jkhicks72
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Joined: Mon Jun 13, 2016 9:23 pm

Hydrangea with Other plants

Hello All!

I recently bought a house with a pre existing flower bed. It has pink hydrangeas, ferns, and tons of cannas plants. When I bought the house, a friend said hydrangea were hard to keep alive because they needed a certain pH balance in the soil. So, wanting to make sure I don't kill anything, I started an internet search on maintaining them. The sites said they need a alkaline soil but when I researched growing healthy cannas plants they said no no no. Does anyone have any advice about how to keep all of these plants healthy together? I also have mondo grass as the border around the beds. Advice on watering, pH levels, pruning, would all be helpful. It is a very shady area and only gets a bit of morning sun. I live in central Texas as well. Thanks in advance!

luis_pr
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Posts: 824
Joined: Sun Jul 05, 2009 8:31 am
Location: Hurst, TX USA Zone 7b/8a

Good morning, jkhicks72. Well the story is not quite like that. Hydrangeas in their native soils are understory bushes that prefer acidic locations. Using the soil pH scale, they like levels around 5. But... they do not plop and just die if their soil is alkaline. They actually tolerate some alkalinity and will do just fine if you amend the soil once or twice thru the year. How much depends on just how alkaline your soil is.

The soil where I am in north-central Texas, has alkalinity ratings around higher than a 7 (7=neutral). Your local nurseries can help you determine how much your soil is. The nurseries help some cheapo kits to help test if your soil is acid or alkaline; some people use these to tell (ahead of time) if their already amended soil is now turning alkaline). If their soil is returning back to alkaline levels then they amend again even before the hydrangea leaves show signs if iron chlorosis. I generally follow this approach: amend the soil in Spring before they leaf out and then once again in June if I notice that the leaves are showing signs of iron chlorosis. If that happens, it occurs in July-September.

You can tell when this happens because, at first the leaves tend to look light green or a little yellowish. That is a sign that they are unable to absorb iron from the soil. As the problem progresses, the leaves turn more yellowish or white-ish BUT, the leaf veins remain dark green. Here is information on the subject and a picture.

Most plant nurseries sell various types of soil amendments with sulphur that you can use to lower your soil's pH number. The products come in liquid form or powdery/etc forms. The liquids are called iron-chelated compounds and work faster than the non-liquids but they still require waiting a while so expect no overnight corrections, maybe in a week +. The other sulfur products are things like garden Sulfur, aluminum sulfate, iron sulfate and greensand. Apply the products based on the label instructions. Then make notes in a wall calendar of when did you apply them so get a feel for how often to apply them. Next time should be around Jul-Sept -maybe- or when you notice signs of iron chlorosis. Like I said, I spread whichever of the products I happen to have on hand from the base of the hydrangea outwards, maybe 1 foot past the drip line?? You do not have to be exact. I simply assume the roots will be growing into that area at some point so I sprinkle some of the stuff there. Do not control iron chlorosis with fertilizers for acidic plants because they do not have as much a kick as your soil needs.

Note though, that sometimes you get iron chlorosis signs for other reasons. In the Fall, I have gotten false positives when the rainy season starts and the plant cannot uptake much iron from the soil because of the soil is saturated with water; yes, I too have clay soil. If I notice that the signs of iron chlorosis are getting worse then I amend the soil again. But sometimes it is a small amt of iron chlorosis and if it goes away on its own, I take no action.

The non-liquid products should be used with some care. They contain sulfur and, in large enough amounts, that can hurt the roots so try not going overboard with these amendments. Of the ones listed, aluminum sulfate is toxic -in large qtys- to azaleas/rhododendrons so apply that amendments only to the hydrangeas (just to play it safe). But like I said, I just use whatever I happen to have of all the ones listed.

These products can also cause pink mopheads and lacecaps to change to shades of purple or blue. Our soil contains naturally occurring levels of aluminum and when the soil pH is lowered, the roots can absorb aluminum and the flower sometimes respond by turning lighter shade of pink or shades of purple or even blue (but you have to be well below soil pH of 7 for blues to show up) and some hydrangeas will actually resist doing the blues and get stuck in purplish colors...

Last hint... you need to do this with some regular frequency "forever" because the soil has a tendency to return to its previous alkaline levels if you do not amend the soil regularly with these amendments. Since our soils do not freeze, I sometimes apply the amendments during winter (in amounts per the label directions).

Enjoy the new house!

jkhicks72
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Posts: 9
Joined: Mon Jun 13, 2016 9:23 pm

Wow. That is a ton of information and thank you! I didn't see a picture attached? I am going to attach two of my own of the plants. We have a ton of rain here recently so I am wondering if that is a contributing factor. Also, will adding sulfer to amend the soil harm/effect any of the other plants surrounding the hydrangeas?

Thanks in advance!
Attachments
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luis_pr
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Posts: 824
Joined: Sun Jul 05, 2009 8:31 am
Location: Hurst, TX USA Zone 7b/8a

Well, I am not sure what to say. I grow some canna lilies in my alkaline soil and they have not had issues. The cannas are not located near the hydrangeas so they get lots more sun and their soil does not get amended. Only fertilized.

Very few plants will complain about the added sulfur and many just tolerate them Lilacs love alkaline soil but I have had lilacs near azaleas and that has not been a problem.

Do understand that I am basically saying to amend the soil around the hydrangeas only. You can stop after the drip line or a little after the drip line. So, you do not need to amend a plant a foot away for example.

And yes, water could be triggering iron chlorosis. I have that happen in the Fall and I wait a week or so to see if it stabilizes or is getting better on its own. If it seems to be getting yellower then I amend the soil.



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