people who are fairly new to roses seem to expect them to behave almost like annuals; i.e., behaving as mature plants only a few months after planting. IME roses need much longer to mature; some are very, very scanty bloomers in their first or even second year. Also I don't think that KO roses are essentially different from other "landscaping"-type of roses. They fall into the category that I suggested: roses with small, single (or semi-double,in the case of KOs) flowers.

I garden essentially in a boxed in desert valley, but not in Arizona, in Western Pennsylvania, zone 5/6.

My only rose bed is bathed in sunlight from 10:00AM to 4:30PM. The rest of the time no direct sunlight hits it, being blocked by tall buildings, my "Brick Canyon's Walls".

I live and garden in the inner city. Radiating heat from an adjacent parking lot, street pavement, tall brick hospital buildings (across the street and next door), my house, patio and car pad, create the most inhospitable environment for roses imaginable. At 1:00PM it feels like Death Valley.

The roses wilt by noon every sunny day. Flower petals also droop on some varieties along with the foliage. Even green buds nod. Roses drop some developing buds in large clusters 'knowing' their elimination is necessary for the benefit of the remaining buds.

Yet, in spite of all this negative environmental pressure my roses thrive. I keep my roses well hydrated and heavily mulched, and practice the most attentive management measures I can come up with to reduce the roses' environmental stress.

You could say that I should not be growing roses under such stressful environmental conditions, grow something easier, but my rose garden is working. There has to be Divine intervention involved!

Moses

Or perhaps the strength of nature, which is divine enough

Thank allielawson! very interesting information!

Nature is not Divine. Nature's creator is Divine.

Moses

If you do decide to go another route, day lilies do wonderfully in that type of situation, although it would be helpful to know where you reside and how long the roses have been planted. ..

Knockouts will work well in pretty poor light conditions and some Kordes do fine. You might to try your luck with some of these.

I have found that my perennials that don't get any morning sun, but instead 5+/- hours of hard afternoon sun are not the part shade or even shade tolerant varieties, The ones that do well are heat and full sun loving plants. I would categorize 5 hours of strong sun as "full sun," especially if you are in a warmer/southern area of the country. If I were going to put roses in my gardens with hard afternoon sun I'd be trying a whole other class than "shade tolerant."

Moses .. it sounds like you're religious & I'm not so we might have to agree to disagree on how nature was created!

What's to disagree about, lol? It's all One.

wow, allielawson, thanks for all that info. Makes sense to me. For now I have just moved the 4 plants that were in the corner where there is the least sun out into pots...we shall see if they increase in their productivity before I make new holes for them.

I am in Austin, Tx, zone 8b. All of the plants that I moved were purchased and planted last spring from Chamblees. Since they are all own root I thought perhaps that was why they were taking longer to get established. However, other ones purchased at the same time are blooming and have grown substantially more with the exception of Madame Anisette which I've read takes a long while.

The ones I moved are Madame Isaace Pereire, Duchesse de Brabant, DA Mary Rose and Abraham Darby which had a very small root ball so it may be a goner. I also have a Heritage Rose, a Marie Daly and an Iceberg that I bought at local nurseries that are doing a bit more so I may wait on those especially since it's a dangerous time to move roses here due to the heat. I moved the 4 because they were at the point where I wasn't even sure they would make it either way and I hope their chances are better this way. I'm struggling to come to terms with their loss just so I'm emotionally prepared for the worst.

Now thinking perhaps I will turn that corner into a seating area, maybe get a corner fountain or a vine that can make it in partial shade. I do have a few knockouts that I could move from other areas in the yard, but will also be looking for all the wonderful suggestions that were given here.

As always, I appreciate the expert advice here. It's been 2 years since I first started rose gardening and my knowledge hasn't nearly grown to match my love or hard work put in. So nice to have access to the wealth of info here.

ljsemar,what part of Austin are you in? I'm in Cedar Park and just put in new roses this spring. So far the ones getting midmorning and early afternoon sun are doing great. I have some in the front that get about 5 hours of sun and they are doing great. Another group that I planted around the utility box all but one seem to be growing and putting on buds and blooms. They are a Lavender Veranda, Arizona, and Gold Glow. The Nacogdoches that I planted isn't doing well at all and will probably come out. This area gets full sun all day. The KO that I had at my old house got full sun all day and did really well. There are so many micro climes in the Austin area that what works for me may not work for you.

OK, this is good info,ljsemar. I'm very into this thread because I, too, have an area that only gets afternoon sun,so I'm looking for ideas, too.

I think you were right to pot up those that looked too peaky;that sometimes can save a rose. Also, using that area for seating, etc, is a good idea, too. But one thing I must throw in: IME, own-roots just DO take longer to get started, and I wouldn't completely write off the possibility of having at least a few roses in this area of your garden. I'm in Tuscany, Italy,also around a zone 8b,and in areas like these you can get away with a LOT more shade than you could in cooler zones, because our sun is just a heck of a lot stronger. However you might find it worthwhile to try to grow a rose up in a pot for a year or so before putting it out in this area of the garden. Actually,many people (myself included) find that raising a rose up for a year or so before putting it out in the garden (even in a prime spot) is always preferable,because the larger plant already has a more mature root system.I'm finding that even grafted ones do better this way. Own-root roses always struggle for me unless I grow them up to a fairly hefty size before putting out.

So, in the fall,I guess what I might do would be to pot up the roses that just don't seem to have been able to grow/ bloom much. I might think about buying a few new roses and grow them up in pots,choosing ones that have few petals and small flowers for the shady area. You needn't limit yourself to Knockouts. I have one spot where I think I get no direct sun until around 4PM or so,in which I planted a Narrow Water last fall,and it is blooming,looking fine!!! but the plant was a couple of years old. One thing that I find helpful is to look at the on-line sites of Peter Beales' Roses and Lens Roses. These are both very helpful, because in their descriptions of the various roses they include info about whether or not the rose can tolerate shade. I figure if a rose can take part shade in England or Belgium, it'll be fine in part shade here in Italy. But I would grow it in a pot for the first year or so anyway.

Ooh, how I want Lavender Veranda! I got a rose on-line that was supposed to be LV, but it was mislabeled; it's something yellow and orange red instead, yuck. I have to write to the nursery and see if they can replace it, but sad to say it's not in their on-line catalogue any more...

bart, I love my LV. I have one in the front of the utility box bed and 2 in big pots on the patio. They are blooming fools and they were just planted this spring. Love them and the Brilliant Veranda too. Char

The angle of the sun in the sky determines the amount of light coming from the sun. The light at noon in the summer is peak exposure time. The closer the sun is to the horizon the less sun light is received. 5 hours of light when the sun is high, should be enough for most any rose, however, 5 hours of afternoon light is not. Another important light source is reflected light bounced of light colored surfaces such as walls.

I have never read about a shift from UV light to IR light, but even if it is true, these are both invisible lights. I was taught that plants mainly depend on visible light for photosynthesis. Too much UV light is harmful to plant growth, this one of the reason why people are worried about ozone depletion.

Afternoon sun can be hard on plants when the temperatures are high because it can cause water stress. Delicate sun perennials that wilt with too much heat do better with afternoon shade. I have never found roses to be that delicate.

I grow many roses in less than ideal sun conditions. I find that they grow slower and take longer to start flowering. ljsemar maybe your plants need more time to mature.

Allie, could you share a reference for the IV versus IR content of the sun's rays.

Thanks,

thanks so much bart for your hopeful words! I won't give up on roses that are strong and mature being able to make it there, I will take your advice and try again next season with some robust ones. I can always run another rescue mission if it doesn't go well. Also I am reminded that while I adore roses, I truly love any plant that I can successfully grow.

And yes, Lavender Veranda is lovely in my garden so far, been blooming almost non-stop, absolutely purple and not mauve or pink at all. Been a great purchase. Though it is located in a more favorable morning sun area of the yard.

Definitely with own root roses, the only ones that are blooming prolifically are the ones that I bought my first season, 2 years ago. I have lots that are growing still, just not blooming tons yet. Patience, patience.

charintx, I am in Buda which is the suburb on the exact opposite side of Austin. I will keep a look out for what works well for you and be taking notes! Also noting what roses you may have purchased way way up there that I may need to make the trek to acquire myself.

We're about to get into the weeds but here we go:

stillanntn6b, Here's a UV index diagram from NOAA/ the National Weather Service. In the diagram, the blue line is UV dosage. As you can see, the UV line peaks in mid-day and falls off in the late afternoon just before 16:00 (4:00 pm).

Here's a graph that plots the spectral strength of light at sea level. Unfortunately, this graph is from Wikipedia. It's not exactly a proper academic source, but this is a rose forum, not a college classroom. Pay attention to the yellow dotted line in this diagram, it's a graphic representation of the spectrum of afternoon light. You can observe that the spectral power of the sun's UV (100- about 400 nm) is roughly half that of IR light (700+ nm) in the late afternoon.

As Valrose explains, plants use the visible light range for photosynthesis. This is roughly the same range that the human eye can detect. The reason UV light peaks between 10 and 3-4 pm is that it is highest in the sky (the widest angle) at that time. But, while the visible light range is responsible is photosynthesis, that doesn't mean that UV light is "invisible" to plants.

We used to think that plants could not detect UV light. We now know plants have UV receptors. However, UV light is so powerful that the plants use the UV receptors to protect them from potential UV damage. This process is akin to how human skin tans (produces protective melanin pigment) in response to UV damage. [I'd like to take this opportunity to remind everyone to wear their sunscreen. EVERYDAY. There's no such thing as a healthy tan; it's a bodily response to sun damage.] If you've ever seen a plant that turns red from sun exposure it's because it's producing a protective flavonoid pigment like carotenoids (the orange color of carrots, sweet potatoes and autumn leaves) that absorb blue (UV) light and anthocyanins in dark berries. And, of course, those pigments don't just protect the plants, they also serve as antioxidants that protect our bodies when we consume them. The human body is so well adapted to the consumption of these pigments in plants that we depend on them as vital nutrients. And yes, this is why the ozone layer is so important. If it is depleted, humans and plants would need more UV-protective pigment than we could ever dream of producing.

But IR is not useful to plants in that it is too weak to support photosynthesis and does not induce physiological responses like the flavonoid pigment production of UV light.

The National Institutes of Health's website has an article up that was published in the Journal of Plant and Cell Physiology. It details how a plant's UV receptors are essential to seedling establishment and can even help the plant tell time by regulating its circadian clock.

Allie- that is absolutely fascinating and thank you for taking the time to explain so well. Really neat!

Allie - I really appreciate the detailed info on the way that UV light is used by plants. I didn't know any of that.

I still not convinced that problem with afternoon light is a UV to IR ratio The UV index diagram shows a similar fall off of UV light in the morning as in the afternoon. The second graph that plots spectral strength does not compare afternoon light to morning light but I'm guessing that it would show a similar distribution of spectral strength.

I sense that the subject is absolutely interesting. It is a pity that the Google translator does not offer me a translation that I can fully understand. Does the afternoon light have more ultraviolet light? Or is it light bulging?

What a pity. I do not completely understand.

I understand that the afternoon light and the morning light are different but I do not understand why. I would love to speak English and be able to understand without translating. Thank you

Maybe this will translate: Assuming clear skies, the amount of UV is greatest when the sun is directly overhead and falls off in equal amounts the further the sun gets from overhead. If the sun is overhead at 12:00pm, then 11:00 am would have the same amount of UV as 1:00 pm, 10:00am as 2:00 pm, and so on. This is also true for the visible light which plants use for photosynthesis.

So is UV light important for plant growth? Allie says yes that there is research indicating that this is so. Allie says the UV light peaks between 10am to 3-4 pm.

I said that because it is hotter in the afternoon, plants may be water stressed and not able to use the afternoon light as efficiently as in the morning. I don't think that the problem is afternoon light quality versus morning light quality.

Hope this helps and that the translator can accurately translate this.

If I have made mistakes in the understanding of this discussion maybe Allie will be able to correct them for us.

I think that you've done a great job of explaining, Valrose.