"Hydrangea blues"

My Hydrangea plants are going to be pruned sooner rather than later this year.
Sunday, 10 February 2013     

Burnt Hydrangea flowers

After such a horribly hot summer, many of my Hydrangea bushes are looking very much the worse for wear. The flower heads were severely burned in the 45-degree day of 18 January. I usually don't prune my Hydrangea until winter but this year I am thinking of pruning this month, to tidy them up. I usually like to leave on the old flower heads to enjoy the antique shades of purple, green, russet and bronze as they age but this year the predominant colour is brown - not a good look! To prune, I remove spindly stems and cut the stems back to the lowest pair of plump buds. A couple of very gnarled old stems can be removed at ground level each year on older shrubs. Most of my shrubs are the old-fashioned 'hortensia' (macrophylla) types: tall, robust plants with thick stems, many of which I have grown from cuttings given to me over the years.

However, I have had a few smaller-growing types with much thinner stems, and I have usually pruned these in July with my other bigger ones. They have never flowered very profusely. Last year I attended an interesting presentation on Hydrangea from Mark Adamson from Heritage Plants and learned that these smaller-growing ones should be pruned in February, cutting the whole plant back by half, otherwise they don't have sufficient time to regrow flowering wood for the following late spring blooming. This was a complete revelation to me, so I will be definitely always pruning these smaller ones that way now. These include Hydrangea serrata cultivars such as 'Blue Deckle' and 'Grayswood', which I have always assumed are not great doers in Sydney. I am hoping the new pruning method will bring me more flowers next spring.

In recent times there have been some new releases of smaller-growing Hydrangea macrophylla, including the 'Endless Summer' collection, which has mophead and lacecap forms in white and pink/blue colours in various shades. I recently acquired a lacecap one (named 'Twist-n-Shout') and it has flowered very well in a pot - it can be pruned back several times to get a new flush of blooms. Another recent acquisition of these more compact ones was Hydrangea macrophylla 'You & Me', which grows about 80 cm tall and has lovely double blue flowers, also growing in a pot. These have now aged to a gorgeous greeny-pink hue (as it was in a much more protected position than the ones I have in the garden so wasn't burned), which I am enjoying. I plan to cut these back in late February to make sure they flower well next year. The tall, old-fashioned lacecap varieties are pruned more lightly in February too, as the flower heads don't ever age attractively like the mopheads. Cut them back just above the topmost pair of buds. The shrubs can be fed after pruning to encourage the new growth and fed in late winter as well.

Hydrangea flowers vary from pink to blue depending on the pH of the soil - an acid soil results in blue flowers, whilst an alkaline soil gives pink blooms. White forms are stable, though the 'eye' of the flowers may be tinged blue or pink depending on the soil. There are red ones available - I'm not sure how these fare in different soils. The colour intensity of a particular Hydrangea cultivar - whether a pale or strong colour - seems not to vary with pH, according to some growers. Various substances are available from nurseries to manipulate the colours - such as alum for blue flowers and lime for pink ones. The presence of phosphorous in the soil is also apparently a factor, so adding superphosphate will promote pinker blooms: for blue flowers you can use a plant food designed for native plants, which is low in phosphorous. These substances may take about a year to take effect, however!

Hydrangeas planted in the ground should be given good, compost-enriched soil and be kept well mulched. Hydrated cocopeat can be added to the planting soil to help retain moisture. Once they are established, they need less watering. It is best not to plant them too near to large trees with greedy roots - they grow best in the shade cast by buildings where there is no root competition. They don't mind having some morning sun - and in fact will flower better for it; it is the hot afternoon sun that will singe their leaves and burn their blooms. I obviously need to move some of my specimens!

 Reader Comments

1/14  Bob - 2076 (Zone:10 - Warm Temperate) Monday, 11 February 2013

Dear Deidre, I have always had trouble pruning my hydrangeas,everybody has a different time to do so!!!!!! I will add your latest hydrangea pruning tips to mine and act on them this week be prepared for further news, about spring next year!!!! It is certainly very confusing. I hope this works! Deirdre

2/14  Bev - 2070 (Zone:10 - Warm Temperate) Monday, 11 February 2013

Thanks Deidre - I"ll take your advice especially for my recently acquired You & Me.I have never had much luck with Grayswood but wouldn"t mind trying it again. Bluebird was also a failure but the plant I bought as Blue Deckle years ago is about the best Hydrangea in my garden - it flowers almost constantly & has even flowered again now after that hot day. I cut off dead heads & it flowers again. In winter I prune lower & cut some old stems to ground. It"s about 1.5 x 1.5 metres & growing in sun. Great to hear your Blue Deckle grows well. It is such a beautiful plant. I am interested in general as to how well the serrata ones can do in Sydney. Thanks for your feedback. Deirdre

3/14  Chris - 3340 (Zone:10 - Warm Temperate) Monday, 11 February 2013

My Hydrangeas were pretty burnt & not too attractive so I pruned them a week or so ago but not as far as your suggestion, maybe 1/3. Should I go and take more off? Thanks Chris We were told half off for the thin-stemmed ones - I think the big thick-stemmed ones can take a pretty hard pruning but maybe just see how it goes with the 1/3 off this time. Deirdre

4/14  Peta - 2758 (Zone:9 - Cool Temperate) Monday, 11 February 2013

As I grow older (and more experienced), I realise how fabulous Hydrangeas are. My neighbour grows them as cut flowers for the Sydney markets and another close by friend has the National Collection. Your advice about pruning the smaller varieties is great and makes a lot of sense - will do. I love all Hydrangeas, special favourites are H. paniculata "White Moth", H. quercifolia "Snowflake" and my miffy H. macrophylla "Quadricolor" which is a pain to propagate but has gorgeous variegated leaves. Thanks, Peta. I agree Hydrangeas are wonderful in our climate. Your special ones sound lovely. Deirdre

5/14  Ambra - 2010 (Zone:10 - Warm Temperate) Monday, 11 February 2013

Ours too were burnt horribly in the hot summer sun. One day the temperature was 46 deg in Sydney and the next morning the whole bush was burnt to a frazzle, so I pruned it a week later. Hope it"s not too early but it was sad to see it looking so miserable.

6/14  Janet - 4211 (Zone:10 - Warm Temperate) Monday, 11 February 2013

I have always loved hydrangeas, but have never had any luck with them since living on gold coast. I have purchased one and intend to keep in a pot and in a semi shaded area. Thank you for your advice - very helpful. Good luck with them - hope they do OK for you. It"s easier to control the conditions for them in a pot. Deirdre

7/14  Jennifer - 3056 (Zone:10 - Mediteranean) Monday, 11 February 2013

I have 2 H. quercifolia and was wondering when to prune them? The flowers are now brown after the heat in Melbourne and there is some new growth. I am not sure whether to leave the flowers or remove them. Any advice? I don"t do much with mine, just remove the dead heads - which you could do now. If it is getting too big you can take out branches that are in the way but I have found that hard pruning reduces flowering next time. That is in Sydney, anyway. Deirdre

8/14  Julie - 4510 (Zone:11A - Sub-tropical) Monday, 11 February 2013

Thanks for the lovely post about hydrangeas. Even though I am a mainly unsuccessful grower of hydrangeas, I always keep trying, because I love them so. My childhood ( Queensland) memory is of the woman next door with them planted along the shady south side of the house. Dont know if they even got morning sun. They were always pride of place on the Christmas table. Will try again in v shaded spot. Love the paniculata, quercifolia and quadricolour. But maybe the blue deckle is more robust. Thanks, Julie. I have found the macrophylla ones the toughest in Sydney but certainly that Blue Deckle mentioned in the comments today sounds fantastic! Deirdre

9/14  Margaret - 2122 (Zone:10 - Warm Temperate) Monday, 11 February 2013

Thanks for your interesting blog, as usual. I have a lovely white hydranges, which, unfortunately, always seems to flower when the days are very hot, and so gets burnt, although it is in a morning sun position. My "Endless Summer" hydrangea is somewhat disappointing, as the thin stems mean the flowers hang down. I agree about "You and Me", it is a very desirable plant. I have a semi-double flowered hydrangea, name unknown, brought from my parents" house - always flowers well. Yes a good point about the Endless Summer ones tending to become a bit pendulous with the weight of the flower heads. I haven"t had that problem with You & Me - it is still sitting up nicely even though smothered in ageing flower heads - I am very pleased with it. I love the double-flowered and semi-double macrophylla ones - I have several of them and don"t know their names either! Deirdre

10/14  Margaret - 2067 (Zone:10 - Warm Temperate) Monday, 11 February 2013

I loved your blog on Hydrangeas.They are my absolute favourites. I think this goes back to childhood memories. I have a "You & Me" in a pot and got no flowers this summer. Should I prune or leave it this year. I have very old "Lacecaps" which have grown to about 9ft high. I only deadhead them as they hide a paling fence. It is a huge job every year but they always give a lovely show. I find a lot of little plants pop up around the garden as the "Lacecaps" have fertile flowers. Maybe just leave that "You & Me" one this year and see what happens next year. I don"t prune my lacecaps very hard - just remove the deadheads as you do. Interesting about the self-seeding as I have never had that happen to me! Deirdre

11/14  Robin - 2121 (Zone:10 - Warm Temperate) Tuesday, 12 February 2013

Enjoying the cooler conditions and rain currently in Sydney. If this keeps up I will be moving some hydrangeas in Autumn. Some certainly perform better in mulched pots and sulk when planted in the ground in my garden(clay base with root competition). Thanks for the timely blog and pruning tips. I agree re pots are good when there is too much root competition. I think the best ones for pots may be the smaller-growing ones rather than the very big ones. Deirdre

12/14  Pam - 2159 (Zone:10 - Warm Temperate) Wednesday, 13 February 2013

I came across your website when I was checking the spelling of Tulbaghia cominsii. My hydrangeas have suffered with the heat and dryness too. The blooms have mostly been smaller, and they have faded and scorched more quickly. However, my H. paniculata has been looking good, and they are just turning pink and fading. H. aspera var villosa is just starting to flower with its mauve flowers, and white sepal flowers. With regard to seedlings, they often come up on my shadehouse floor. Thanks, Pam. My Hydrangea aspera var. villosa is just coming out too and it hasn"t yet been affected by heat. It is a lovely one - quite different to the rest. Interesting about the seedlings coming up. Do you pot them up to grow on? Deirdre

13/14  Pam - 2159 (Zone:10 - Warm Temperate) Wednesday, 13 February 2013

Hi Deirdre, Yes, I do pot many of them on. I suspect most of the seeds are from an "old" lacecap, possibly "Seafoam" which flowers prolifically, but not very spectacularly. I often pot cuttings for friends as it is a good backdrop and copes with sun. Like all growers of seeds I live in hope one plant will be something extra special. Thanks, Pam. I never knew Hydrangeas could self-seed till now! Seafoam sounds a good doer. And you never know with those self-seedlings what you might get one day! Deirdre

14/14  Marinka - 2041 (Zone:10 - Warm Temperate) Friday, 15 February 2013

I have also done a light prune on my hydrangeas, removing the spent flower heads (mine never turn those nice autumnal shades, they just look faded & dull) & some burnt leaves. I was able to cover mine with sheets for the first 40 degree day but was unable to do so for the second, worse one. I actually always do a double prune on mine, in mid to late autumn, then again in winter. Mine are 10 mop heads & 2 popcorn ones. Thanks, Marinka, sounds like you have a great collection. Covering them with sheets does help if it is possible to do it - not always possible, unfortunately. Deirdre

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