Hydrangea Help

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Oldschool
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Hydrangea Help

Post by Oldschool » August 31st, 2019, 1:49 pm

Greetings ATY’rs...

Hoping to get some help with my hydrangeas, I believe they are the mophead variety. Located in Northwest Montana zone 5b. This is my third season and I have yet to see a bloom. I know they are capable of blooming because I’ve seen pictures of them from the prior owner.

I get annual soil test from lawn but not the hydrangea planter. Soil test from lawn shows 8.2 ph. Plants receive morning sun and brief afternoon sun. I apply Milorganite monthly from May to September. Watering is done by drip system.

I have read too many conflicting strategies on hydrangeas and just not sure what to do. If anyone has some knowledge and or experience, please share.

Thanks

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Oldschool
Posts: 235
Joined: July 2nd, 2017, 11:28 am
Location: Kalispell, Montana
Grass Type: Kentucky Bluegrass
Lawn Size: 10000-20000
Level: Some Experience

Re: Hydrangea Help

Post by Oldschool » August 31st, 2019, 2:08 pm

Just saw an older thread on same subject. I’ll read through it now...

bpgreen
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Re: Hydrangea Help

Post by bpgreen » August 31st, 2019, 10:06 pm

I don't know a lot about hydrangeas, but I think I've read that they like acidic soil. Most soil in the intermountain west is alkaline, as the soil test showed the soil in your lawn is.

It's possible that the prior owner treated the soil to make it more acidic. I think I see some signs of chlorosis in some of the leaves in those pictures. Can you verify for me that some leaves are somewhat yellow with green leaves? If so, that's a sign that the plant is iron deprived. There's usually plenty of iron in the soil in the intermountain west, but plants can't use it due to the high ph.

The are fertilizers that are supposed to help "avoid loving" plants. Some don't necessarily need to change the soil, but they're waterr soluble and you apply them directly to the leaves.

You can top dress with compost. That won't acidify the school, but can help make it a little better at making the nutrients available to plants.

If you can get soil sulfur, you can dig holes near the plants and bury some sulfur in them. It takes time for that to take effect, but the results can last for a fairly long time. It doesn't work to just spread the sulfur on the surface. It needs to be buried.

Oldschool
Posts: 235
Joined: July 2nd, 2017, 11:28 am
Location: Kalispell, Montana
Grass Type: Kentucky Bluegrass
Lawn Size: 10000-20000
Level: Some Experience

Re: Hydrangea Help

Post by Oldschool » August 31st, 2019, 10:55 pm

Bpgreen...thanks for the response. Yes, I confirm the yellow and green leaves. If it’s iron deficiency, I can up the ante on the Milorganite next season. The sulfur idea seems to be a popular one. I’m going to work some sulfur into the soil tomorrow. Too late in the season for results this year, cross my fingers for spring blooms.

bpgreen
Posts: 3556
Joined: January 3rd, 2009, 2:28 am
Location: Utah (Wasatch Front)
Grass Type: Western, Streambank, Crested wheatgrass in front (with blue grama added in the heckstrips), sheep fescue in back; strawberry clovetr in both
Lawn Size: 3000-5000
Level: Experienced

Re: Hydrangea Help

Post by bpgreen » August 31st, 2019, 11:43 pm

In case I want clear earlier, there's an iron deficiency, but it's not due to a lack of iron. Your soul probably had plenty of iron. The problem is that the hydrangeas can't use the iron.

Working some sulfur into the soil now is a good plan. It takes months for it to start to work. And it needs water as well, so this is perfect timing. I'd probably add some in the spring as well.

Unfortunately, this will probably be something you'll need to do on a regular basis.


TimmyG
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Re: Hydrangea Help

Post by TimmyG » September 1st, 2019, 11:06 am

Since you don't know what cultivar(s) they are, we have to assume that they are not rebloomers. In other words, they only bloom on old wood. I'm in zone 5b/6a and know firsthand how unlikely it is for a standard Hydrangea macrophylla (mophead or big-leaf hydrangea) to bloom. Following a standard winter here, the plant dies fully to ground, killing the buds that formed the previous fall. I've got at least eight mature mophead hydrangeas both in shade and full sun from the original owners and have only seen a couple blooms in the five years since we moved here, and that include the really mild winter we just had. I keep them only because the foliage has been so outstanding. Standard mophead hydrangeas just aren't a good choice for anything north of 6b/7a if you want blooms.

Fortunately, there are now a vast array of reblooming mophead hydrangeas that bloom both on old wood and new wood. You won't get the dominant flush of blooms earlier in the year on the old wood, but you can still get blooms on the new wood later in the year. The majority of newer introductions are rebloomers and far better choices for you than what you have in the ground now.

I have collected in the last couple years more than a couple dozen different cultivars of Hydrangea macrophylla and Hydrangea serrata (mountain hydrangea) that should all be good bloomers for me in zone 5b/6a. I mostly started with starter plants (tiny, mail order), so most are too small to assess blooming performance yet, but with the mild winter we just had, just about every one of them bloomed to some degree. If you can find them, I highly recommend the Tuff Stuff series of Hydrangea serrata.

But who knows. Maybe those are something like the de facto Endless Summer reblooming hydrangeas, and you have something else keeping them from blooming. I personally would go with the theory that the past owners took pictures after a very mild winter.

Oldschool
Posts: 235
Joined: July 2nd, 2017, 11:28 am
Location: Kalispell, Montana
Grass Type: Kentucky Bluegrass
Lawn Size: 10000-20000
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Re: Hydrangea Help

Post by Oldschool » September 1st, 2019, 12:08 pm

Bpgreen,

I understood what you meant about the iron deficiency. I have the same issue with my grass. Plenty of iron but unable to uptake because of the alkalinity of the soil. But the iron in Milorganite works well on the lawn. So I assumed it would have the same effect on the hydrangeas.

TimmyG
Posts: 2244
Joined: May 15th, 2012, 6:04 pm
Location: Dracut, MA
Grass Type: Northern Mix
Lawn Size: 20000-1 acre
Level: Experienced

Re: Hydrangea Help

Post by TimmyG » September 1st, 2019, 10:31 pm

Run with the iron inaccessibility theory if you must, but I don't see iron deficiency necessarily impacting blooming.

https://www.gardenmyths.com/hydrangea-myths/

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