5 Common Mistakes Gardeners Make with Hydrangeas in the Fall – And How to Avoid Them!

Fall comes and your hydrangeas have done a wonderful job in your garden. Some may still have their large blossoms in September, but, of course, all that effort has cost these generous shrubs a lot of energy, and we all want to give them some tender loving care… But be careful! Sometimes, too much love and attention is a big mistake. On the other hand, we often forget to give them what they actually need. These errors can cost you a lot next year, when they start growing new leaves and prepare for a new flowering season.

So, if you really love your hydrangeas, check out these 5 common – but dangerous – mistakes many amateurs make in the fall and avoid them!

Common Fall Hydrangea Mistake Nr 1 – Feeding Them in Fall

Common Fall Hydrangea Mistake Nr 1 – Feeding Them in Fall

Oh yes, hydrangeas use up an awful lot of energy to grow all that lush foliage and spectacular blooms, so, you may be tempted to give them some food when fall comes. But fertilizing hydrangeas in this season is dangerous.

To start with, forget any fast-release liquid fertilizers, and if you really see that your hydrangea is tired, act by the end of summer, using a balanced 10-10-10 organic slow-release fertilizer (or compost) at low dosage. You can stretch it to the beginning of September, but no later.

“And why?” you may ask… Well hydrangeas are easily fooled, so to speak. If you fertilize them in the fall (especially with liquid products), they may think that spring has come and produce new buds. Then frost arrives and the damage will carry on to the next season, with poor foliage and flower growth.

Common Fall Hydrangea Mistake Nr 2 – Pruning Old Wood Varieties

Common Fall Hydrangea Mistake Nr 2 – Pruning Old Wood Varieties

So, your hydrangeas have grown big and thick? Fine, you may think it is time to give them a good pruning. And this is a very common mistake indeed! You can prune some hydrangea varieties in fall, but not all of them…

Yes, because hydrangeas are divided into two types, new wood varieties blossom on new shoots, old wood species bloom on old stems. So, you can prune the former in fall, because they will only grow new buds next year, but if you do it with the second group, you will cut the future flowers too.

This is because they start producing new flower buds soon after they have finished blooming. So, you have two weeks after blossoming to prune old wood hydrangea varieties, and these are:

  • Bigleaf hydrangea (Hydrangea macrophylla)
  • Oakleaf hydrangea (Hydrangea quercifolia)
  • Climbing hydrangea (Hydrangea anomala subsp. petiolaris)
  • Mountain hydrangea (Hydrangea serrata).

On the other hand, you can prune panicle hydrangea (Hydrangea paniculata) and smooth hydrangea (Hydrangea arborescens).

The weird case concerns reblooming hydrangeas (they are cultivars of Hydrangea macrophylla); they blossom on both old and new wood. The idea is not to prune them, unless necessary, in which case, you will lose some blossoms, but not all.

Common Fall Hydrangea Mistake Nr 3 – Not Improving Soil Drainage

Common Fall Hydrangea Mistake Nr 3 – Not Improving Soil Drainage

Do you realize how many leaves hydrangeas produce over the growing and flowering season? That’s all organic matter that, unless you pick it up meticulously, ends up on the soil. And it holds moisture… Do you realize how much water they drink over a year? And it washes away drainage underground.

So, if you really love your climbing or shrub hydrangeas, remove the mulch in fall and then give them a few inches (2 is enough, or 5.0 cm) of coarse gardening sand (or gypsum for heavy clay soil). The rainy season is coming and stagnant water underground can damage their roots. What’s more, as winter temperatures drop, it may freeze, causing extra problems.

So, no food but lots of drainage for your hydrangeas in fall! Don’t get these two mixed up! And, by the way…

Common Fall Hydrangea Mistake Nr 4 – Overwatering!

Common Fall Hydrangea Mistake Nr 4 – Overwatering!

Ok, hydrangeas like a lot of water, especially in summer, but as winter comes, they stop blossoming, and they slowly start going into dormancy. This means that by the end of the season their metabolism has slowed down to a minimum. And what does this mean? It means that they need less water.

Add the fact that fall is usually a wet season, and you can see how easy it is to overwater them. In fact, in most countries (in temperate and cold regions) you can stop watering hydrangeas altogether in fall.

Potted hydrangeas may need a bit more water, but do check that the top 2 inches (5.0 cm) of soil are dry. Of course, if the weather is particularly dry, you can make an exception and an inch or two of water (2.5 to 5.0 cm) will be welcome in this case. But always adapt to rainfall!

Common Fall Hydrangea Mistake Nr 5 – Not Mulching…

Common Fall Hydrangea Mistake Nr 5 – Not Mulching…

So, you removed the mulch to improve drainage? Now it’s time to replenish it (or change it)! If you don’t, you will get two problems: soil temperatures can drop to below freezing, and, ok, hydrangeas are quite cold hardy, but you want to avoid frost around their roots, especially if they are young and / or newly planted.

Next, the heavy rains will wash away both nutrients and drainage over the cold season; yes, they are dormant, but they still need some food, and then… Keeping the soil healthy and well drained during winter is essential to get a great start from your hydrangeas in spring.

Common Fall Hydrangea Mistake Nr 6 – Not Deadheading

Common Fall Hydrangea Mistake Nr 6 – Not Deadheading

I know, there are some gardeners who leave the hydrangea blossoms on all winter! True, they can still look attractive, even when they are dry, but… To start with, they stop ventilation, and during the cold and wet season, it is essential for their health.

Next, they withhold moisture in the best case scenario, and in the worst case, they can rot away; this will bring diseases, fungi and molds.

So, always deadhead your hydrangeas in fall; you can leave the blossoms to dry on the branches if you want, or pick them off as soon as they are spent (it looks better), and remember – they make excellent dried flowers!

6 Common Mistakes to Avoid in Fall for Great Hydrangeas Next Year

I am sure you really love your hydrangeas, so, avoid these widespread mistakes, and they will pay you back next year, with their fresh and lush foliage, and jaw dropping floral displays!

Amber Noyes

Written By

Amber Noyes

Amber Noyes was born and raised in a suburban California town, San Mateo. She holds a master’s degree in horticulture from the University of California as well as a BS in Biology from the University of San Francisco. With experience working on an organic farm, water conservation research, farmers’ markets, and plant nursery, she understands what makes plants thrive and how we can better understand the connection between microclimate and plant health. When she’s not on the land, Amber loves informing people of new ideas/things related to gardening, especially organic gardening, houseplants, and growing plants in a small space.

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