Roses forum: What is This? Disease or other?

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Name: Kelli
Canoga Park, CA, Sunset 19 (Zone 10a)
Where summer is winter
Region: California Celebrating Gardening: 2015
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Kelli
Sep 9, 2016 10:00 AM CST
Is this a disease or just lack of water? This is on a 50+ year old Mister Lincoln bush, of which at least 3/4 of it died last year. The first picture is not the best but my camera gets persnickety about focusing sometimes. I think you'll get the idea. The first picture shows newer leaves and the second shows older leaves. Virtually the whole plant (what's left of it) looks like this.

Thumb of 2016-09-09/Kelli/965db1

Thumb of 2016-09-09/Kelli/96aa12

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Name: Lyn
Weaverville, California (Zone 8a)
Garden Ideas: Level 1 Garden Sages Celebrating Gardening: 2015
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RoseBlush1
Sep 9, 2016 1:15 PM CST
Looks like water stress to me.

If you have not given your plant a regular rejuvenation prune, the old wood at the base of the plant may not be able to move moisture up to the newer top growth. So, even if you have enough moisture in the root zone, the plant is inefficient in providing moisture throughout the whole plant.
I'd rather weed than dust ... the weeds stay gone longer.
Name: Zuzu
Northern California (Zone 9a)
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zuzu
Sep 9, 2016 1:20 PM CST

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It also looks like overfertilization burn. Have you used any fertilizer on or near this rose, Kelli?
Name: Lyn
Weaverville, California (Zone 8a)
Garden Ideas: Level 1 Garden Sages Celebrating Gardening: 2015
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RoseBlush1
Sep 9, 2016 1:37 PM CST
That's possible, too.
I'd rather weed than dust ... the weeds stay gone longer.
Name: Kelli
Canoga Park, CA, Sunset 19 (Zone 10a)
Where summer is winter
Region: California Celebrating Gardening: 2015
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Kelli
Sep 10, 2016 9:26 AM CST
Thank you both for your input.

I have used fertilizer a couple months ago. It was an organic fertilizer, if that makes any difference.
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Name: Lyn
Weaverville, California (Zone 8a)
Garden Ideas: Level 1 Garden Sages Celebrating Gardening: 2015
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RoseBlush1
Sep 10, 2016 1:58 PM CST
If you watered the rose well before applying the fertilizer, you should not have fertilizer burn as long as you followed the instructions.

The safest way to apply any fertilizer -- organic or chemical -- to a rose is to make sure the rose is well hydrated by watering it deeply the day before you feed your rose.

I haven't experience fertilizer burn in my garden, so I don't know how long it would take to show up. The water stress that I have seen was due to the long term drought we had and it looked quite similar to your photo.
I'd rather weed than dust ... the weeds stay gone longer.
Name: Sue
Ontario, Canada (Zone 4a)
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sooby
Sep 11, 2016 8:10 AM CST
I noticed in the pictures there is white residue or something that looks like whitish blisters. Has the rose been sprayed with anything?
Name: Kelli
Canoga Park, CA, Sunset 19 (Zone 10a)
Where summer is winter
Region: California Celebrating Gardening: 2015
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Kelli
Sep 11, 2016 9:20 AM CST
I don't remember if I had watered before I applied the fertilizer or not. It was a while ago, probably early summer, trying to get the plants to bloom again before the heat of summer, which didn't work. Drought stress certainly is possible. I water for an hour once a week with a soaker hose which seems like a lot, but I know nothing about how much water roses need. The soil is clay.

The rose had not been sprayed with anything. What you are seeing is just part of the dead foliage. It isn't raised like a blister. It doesn't rub off. It feels like part if the leaf. It is only on the top surface of the leaves. It isn't a hard water mark. I water at the base with a soaker hose.
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Name: Sue
Ontario, Canada (Zone 4a)
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sooby
Sep 11, 2016 11:09 AM CST
When the soil is dry I don't think an hour with a soaker hose would deliver enough water unless yours releases a lot more than the ones I have used here. The best thing is to check the soil with a trowel by digging a few inches down and if it's not damp at root level then keep watering until it is.
Name: Cindi
Wichita, Kansas (Zone 7a)
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CindiKS
Sep 11, 2016 11:56 AM CST
Did you have any fires near you? I finally realized my roses that are near our fire pit were not liking the smoke from our campfires. They had similar damage, maybe from something in the smoke.
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Name: Kelli
Canoga Park, CA, Sunset 19 (Zone 10a)
Where summer is winter
Region: California Celebrating Gardening: 2015
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Kelli
Sep 12, 2016 9:45 AM CST
Cindi, no, no fires here. We have a fire pit and have never used it in the 19 years we have lived here.
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Name: Lyn
Weaverville, California (Zone 8a)
Garden Ideas: Level 1 Garden Sages Celebrating Gardening: 2015
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RoseBlush1
Sep 12, 2016 10:45 AM CST
Kelli ...

Maybe if I explain my watering practices in my hot and dry summer climate it may help you decide how you might want to address how you might want to change how you care for your plants.

My summer temps are in the high 90s to low 100s daily for 3 to 4 months and I am gardening in rocky clay soil. I do not plant anything under the canopy of my roses and mulch heavily. That was how I was taught to care for my roses so that I don't disturb the feeder roots that take up moisture and nutrients and to avoid competition for water and food.. Other gardeners have different gardening styles.

The area under the canopy of the rose is mulched heavily to maintain a constant moisture and to reduce weeds.

I water my roses deeply once a week by placing a sprinkler under the rose that waters the area under the whole canopy of the. The amount of time depends on the the size of the rose. For the larger roses, it runs from 15 to 20 minutes per rose. For the minifloras 10 minutes, miniatures and microminis 5 minutes. Mid-week they get what I call a "feeder root" watering ... just enough to keep the top six inches of the soil moist. It runs about 10 minutes for the larger roses. The other roses just get sprayed as needed.

Sufficient watering is very important in our dry climates to keep the plants well foliated to help them through the high summer temps.

Hot and dry climates are the perfect environment for spider mite infestations which can defoliate a roses within a day, so I wash down my roses daily with a strong stream of water both on top of the leaves and on the under sides of the leaves. It only takes me about 20 minutes to go through the whole garden with the hose to wash down the roses. If I see a rose that needs a bit more water, I give it an extra shot at that time.

I am growing more than 100 roses, so I have a feel for what I am seeing and can tell when I need to give a rose a little extra water. Mountain sunlight can be pretty intense and water needs vary though out the garden.

The basic rule of thumb is that you never want the root zone to fully dry out. The rose may not be able to pull enough moisture to the top growth because the transpiration of moisture through the leaves is higher because of the heat than the plant can move moisture through the plant, but the moisture is available to the plant.

When I spoke of a rejuvenation prune, I was suggesting that younger wood is more efficient at moving moisture / sap through the plant than older wood. Just something to think about.

Good luck with your roses.

dang typos and lousy editor .. me
I'd rather weed than dust ... the weeds stay gone longer.
[Last edited by RoseBlush1 - Sep 12, 2016 11:22 AM (+)]
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Name: Sue
Ontario, Canada (Zone 4a)
Daylilies Birds Enjoys or suffers cold winters Native Plants and Wildflowers Butterflies Annuals
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sooby
Sep 12, 2016 10:58 AM CST
One thing I would add is that a soaker hose generally needs to run for a lot longer period than an overhead sprinkler because it doesn't deliver as much water per minute. Also if you have a wood mulch that gets dried out, it can absorb a lot of the irrigation water itself before any even gets through to the ground beneath (if applied from above the mulch). I found that out the hard way!
Name: Kelli
Canoga Park, CA, Sunset 19 (Zone 10a)
Where summer is winter
Region: California Celebrating Gardening: 2015
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Kelli
Sep 12, 2016 11:19 AM CST
Thank you, Lyn. I need to mulch. It is just bare ground. It always has been. We have a lot of fallen wisteria leaves that need a home.
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Name: Lyn
Weaverville, California (Zone 8a)
Garden Ideas: Level 1 Garden Sages Celebrating Gardening: 2015
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RoseBlush1
Sep 12, 2016 5:47 PM CST
Kelli ...

The schedule and timing I described in my post is what works in my climate and my soil. You will have to experiment to find out what works for you. I just wanted to show you how much water a rose needed in a hot and dry climate.

Since you live in southern California, you will probably have to water all year. I think it would be more water wise and less labor intensive, if you can afford it, to install a drip system for your roses. They will need more water during the high heat periods and it will have to be adjusted for the other seasons, but it won't be so much work for you.

Not all leaves are equal for mulch. Some mat horribly and inhibit water from reaching the soil. (Oh, and if you buy commercial compost or soil amendment, you want to avoid anything that has a lot of peat in it because if peat dries out in an arid climate, it is like concrete and will block all water from reaching the soil. I use it as a weed barrier under my rock borders. It's wonderful for that purpose .. Smiling ) Also, some leaves decompose very quickly in high heat and you are constantly having to replace your mulch. If you mix pine straw ... you often can get it at garden centers ... or even regular straw with your leaves, your leaf mulch will last longer during the summer months.

As for organics ... they are wonderful, too .... keep in mind, high temps in an arid climate use them up faster than in a more humid climate, so you need to feed the plants more often if you are using organics to feed your roses.

Good luck with your roses.

Sue ... thank you for the heads up about using wood chips for mulch. I hadn't connect those dots ... Smiling
I'd rather weed than dust ... the weeds stay gone longer.
Name: Kelli
Canoga Park, CA, Sunset 19 (Zone 10a)
Where summer is winter
Region: California Celebrating Gardening: 2015
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Kelli
Sep 13, 2016 9:00 AM CST
Thank you for the info, Lyn. We do have some pine needles mixed with the wisteria leaves. They will need to be replaced at least once a year, but the rose bed is small and we get a lot of leaves. They don't seem to mat much. We have used them in the vegetable garden. And, yes, I do water all year.
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