Are All Hydrangeas Perennials or Annuals?

Hydrangeas are perennial shrubs, meaning they come back every year, unlike annuals that die off after just one season.

That said, sometimes hydrangeas that come from greenhouses or are sold as gift plants are considered annuals because they die off soon and don’t come back after that.

But this is not because they aren’t perennials, it’s because they’re not winter hardy in the area they’re commercialized in.

In this article, I discuss the particularities of perennial hydrangeas and how you can help ‘gift hydrangeas’ survive beyond just one season.

Perennial Hydrangeas

Hydrangeas are herbaceous or woody perennials that go dormant in winter and come back in spring, shooting new growths and producing blooms throughout spring and summer.

The reason why some hydrangeas might be mistaken for annuals is that they’re not cold tolerant in zones 5 and die off because of the winter frost.

With temperatures that can dip to -20 degrees in zones 5, hydrangeas that aren’t frost-tolerant don’t stand a chance of coming back in spring.

But some hydrangeas are indeed root-hardy. Smooth hydrangeas, panicle hydrangeas, and oak-leaf hydrangeas perform well in zones 5 to 9.

One of the least frost-resistant hydrangeas is the big leaf hydrangea, which does not do well in zone 5 unless it’s container grown and it’s moved inside during winter.

Hydrangeas that come from greenhouses are difficult to keep alive, and not necessarily because they’re not cold-tolerant. These often die even when kept indoors.

One of the reasons why these hydrangeas fail to survive is because they come in small pots that dry out too quickly, causing dehydration in hydrangeas.

Therefore, the first thing you need to do when you receive a gift hydrangea is to move it to a larger pot. Make sure to use a well-draining potting mix and keep the soil moist with regular watering.

Lack of enough light is another factor that will potentially shorten the lifespan of these potted hydrangeas. Move them outdoors during summer and keep them indoors during winter.

Will Potted Hydrangeas Survive Winter?

If left outdoors potted hydrangeas that are not cold-tolerant will not survive the winter. These hydrangeas need to be moved indoors, away from cold winds and frost.

But moving them indoors does not mean putting them in a well-heated room. You want to move these hydrangeas to a cold room, with temperatures of around 45 degrees F.

The reason for this is that hydrangeas need cold during winter to enter into dormancy. Without the possibility to go dormant, a hydrangea will slowly lose its vigor and eventually die off..

Do Hydrangeas Lose Their Leaves in Winter?

Yes, hydrangeas start losing their leaves in the fall with cold temperatures setting. In winter, they completely lose their leaves, and they appear as if they’ve died out.  Don’t worry, this is typical of deciduous shrubs.

Hydrangeas may lose their leaves in winter, but not their stems. In spring they produce new growths, then buds and blooms, going through this cycle on and on for several seasons.

If the temperature in your area does not drop below 0 degrees F, you don’t need to worry about setting up winter protection for your hydrangeas.

Established hydrangeas are also hardier compared to young hydrangeas.

1. arborescens and H. paniculata survive down to negative 30 degrees F, but these too require winter protection should temperatures drop to negative 40 degrees.

If you need to set up winter protection for your hydrangeas, think in terms of insulation (burlap, insulation cloth, polytunnel, etc.). Set up a wire cage and add layers of hay, pine straw, dry leaves, and cover the root area with a thick layer of compost.

Don’t remove any of the insulation before the last winter frost. You don’t want to be taken by surprise by an early spring frost that can damage new growths.

If a late frost does set in after you’ve removed the insulation, cover the shrub with blankets, burlap and any other insulation. Make sure to cover all the way down to the ground.

Can You Keep Hydrangeas Indoor?

Indoor growing isn’t the ideal environment for hydrangeas. These plants thrive outdoors, in full sun or partial shade and do best when they are planted in the garden.

When grown exclusively indoors, hydrangeas struggle if they’re not looked after properly. They can lose their vigor, struggle with dehydration, and eventually die off.

Here are some tips to maximize the chances of your hydrangeas surviving indoors:

• Transplant your hydrangea to a larger pot if it comes in a small pot. This will ensure that the potting mix doesn’t dry out as quickly, keeping the soil moist for longer and your hydrangea better hydrated
• Use a well-draining potting mix rich in organic matter
• Find a bright spot for your hydrangea where it gets plenty of sunshine throughout the day, but don’t place it under direct sunlight
• Maintain a good watering routine and increase moisture around the plant if the air gets too dry indoors
• Fertilize your hydrangea with a fertilizer formulated especially for acid-loving plants
• Keep in a cold room (45 degrees F) during winter and maintain temperatures between 50-60 degrees F during the rest of the year

Hydrangeas have trouble blooming indoors, but you can trigger blooming if you manage to alter temperature conditions, so the hydrangea thinks winter is coming and it’s time to enter into dormancy.

Since there are many points of failure in keeping hydrangeas exclusively indoors, you can work out a system whereby you keep hydrangeas outdoors in a planter or pot during spring, summer and fall, and move them into the garage or other cold area during winter.

Wrap Up

As perennial plants, hydrangeas go dormant during winter, only to come back to life again in spring. The way you prepare your hydrangea for winter (e.g. pruning or winter protection) will determine how well your hydrangea will do in the next season.

If your hydrangea is cold tolerant and winters aren’t frosty in your area, all you need to do is wait for spring to come to see your hydrangea coming back with new growths, lush foliage, and impressive blooms.