It’s finally time to prune your old wood hydrangeas. This is in addition to what I wrote in February of this year about hydrangea pruning. At that time I wrote it was safe to prune your panicle and woodland hydrangeas in late winter. If you haven’t already done that, get going unless you live in the milder parts of the country where you are long past your deadline for this task.
Now for hydrangea pruning of big leaf (macrophylla), mountain (serrata), oak leaf (quercifolia) and climbing varieties.
Consult Your Long Range Weather Forecast
The good news is that if you look ahead to the 10 day forecast, you won’t see any freezing night temps in growing zones 5 and 6. That timing takes you past your average last frost date which is your green light. Time to get going on pruning big leaf and mountain hydrangeas, as well as other old and new wood plants in this family.
The reason you needed to wait is that if you removed – even just deadheaded – rebloomers prematurely, you would have stimulated their “sleeping buds” to initiate growth. Those new growth/buds could have been zapped by a late season freeze. Now thanks to the wonder of technology, you are assured that the buds you will stimulate will not be affected by damaging cold temps. Of course, you will still need a forgiving summer to get the later season flowers from your rebloomers. The best you can do for them is fertilize and irrigate properly as the season progresses.
Exactly What To Do
Exactly what do you need to do now to finish pruning of old wood flowering hydrangeas (big leaf, mountain, oak leaf, and climbing)? Yes, you need to see “broccoli” before taking your final cuts. But at least now, you can freely dead head (remove spent flowers) and clean up your plants, even the rebloomers.
Cut off those dead flowers of your big leaf and mountain hydrangeas just above a set of live buds. You don’t know yet if the buds on the stems or tips of your plants are flowers or just foliage so don’t cut other than the dead flowers.
Also go after any clogged trunks you may have at ground level. That will improve air circulation, and deprive insects of hiding places. Of course, you need to be careful not to inadvertently knock off any new growing buds that may have emerged.
I have been using a cordless leaf blower to clean the base of my plants. It works great since I can control the speed of the air blast and I don’t have to be on my knees to get the job done. But if you have had problems with insects like thrips, you may want to use a shop vac. That way you have your best shot at removing the insects before they can get established.
The Importance of Garden Sanitation
Remember to take the time to disinfect your pruning tools as you move among your plants. You want to start clean and stay clean this season and being manic about sanitation is critical. Any of the commercially available sprays will work fine– we all know about them as a result of Covid, right? You can also use a simple bottle of rubbing alcohol from the drug store to do the job. Disinfectant wipes can also come in handy.
Climbing and Oakleaf Hydrangeas
I am delighted to see my climbing hydrangeas are showing flower buds now. If yours are as well, freely cut away the dead, diseased, and damaged wood and any wayward branches. You can clearly see where the flowers are so you may want to wait until they have bloomed to take any final reshaping cuts.
Oak leaf hydrangeas are displaying growth at their tips which indicates which stems are alive. If an oakleaf hydrangea stem has no top growth among others that do, you can be sure you won’t see a flower on that stem. So again, freely cut away any flowerless stems and dead wood (at the base of the plant).
What’s the Best Tool To Use
You can use your pruning saw to get at these stems or invest in a cordless reciprocating saw (sometimes called a “Sawzall”). I have been using the reciprocating saw for the first time this season and it makes the job much easier.
Do I Need To See “Broccoli” On My Old Wood Hydrangeas?
Without seeing “broccoli,” it would be foolish to prune old wood plants any further. Once the “broccoli” emerges, then it’s safe to cut your stems lower, either to reshape the plant or get it under control. Of course, if you find yourself doing this every season on the same plant, I would suggest you consider moving that plant to a place where it can grow to its intended size, or donating it. Then replace it with one of the newer more compact varieties that will be better suited to the space you have.
Can You Just Deadhead
Pruning your big leaf and mountain hydrangeas can be as simple as deadheading all the old flowers. Period. But you might also take the time to remove any diseased, damaged, and dead wood. Consider going further down the plant – carefully – to remove the leftover dead stubs from prior year’s cuts. This is where the reciprocating saw really works well.
Look for branches that are crossing or rubbing with another, and any that are growing toward the inside of the plant. I would also encourage you to remove any stems thinner than a pencil as they will not produce a flower. Those skinny stems will rob your plant of the energy it needs for the stronger stems.
Once you have made all your cuts, take the time to fertilize your plants with a granular fertilizer that is labeled for shrubs. Rose fertilizer is ideal.
Stay away from 10-10-10 as no plant uses nutrients in the same amounts and all those products do is contribute to pollution and runoff. You could also add compost but don’t fool yourself into thinking it is a substitute for fertilizer.
Check the Irrigation
Inspect your irrigation if you have it. Soaker hoses should be laid a few inches from the base of the plant and ideally buried under a layer of mulch. Speaking of mulch, check that it is at least 2 inches deep all around and doesn’t touch the base of your plant.
And that’s it! Your plants will thank you for this care and feeding. And you will enjoy the rewards of your efforts.
UPCOMING SPEAKING DATES
With Covid restrictions easing, I am thrilled to be back in front of live audiences. I am continuing to book talks, both virtual and live (HOORAY!!!). If you are interested in having me speak to your group, just click HERE and you will be taken to the “Contact Me” page of my site to begin our dialogue. I cover lots of other topics besides hydrangeas, as you will see when you click on “SPEAKING TOPICS”. All my talks are 5-star rated, so you won’t be disappointed.
Here are my upcoming public talks for the next few weeks:
May 7, 10.00 am – 1 pm: (YIKES!! That’s this Saturday!) Shady Characters, New York Botanical Garden. Format: In person. Cost: Member – $65; Non-member – $69. Learn about shade gardening, what to do and how to do it.
For longer range planning, I am pleased to tell you that I am speaking on July 8 at this year’s Cape Cod Hydrangea Festival. The details of the full program are still being developed, but if you want to be on the Cape for its prime hydrangea season, now is the time to get your ducks lined up and maybe make hotel arrangements.
So tell/bring your friends. I would love to meet you – finally!!
Thank you for reading.
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