Ask a Question forum: What is causing leaves to yellow and brown and drop?

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Name: Sheridragonfly/Sheri
Alabama (Zone 8b)
Salvias Celebrating Gardening: 2015
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Sheridragonfly
Aug 12, 2015 9:25 AM CST
I have 3 butterfly bushes..One did the same a month ago in July and it was
HOT and humid.. not too much water...in the soil to cause it
It dropped its leaves they turned brown and fell off...

I cut it back to 15 inches and it is now putting on tiny green leaves on that
bush Miss Ruby

Miss Molly is turning yellow and leaves brown and dropping leaves and I know
it is not too dry or over watered...it has afternoon shade but half day sun
and enough moisture..the Miss molly beside it is green and doing good
green and not dropping leaves and not yellowing..

It has been 104 heat index here for a few weeks...
temp in the 96 -99 range...but they get shaded in afternoon ...not in the burning
sun all day

the healthy Miss molly is shown here in a photo and it is 3 foot from the one that
is suffering and dropping leaves ...entire bush...

Do you know what I can do and what is causing this to happen..
Sheri
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Name: tarev
San Joaquin County, CA (Zone 9b)
Always count your blessings in life
Region: California Houseplants Plays in the sandbox Orchids Plant Lover: Loves 'em all! Composter
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tarev
Aug 13, 2015 3:18 PM CST
Hi Sheri, I do not grow butterfly bushes, but my plants exhibit similar dropping of leaves, even our city trees do it when we go into heat wave mode especially triple digits. It is the plant's reaction to the heat, they will drop the older, lower leaves and maintain only what they can sustain through the heat. If I see we have a forecast of days of high 90's to triple digits, I deep water a day ahead, so the plants can drink up and save up what it can then if heat wave continues, another deep watering mid week when it is still early in the day to help them drink some more before more baking heat ensues.

At least you got some humidity there, we have really dry dismal humidity, no rain since it is drought here, so lots and lots of falling leaves. The plants stabilize again when our temps return to the more tolerable high 70's to low 80's, I see them slowly making new leaf growths again. Smiling
Name: Sheridragonfly/Sheri
Alabama (Zone 8b)
Salvias Celebrating Gardening: 2015
Image
Sheridragonfly
Aug 13, 2015 3:35 PM CST
thank you so MUCH for answering my post!

I trimmed it back half way...and watered it well this week
and I think it will be okay ..

I would never prune back
later than mid August due to I did that one year on oct lst
and we did not have a frost or freeze till late november and it
killed my butterfly bush...

it did not have time I guess to harden
off in the stems

where I pruned it back to half the height and moved it 4 foot over
to another spot in the same flower bed...

I would have thought in zone lower 8 it would have gotten established
from moving it and pruning it on oct lst but it killed it...

I normally prune back March lst all my butterfly bushs, salvias or anything else in the flower garden
in our area..and that is the best time for us..so the plant does not go into shock...

Thanks again
Sheri
Name: tarev
San Joaquin County, CA (Zone 9b)
Always count your blessings in life
Region: California Houseplants Plays in the sandbox Orchids Plant Lover: Loves 'em all! Composter
Cactus and Succulents Dragonflies Hummingbirder Amaryllis Container Gardener Xeriscape
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tarev
Aug 13, 2015 3:44 PM CST
I do the same thing with my other bush like plants, prune in early Spring. Smiling I still get some late bloomers around Fall, so I wait for the last batch to show up.
Name: Sheridragonfly/Sheri
Alabama (Zone 8b)
Salvias Celebrating Gardening: 2015
Image
Sheridragonfly
Aug 13, 2015 4:02 PM CST
thank you
sheri
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Name: Lyn
Weaverville, California (Zone 8a)
Garden Ideas: Level 1 Garden Sages Celebrating Gardening: 2015
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RoseBlush1
Aug 13, 2015 11:31 PM CST
Sheri ....

Tarev is right on about plants abandoning growth they cannot support during high temps.

I live in a climate very similar to his, but I live further north and up in the mountains above the Valley, so there is a greater variance between my day temps and night temps. I also don't get the benefit of the Delta breezes he has mentioned in other posts.

I grow a lot of roses, which I normally prune in spring, but I do need to prune some of them a bit in fall to avoid snow breakage. My rule of thumb is not to prune a plant back until the day temps are in the 80s and are likely to stay there or go lower. This is because in many plants, certainly roses, pruning stimulates new growth which would fry when temps are in the 90s or above. This uses plant energy, so I wait.

I also don't do a hard prune in fall because my modern roses store nutrients in their canes to carry them through the winter months and into spring. My pruning is simply to open the plants up so that the snow can fall through them and so that I am the one deciding how far the plant gets pruned back rather than Mother Nature.

I, too, like getting that last flush of roses .. Smiling

I don't know your climate, but I thought I'd share a different approach to pruning.

Smiles,
Lyn
I'd rather weed than dust ... the weeds stay gone longer.
Name: Sheridragonfly/Sheri
Alabama (Zone 8b)
Salvias Celebrating Gardening: 2015
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Sheridragonfly
Aug 14, 2015 8:26 AM CST
that is true
I ought to have waited to prune the butterfly bush that was dropping leaves and brown
and left it till March lst next year

but I have pruned it and the heat is 95 today

but afternoon shade so hope it lives

it is a Miss Molly and I paid a lot of money for it..3 gallon container one this
past april...

thanks for the pruning tips..
When I had roses I always pruned last of February here which was perfect..
I understand your advice, it was easy to understand and helpful
so thank you for it..

Take care
Sheri in Alabama
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Name: Cindy
Hobart, IN zone 5
aka CindyMzone5
Celebrating Gardening: 2015 Plant Identifier
Shadegardener
Aug 14, 2015 9:08 AM CST
Up here in the north, we're used to butterfly bushes dying back to the ground over winter but regrowing in the spring. Is that different from heat stress causing die-back in the summer?
Name: Sheridragonfly/Sheri
Alabama (Zone 8b)
Salvias Celebrating Gardening: 2015
Image
Sheridragonfly
Aug 14, 2015 9:14 AM CST
yes the butterfly bushes die back here ..first freeze in november late
and then look dormant till April..they put out new green growth then
and bloom in late may ...till frost here...

Roses would do the same ...and all perennials...
here..

Watching the hummingbirds we only get the Ruby Red Throat
and I have about 12 now...and that is a lot...
I expect in sept there will be 50 of them flying from the northern usa
above me through here and then on down to central america or
lower Florida to winter there...

I am having to buy lots of white sugar and making fresh sugar water every 3 days so it will not sour
in the heat outside and also they are increasing drinking now to put weight on themselves..

Sheri Thumbs up
Name: tarev
San Joaquin County, CA (Zone 9b)
Always count your blessings in life
Region: California Houseplants Plays in the sandbox Orchids Plant Lover: Loves 'em all! Composter
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tarev
Aug 14, 2015 9:16 AM CST
Exactly what it is, heat stress.
Name: Lyn
Weaverville, California (Zone 8a)
Garden Ideas: Level 1 Garden Sages Celebrating Gardening: 2015
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RoseBlush1
Aug 14, 2015 12:07 PM CST
Tarev ....

Heat stress occurs when the transpiration rate (loss of moisture) from the leaves is greater than when the plant can pull moisture up from the roots to support the top growth.

A plant can have sufficient water in the root zone to survive, but it can only pull moisture up as fast as the plant is genetically programmed to perform that function. However, there's another rule of thumb ...
on many shrub type plants, the older wood is less efficient than new wood.

You can mitigate the higher transpiration rate a bit by planting where the plant can get some shade during part of the day so that it is not cooking in high heat all day.

I use roses for my example because I understand the botany of the plants, have grown them in several climates and have a broad knowledge of the different classes and cultivars. What is true for roses is not necessarily true for all plants. The concept of transpiration rate is one of the things that is true for all plants that I know of at this time.

With roses (not all roses), you can also make the plant more heat tolerant by using the cultural practice of doing a rejuvenation prune when you are doing your spring pruning. The general practice is to take out one or two old canes at the base of the plant .... note I am talking about modern, repeat blooming roses for the most part. By following this practice, you are stimulating new growth from the base of the plant and over time you virtually end up with a plant with wood .... main canes ... that is of varying ages and efficiency and generally you end up with a healthier and more heat tolerant plant. With more efficient wood, the plant can pull up moisture better than if it only has old wood.

Some plants are simply not heat tolerant at all and no matter what you do, they cannot be grown well in climates with high heat.

There's a more to it, but this is your basic answer.

Smiles,
Lyn
I'd rather weed than dust ... the weeds stay gone longer.
Name: Sheridragonfly/Sheri
Alabama (Zone 8b)
Salvias Celebrating Gardening: 2015
Image
Sheridragonfly
Aug 14, 2015 12:15 PM CST
that is how I used to do my hybrid tea rose garden.
Good information that many can use that you provided.

I would not plant anything in my area in all day full sun..

Thank goodness I had one area that gets morning sun
till 2 pm and then is shady in most areas..dappled sunlight.

That is where my flower bed is located ..huge trees behind
it....but not over it...

on a hillside..

House on one side, woods on the back side of the large
Sheri's healing flower garden area...
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Name: Lyn
Weaverville, California (Zone 8a)
Garden Ideas: Level 1 Garden Sages Celebrating Gardening: 2015
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RoseBlush1
Aug 14, 2015 12:25 PM CST
Your flower bed is lovely, Sheri.

Heat is only one of the variables. The quality of the direct sunlight can make a difference, the soil and more.

I don't have any shade in my gardening areas, so I had to select roses ... yes, I am an addict ... that could do well is less than ideal conditions. Some of my roses will go summer dormant, but not many. Some can still bloom and not fry in high heat, while others are only beautiful in spring and fall.

Smiles,
Lyn
I'd rather weed than dust ... the weeds stay gone longer.
Name: tarev
San Joaquin County, CA (Zone 9b)
Always count your blessings in life
Region: California Houseplants Plays in the sandbox Orchids Plant Lover: Loves 'em all! Composter
Cactus and Succulents Dragonflies Hummingbirder Amaryllis Container Gardener Xeriscape
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tarev
Aug 14, 2015 12:32 PM CST
So true Lyn, and that is why living in our area with baking hot days always in summer, I have learned to plant those that are not too water needy. Have more on succulents and drought tolerant plants. I just enjoy the plants elsewhere when I see them nearer to Bay area where temps are more cordial to the plants. But I do have some orchids, which I just have to choose which ones are temperate enough to survive here...but whatever type of plant we have...anytime it goes beyond 95F..it is just a survival of the toughest. We can only do as much mulching or watering.

I used to lament that my garden gets too shaded in summer, I realize now, that shade is the only thing that is really helping my plants endure the heat we have. So now I am okay with it. Then I see that I still manage to get late blooms in Fall, so one last chance to enjoy some of my bloomers, before they rest again in winter. Our friendly city trees, love their shade in summer, though we get a lot of leaf drop when it really gets hot..and then cold weather dormancy ...more leaf drop..oh well..just the way they grow, so got to live with it.

There is one plant I tried this year - Caladiums- prize I got in our raffle here in ATP, which I thought initially will not like it since our humidity here is too poor...and surprisingly it is really doing well in this heat as long as I keep it moist. True heat lovers they are..as long as they have a good drink Smiling Amazing big leaves! I think I will repeat them again next year. Big Grin
Name: Lyn
Weaverville, California (Zone 8a)
Garden Ideas: Level 1 Garden Sages Celebrating Gardening: 2015
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RoseBlush1
Aug 14, 2015 12:47 PM CST
tarev .......

You might want to visit the Sacramento Cemetery Rose gardens ... especially for the spring celebration ... to see roses that are doing very well in a hot, dry climate. I am more familiar with the old rose garden which consists of roses found all over the gold country on old homesteads and cemeteries to see if you might find something that you might like to grow. I know they have a modern rose garden there, too.

You can visit a couple of times a year and see how the plants are doing in the heat.

There are a lot of roses that are more shade tolerant than the hybrid tea class.

I haven't found a spot in my garden where succulants can thrive because I don't have enough shade.

Smiles,
Lyn
I'd rather weed than dust ... the weeds stay gone longer.
Name: tarev
San Joaquin County, CA (Zone 9b)
Always count your blessings in life
Region: California Houseplants Plays in the sandbox Orchids Plant Lover: Loves 'em all! Composter
Cactus and Succulents Dragonflies Hummingbirder Amaryllis Container Gardener Xeriscape
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tarev
Aug 14, 2015 1:14 PM CST
That would be nice to see, I will look it up next spring. I like to see roses, but not much into it, just going to admire them from a nice distance. Big Grin I also visit Filoli estate gardens in Woodside, CA, that is where I really enjoy the roses very much!
Name: Sheridragonfly/Sheri
Alabama (Zone 8b)
Salvias Celebrating Gardening: 2015
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Sheridragonfly
Aug 14, 2015 3:14 PM CST
I have never been able to have succulents here nor
even yarrow which is not one but a perennial
I like them...though..
I think it is to humid here and the soil is not that rocky
sandy type that maybe those plants prefer..
you think so?

Sheri
Name: tarev
San Joaquin County, CA (Zone 9b)
Always count your blessings in life
Region: California Houseplants Plays in the sandbox Orchids Plant Lover: Loves 'em all! Composter
Cactus and Succulents Dragonflies Hummingbirder Amaryllis Container Gardener Xeriscape
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tarev
Aug 14, 2015 4:25 PM CST
I think you can, Sheri, I have known succulent growers in much more humid areas that grow them. but they do have to grow them in containers and make the media very porous, so the roots will dry out faster and be able to move them to protected space if it rains too much. Succulent tropicals like epiphyllums, plumerias, adeniums should do nicely in your area as long as in very well draining media. Just maybe steer away from the desert type succulents, those ones really want to be very dry, and in low humidity. Some succulents are dormant in summer, and some are more actively growing when temps are cooler.

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