Ask a Question forum: Oak leaf hydrangeas

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Lorne Victoria
SueEverett
Dec 7, 2017 4:51 PM CST
Hello garden sages

Could you please suggest why my oakleaf hydrangeas have not flowered for the last 3 years. They flowered a few years ago and are situated in a shady position that gets some afternoon sun next to some conventional hydrangeas that flower beautifully.

Thank you
Sue
Name: Daisy I
Reno, Nv (Zone 6b)
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DaisyI
Dec 7, 2017 6:33 PM CST
Welcome!

Two thoughts:

Do you prune AFTER flowering? They bloom on old wood so winter or spring pruning with cut off the future flowers.

Has something changed that the plant no longer gets enough sun to flower?

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Lorne Victoria
SueEverett
Dec 7, 2017 7:05 PM CST
Dear Daisyl

Thank you for your speedy response. I'm thinking it may not get enough sun but the conventional hydrangeas flower. I do prune at the end of autumn.

Regards
Sue
Name: Sue
Ontario, Canada (Zone 4a)
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sooby
Dec 8, 2017 11:57 AM CST
Welcome! How are you pruning it? Is it just taking out dead stems or do you cut back living stems? If the latter and it is too late in the year, then you are cutting off the following year's flowers.
Hurst, TX (Zone 8a)
luis_pr
Dec 8, 2017 6:45 PM CST
Hello, Sue. I agree, you should not prune it at the end of autumn.

Hydrangeas that bloom on old wood (such as mopheads, lacecaps, oakleafs, serratas, asperas, etc), they all develop invisible flower buds in July-August. These buds then open in Spring so, your plant is basically producing flower buds in the Fall for Spring but you are cutting them off.

The invisible flower buds are usually located at the ends of the stems. Here is a picture of a flower bud that has opened at the end of an oakleaf hydrangea stem:

http://thewelldressedgarden.co...

Under normal conditions, if a hydrangea is planted where it can attain its advertised size, it should not need to be pruned. At the end of May, however, you can prune any stems that have not leafed out by then.

Another alternative time to prune is to prune after blooming (so you can enjoy the bloomage) but before the end of June.

Alice, Snow Queen, Snowflake, Harmony and others get very tall, 8 to 10 feet (2.5 to 3 meters). Ruby Slippers, Munchkin, Sikes Dwarf, Pee Wee get about 6' or less (1.8 meters).

I have a Snow Queen planted under a Crape Myrtle and besides a tall holly; SQ gets a little dappled sun around noon and it blooms reliably. A Pee Wee that I have planted under a holly gets less direct sun but it too blooms reliably. Note that both of them get a lot of indirect sun so it is not like they are in dense shade. Oakleaf hydrangeas prefer dappled sun or morning sun/afternoon shade.

The more sun that they get, the better of a "leaf color show" they will put in the Fall. Leaves in the Fall normally turn orange-ish, reddish and or purplish... if they get enough sun and weather conditions are favorable (warm temps are not considered "favorable"). Oakleafs should be winter hardy to Zone 5.

http://www.louistheplantgeek.c...

To prepare them for winter, just make sure they have mulch up to the drip line (more if your winters are harsh or your summers are very hot). If you see temps about to crash from above freezing to well below freezing, it may help to water them the night before (if your soil does not freeze). If the soil does not freeze, water them once every two weeks when winters are dry. We are expecting a La Nin~a Weather Event and that means dry winters in my area.

As far as watering goes at other times, you can insert a finger to a depth of 4 inches (10cm) and water when the soil feels dry or almost dry. Aim to water deeply so the water reaches reaches down to about 8 inches down (20cm) every time you water. A starting point may be to water 1 gallon per water (3.8 liters). I usually start with that, increase it as summer approaches and then go back down to that level in the Fall. During winter, because my winters are mild, I water once every two weeks or so, depending if it is dry or not.

When the plant leafs out, you can apply some fertilizer. I generally use either composted manure or cottonseed meal but you can also use organic compost or a fertilizer whose NPK Ratio is around 10-10-10 like some versions of Osmocote. When selecting chemical fertilizers, use fertilizers that are slow-release, general purpose. One application in Spring only (plus mulch) should be enough for the whole year. I usually use about 1/2 to 1 cup of composted manure or cottonseed meal per plant but feel free to use more on a hydrangea that happens to be very large. Too much fertilizer can increase the amt of nitrogen in the soil and that could prevent blooms... another thing to consider.

In addition to the fertilizer, I also amend my alkaline soil in Spring. And also after August/September. But I think your soil may be acidic and not need to be amended.

I hope that helps?
Luis
[Last edited by luis_pr - Dec 9, 2017 8:12 PM (+)]
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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
Dec 9, 2017 5:19 AM CST
Just thought I'd mention, Luis, that Sue is in Australia which would change the timing and probably a few other things.
Hurst, TX (Zone 8a)
luis_pr
Dec 9, 2017 7:21 AM CST
Oops, I saw Victoria and thought she was talking about Victoria Island, Canada. Sorry, Sue. You are relatively closer (than me) to my sister in law; she lives in Perth.

Please tweak my month references by about 6 months.

Thanks for catching that error, Sooby.
[Last edited by luis_pr - Dec 9, 2017 1:30 PM (+)]
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Name: Sue
Ontario, Canada (Zone 4a)
Daylilies Birds Enjoys or suffers cold winters Native Plants and Wildflowers Butterflies Annuals
Region: Canadian Keeps Horses Dog Lover Plant Identifier Garden Sages
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sooby
Dec 9, 2017 8:48 AM CST
I thought Victoria BC as well initially, Luis, but then I went to check for the hardiness zone because of course it's much milder there than most of the rest of Canada, and discovered when I looked it up that Lorne is in Victoria, Australia.
Lorne Victoria
SueEverett
Dec 9, 2017 9:38 AM CST
Dear Daisyl

Thank you for your speedy response. I'm thinking it may not get enough sun but the conventional hydrangeas flower. I do prune at the end of autumn.

Regards
Sue
Hurst, TX (Zone 8a)
luis_pr
Dec 9, 2017 11:09 AM CST
Hydrangeas can flower with little amounts of dappled sun. I learned that from watching a mophead that my sister's neighbor had and which I originally thought would not bloom or would not bloom well because I typically saw it when shaded. Now I have a Pee Wee (oakleaf) under a holly tree that gives it a tiny bit of dappled sun during the 12pm hour; on the east side, the holly tree has another holly tree which blocks a lot of the sun; Pee Wee has another dense holly on its west side and a tall wooden fence on the south so sunlight can only come -indirectly- from the northern side.... yet it blooms very well too.

Have you "measured" from when to when does it get sun? Dense shade would start to produce issues. Another suggestion: post pictures of the location when it is getting sun and shade. Indirect sunlight is as good as direct sun, which is why I suspect the shrub is producing flower buds. Also, consider the possibility of having too much fertilizer that I previously mentioned.

Conventional hydrangeas like mopheads- would also not bloom if pruned in autumn, although there are some newer varieties that bloom on old and new wood. Those, if they pruned in autumn, will not bloom in early Spring but will produce blooms later from new wood.
[Last edited by luis_pr - Dec 10, 2017 3:18 AM (+)]
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Lorne Victoria
SueEverett
Dec 10, 2017 4:31 PM CST
Thank you all for your helpful responses.

Kind regards

Sue

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