Hydrangeas forum: help with maintaining Hydrangea

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Oct 1, 2017 1:04 PM CST
I have had this Hydrangea for over a year now, and am looking for advice. I am in the Houston area, and it is in a large container in a mostly shaded area.

When I first planted it, most of the leaves died, leaving a fairly bare plant. Then we had a freeze over the winter which killed the rest of the leaves. The next year, it grew strong. However, the blooms that came out were lacking in color (pink/grey). Also, the plant has grown quite large (and growth is strong right now), but there are no blooms on the outside. Recently, many of the lower leaves started dying (images attached). They start to get some spots, lose some color, then fall off. Most of the leaves are showing this symptom to some extent, though not the newer ones at the top.

1. what is happening to the leaves? E.g. Is it insects? Fungus? Underwatering? Overwatering? Or simply age?
2. Any recommendations to get blooms?
3. What is the best time/way to prune to size?

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Hurst, TX (Zone 8a)
Dog Lover Region: Texas
Oct 2, 2017 12:42 PM CST
The colors that you get with mopheads and lacecap hydrangeas are influenced by the soil pH and the presence or absence of aluminum. If the soil is "solidly" alkaline then you get a shade of pink in the blooms. If the soil pH is neutral or your shrub's roots are 'mixed' -meaning, some roots are in the potting soil only & some are extending into your garden soil- then you can get a mix of colors. Near neutral, you get cases or white-ish or gray-ish colors. In future years, as the roots are mostly in your garden soil and since I assume your part of Houston has alkaline soil then you will get pink-ish colors.

In January 5-7 of this year, we had a sudden drop of temps that affected many hydrangeas and which killed many flower buds that bloom on old wood. This resulted in less blooms or no blooms. If this is a rebloomer hydrangea, you should get a second flush of blooms (say late summer or early fall).

The existing leaves in the pictures show that the shrub has Cercospora Leaf Spot, a fungal disease that becomes visible in the Fall. There is no cure; there are some fungicides that can help control the infestation but they are expensive. Since the leaves are going to dry out "soon" as winter approaches anyways, it is hard to make a case for applying these fungicides. To minimize the problem, you can try to water the shrub by watering the soil (not the leaves) early in the morning only. Do not do overheard watering if you can help it. As for the bad looking leaves, I would leave them and remove them & the blooms later when they dry out: carefully cut the petiole that links the hydrangea stems to leaves or to blooms when the plant has gone dormant; then throw away the leaves and blooms in the trash. They currently contain fungal spores and this will get rid of the source of the spores. You can also replace the mulch if the infestation is large. Increasing the air flow around the shrub can also help minimize the leaf spots at the end of Summer.

I am in the same boat as you are with that issue but my shrub is planted in the ground. It is an unnamed mophead that came with the house. I switched to water using drip irrigation when the old sprinkler system died. It always has issues this time of the year but that helps minimize the problem. This year has been very rainy here (no hurricanes here though) so the infestation has been more active than usual. If I see a particular leaf that is chuck full of these leaf spots and it bugs me bad enough, I may cut off those leaves early but otherwise I leave them until they dry out.

If the plant has gotten too much water lately, it may be responding by getting rid of some leaves. When stressed, hydrangeas sometimes get rid of leaves on the bottom and show their feet. For example, paniculatas are notorious for doing this due to summer heat stress. Potted plants may have moisture issues if they loose all their leaves. If they need more water, you should notice that the leaves edges brown out and the browning moves inwards if the problem is not corrected. A hydrangea in shady conditons can still dry out in our warm summers. For example, in the summer, we tend to have light winds from the south that dry the shrubs and require doing frequent waterings.

If the leaf veins are turning yellow, there may be a nitrogen deficiency in the potting soil. Or you may be watering too much and the roots cannot absorb nutrients well. Potted hydrangeas need frequent watering and loose minerals in the potting medium easily due to these frequent watering so make sure the soil has basic minerals by fertilizing more often than if planted on the ground. I fertilize using a slow release, general purpose fertilizer with a NPK Ratio of 10-10-10 and then I add either Liquid Seaweed or Liquid Fish to the water once a month; these products contains secondary minerals that plants need.

Pruning now is not recommended unless you do NOT want to blooms in 2018. In mid-July -more or less-, mopheads and lacecaps developed invisible flower buds that will open in Spring 2018. These invisible flower buds are located at the ends of the stems so pruning now can result in reduced or in no bloomage next year. If this shrub is a rebloomer hydrangea, new growth that develops next year may produce blooms in the Summer/Fall. So if you want blooms, better prune instead after the shrubs have bloomed in Spring but before the end of June. If you do not care about blooms in 2018 then the best time to prune would be when the shrub is dormant as its leaves have dried and maybe fallen (which makes the stems/branches more visible).

Altogether, the shrub looks fine and is even producing new leaves per the photos. Because my soil is alkaline up here, I amend the soil in the Spring & Fall to reduce yellowing of leaves (leaves yellow out but the leaf veins remain green). You can use garden sulfur, aluminum sulfate or iron-chelated liquids sold at many plant nurseries.

To produce good bloomage, make sure that the plant gets morning sun (until about 11am, more or less) in the summer or in dappled sun. Definitely no afternoon or evening summer sun here in Texas. Dense shade might affect flower production but dappled sun is ok. Full shade in bright light conditions is also ok. A few hours of morning sun is also fine.

[Last edited by luis_pr - Oct 3, 2017 1:47 AM (+)]
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Oct 26, 2017 10:54 AM CST
This is excellent information. Very clear and thorough, thank you. It's reassuring to know what the cause is, and that there's not too much that can be done.

It was advertised as "Endless Summer" so I assume it is a rebloomer.

Re: Removing Leaves
If I remove a leaf that is heavily diseased and/or almost dry, is it ok to just "snap" it off where the leaf connects to the stem, or should I always cut the petiole to leave something connected to the stem?

About pruning:
You are saying that the buds are at the end of stems, which is why you don't want to shorten a stem outside of the narrow window you mentioned (assuming you want blooms next year). What about specific stems that you don't care about? You mentioned increasing air flow, so perhaps I should cut out (or back) some stems to make it less cluttered, or even some stems that appear to be dead at the bottom.

Or perhaps is it advisable to keep a network of branches at the bottom for support?

Hurst, TX (Zone 8a)
Dog Lover Region: Texas
Oct 27, 2017 6:19 AM CST
You can just cut the petiole that connects the leaf and the stem to play it safe. I sometimes snap leaves too (other shrubs) and end up cutting parts of branches that I did not mean to cut. :o(

The endings of the stems contain -right now- invisible flower buds that will open in the Spring. Assume the flower buds are near the ends: "emergency" or back up flower buds (my words) are also located in that general area in case they are ever needed. So, you just need to be careful not to cut off the ends of the stems if you want flowers there. Then throw the infected leaf/stems in the trash (not in the compost pile as the leaf contains fungal spores that you do not want to spread).

Feel free to completely prune stems that you do not care about. Hint: as soon as the shrubs go dormant and the leaves dry out, you will be able to see what the "inside" looks like so prune live stems then. You can prune those stems aread dead right now; be careful if you delay cutting dead wood though, all the stems may all look dead once the plant hardens for winter. I would cut any dead wood now since I can tell them apart easily now.

If you see any live stems that you want to prune, wait until the shrub has gone dormant. That is because pruning can sometimes trigger new growth and you do not want new growth at this time of the year. :o) Tonite's low is 35 up here by the way!

Improved air flow can be attained as you suggest or you can simply keep other plants a distance away, not touching.

I try not to keep dead wood at the bottom (I cut 1" from the bottom or so) although the crown is at the bottom and there will be sticks that remain in that zone. Eventually they disintegrate though.... Generally speaking, it is recommended to prune dead wood to prevent fungal issues, diseases and other issues. Spores can accumulate there; insects can hide; etc. That kind of a thing.
[Last edited by luis_pr - Oct 27, 2017 7:38 AM (+)]
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Nov 9, 2017 8:46 AM CST
Thank you!

May 19, 2018 5:16 PM CST
Anyone know what's happening to my hydrangea? Kinda new to them and just wanted to know if I can save it. It's a nikko blue.
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Hurst, TX (Zone 8a)
Dog Lover Region: Texas
May 20, 2018 2:11 AM CST
Hello, znace. Four observations/comments...

* About the wilting... it is normal with new ones and in hot/windy times; one of mine looked even sadder 2-3 days ago. ;o) Newly planted hydrangeas are very sensitive to sun/heat and being "thrown/planted outside" takes a while to get used to. It is called transplant shock. Their root system has been cut to fit into plastic pots, which causes the shrubs to need extra care and watering on their first 1-3 years. As temperatures above 85 approach, the leaves will loose moisture faster than their limited root system can absorb so the plant develops wilting episodes; these episodes will be reduced once the shrub becomes established (the roots are larger). Typically though, these wilting episodes will be over by the next morning... usually with no action from you as long as the soil is kept as evenly moist -not wet- as you can make it.

If I see a wilting episode that looks extreme, I immediately water the soil from the root ball outwards (give it 1/2 to 1 gallon of water). If it is not an extreme episode, test the soil by inserting a finger into the ground to see if it feels dry and water (1/2 to 1 gallon of water) if it feels dry. If the soil is moist or wet, the plant should correct itself on its own by the next morning.

Wilting happens too when it is windy, in which case I try to water the night before I hear of wind advisories.

Another thing I have also done to some small & new hydrangeas is to block the wind if the location is windy; temporarily (during the summer) cover them with a outside umbrella or chair until it becomes used to the summer sun. If I see too many of these wilting episodes, I may just put a chair to cover the shrub regardless of time of the year. Use 1/2 to 1 gallon of water every time that you water; tweak that with the aim of getting the top 8" of soil wet.

* About something that is not clear on the picture... Some of the leaves show a discoloration and am not sure what color it really is. Made me think of sunscorch, weather/minerals issues and powdery mildew...

To prevent sunscorch, make sure that the plant is getting afternoon and evening shade. They will bloom fine in morning sun only until 11am-ish. I have some with 2 hrs of direct morning sun and they bloom fine too. If the leaves get sunscorch, the leaves in direct contact with the sun turn yellow or off-white (including the leaf veins) but the leaves underneath will remain dark green.

Some leaves also turn a purplish color when they leaf out in Spring due to weather or mineral issues but this is usually temporary.

Also, a grayish/whiteish color on the leaves can indicate that the plant nursery was watering the leaves and the shrub developed some powdery mildew. I dilute some milk in water and spray it to the leaves weekly (or more often) when that happens; a ratio 1 cup milk to 9 cups of water (alternative ratios: 2 to 8 or 3 to 7) is a good starting place.

* About mulch.... they need 2-4" of organic mulch up to the drip line.... further if you are in hot or windy locations. I do not recommend rocks as mulch near hydrangeas. Mulch makes the water in your watering last longer and makes the roots happier in hot summers and cold winters. Right now, on the upper right side of the picture at least, the soil in the picture looks dry. Use the finger method to help with that; see below.

How to control under and over watering... Insert a finger into the soil to a depth of 4" early in the early morning to see if the soil feels dry, moist or wet. Do this for 2-3 weeks daily, more or less at the same time. When the soil feels dry or almost dry then water (say, 1 gallon of water) and make a note that you watered on a wall calendar. After 2-3 weeks, review your calendar notes and determine about how often you were watering (every 3 days? 4 days? etc). Then water manually or set the drip irrigation or the sprinkler to water 1 gallon on the same frequency (every 3 days? every 4 days? etc).

Never water the leaves if you can help it. This prevents fungal infections. When manually watering, start near the crown or root ball and water outwards in all directions. Remember that right now, the roots extend as long as the plastic pot used to be width-wise.

Repeat the finger method if your temperatures go up or down by 10-15 degrees and stay there. Expect to be watering more per watering or more often in the summer months. Expect to need less water per watering or fewer waterings per week in the Fall. In the winter, if your soil does not freeze, you need to water in dry sinters but, once a week or once every two weeks should be enough.

* About Nikko Blue... you did not say where you are located and your USDA Zone. Your NB already shows one bloom in your picture so congrats! That is like two that I have but mine are still small; smaller than yours; but each one has one bloom too. This type of mophead develops invisible flower buds here in mid July ish (varies from year to year) but they can develop the flower buds in August-September further north. Thus, try not to prune the ends of the stems after the end of June. Not that they need pruning. I have never pruned hydrangeas because they are too large (NB gets about 6' or more in some places) although I allow for the larger size when planting if given size ranges in the plant label. In areas with short growing seasons, select the smaller size estimate in the plant label. The only pruning I do is when they have stems that do not leaf out by the end of May.

The invisible flower buds develop near the ends of the stems; they stay hidden thru winter and open in Spring. What you see now in the pic is called the broccoli phase of the blooms... this is the time when the buds start to open. In cold locations, you may need to protect these invisible flower buds from bitter cold winter by putting chicken wire around the bush in the Fall and filling the inside with mulch or pack it full of leaves. Top with cardboard & rocks to prevent the leaves from flying away. Add more if settling occurs by mid winter. NB blooms will be a shade of blue in your garden soil if your soil is acidic, purple-ish in slightly acidic soil and a shade of pink in alkaline soils.

If you feel you must move the shrub because it gets too much sun, etc, join the club. You can do that at any time but I try to do that before summer rears its ugly head.

[Last edited by luis_pr - May 21, 2018 1:42 AM (+)]
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