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Hydrangea Care Calendar – Part 2

Hydrangea Care Calendar – Part 2

By Stacey Hirvela, introduction by Natalie Carmolli, Proven Winners® ColorChoice®
Photographs courtesy of Proven Winners® ColorChoice®

Following up on last month’s article, here is a handy care calendar for those who have hydrangeas that bloom on old wood, meaning they set their flower buds on the current season’s stems. These types are oakleaf hydrangeas (H. quercifolia) as well as some bigleaf (H. macrophylla) and mountain (H. serrata) hydrangeas.

Examples of hydrangeas that bloom on old wood are the Gatsby series of oakleaf hydrangeas, the Cityline® series of bigleaf hydrangeas and ‘Bluebird’ mountain hydrangea. Keep in mind, not all bigleaf and mountain hydrangeas bloom exclusively on old wood, there are many reblooming varieties that set buds on old and new wood. Those cultivars include the Let’s Dance® series of bigleaf hydrangeas and the Tuff Stuff™ series of mountain hydrangeas. While all hydrangea types can be safely cared for using the calendar below, old wood bloomers will not perform well if they are treated the same as a reblooming variety.

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Cityline Mars bigleaf hydrangea.

Hydrangea Care For Old Wood Bloomers – Bigleaf Hydrangea (H. macrophylla), Mountain Hydrangea (H. serrata), Oakleaf Hydrangea (H. quercifolia)

March/April – These hydrangeas start to emerge around this time, depending on the weather. Once you see the new growth beginning to appear on the stems, you can safely cut off any portions of the plant that aren’t showing signs of life, as well as any old flower heads that are still clinging to the plant. Do not prune these types of hydrangeas any more than what is described here – they have already formed their flower buds for the coming summer, and pruning beyond this amount will remove those flower buds.

March is also a good time to transplant these hydrangeas, if desired. This is typically a pretty straightforward job since hydrangeas are shallow-rooted. It’s best to transplant when the plants are still dormant. Save any pruning for after transplanting – that gives you the chance to repair any branches that may have broken during the moving process.

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Gatsby Pink oakleaf hydrangea.

Once bigleaf and mountain hydrangeas begin to emerge, keep an eye on the weather for any spring frosts or freezes, as their delicate new foliage is very sensitive to cold and these extremes can damage the developing flower bud, destroying the chance of bloom. If a frost or freeze is forecast once the plant is showing green, cover them with an old sheet or blanket for the night. This provides enough protection to prevent the cold air from contacting the green leaves and buds; remove the sheet the next morning, when the danger of frost has passed. Oakleaf hydrangeas are not as sensitive to late season frosts and freezes and should not require protection.

This is also a good time to begin fertilizing, especially if your plant experienced significant winter damage. Use a granular fertilizer formulated for woody plants, like a rose fertilizer.

If slugs are an issue in your area, begin treating now, as eggs hatch in late winter/early spring.

If you wish to change the color of your bigleaf or mountain hydrangea, get your soil tested through your local cooperative extension now. This will help you determine what treatment you need to use to affect the color change.

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‘Bluebird’ mountain hydrangea.

May – Fertilize if desired, one month after previous application. If you have a reblooming hydrangea that blooms on old and new wood, monthly fertilizing is recommended for best results. This is also a great time to put down a 2-3” layer of shredded bark mulch to keep the roots cool and moist in the coming heat. Repeat the frost protection outlined above through May if needed.

If attempting to change the color of your hydrangea, treatment based on the results of your soil test should begin now.

Begin supplemental irrigation if weather has been hot and dry.

June – Bloom time begins for these three hydrangeas in most areas.

Fertilize if desired, one month after previous application. You may need to begin providing supplemental water at this point if the weather is hot and dry – if these hydrangeas dry out severely during their bud development or bloom time, the flowers will turn brown and wilt instead of aging gracefully.

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Let’s Dance ¡Arriba!reblooming hydrangea.

July – Bloom time begins in cooler areas; rebloom (i.e., new wood flowers) may begin on bigleaf and mountain hydrangeas in warmer climates. Flowers may be cut for fresh arrangements, but do not cut flowers that are freshly opened, as these wilt quickly. Florets should feel dry and slightly papery before cutting.

You may deadhead spent flowers if you wish – follow the stem back to the first set of buds below the spent bloom and cut just above them. This isn’t strictly necessary, it’s a matter of personal preference.

Make the final fertilizer application of the year by late July. Continue supplemental watering as needed. If you find your hydrangea is constantly wilting, make a note to move it the following spring to a more favorable spot.

August – Now is a good time to cut flowers for drying if desired. Whatever color you cut them at is the color they will keep once dry. Rebloom should be continuing on reblooming bigleaf and mountain hydrangea varieties.

You may deadhead spent flowers if you wish – follow the stem back to the first set of buds below the spent bloom and cut just above them. This isn’t strictly necessary, it’s a matter of personal preference.

Continue supplemental water as needed.

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Tuff Stuff mountain hydrangea.

September – Flowers can still be cut, if desired. You may deadhead spent flowers if you wish – follow the stem back to the first set of buds below the spent bloom and cut just above them.

October – Your hydrangea is most likely going dormant at this point and needs little to no attention. If your plant developed any leaf spots over the season, it’s a good idea to remove and discard the fallen foliage to minimize the chance of reinfection for next year. Though most leaf spots do not harm the plant in any significant way, they can be a bit unsightly. Add or top up mulch to maintain a 2-3” layer for winter protection.

As your plant goes dormant, resist the urge to cut it back or prune it. Bigleaf and mountain hydrangeas both look like they should be cut back as part of a normal fall cleanup, but doing so will remove all of the flower buds for the following season. When in doubt, don’t prune!

November/February – Plants are dormant. Flower buds for the following season are already set within the stems, waiting for next summer to bloom again.

And that’s it! No matter what type of hydrangea you have, or are planning on adding to your garden, once you establish a care calendar that works, these floriferous plants will give you months of beautiful blooms in return.

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