Covering Hydrangea's in MO

bluebell_in_moOctober 8, 2009

How soon should I cover my hydrangea's for winter protection. Will frost kill the new buds or does it take a hard freeze? I live down in a valley by a creek and we get early and late frost, so I never know when to cover and uncover them.


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luis_pr(7b/8a Hurst, TX)

Hello, bluebell_in_mo. If the plants are starting go into dormancy and temperatures are going to merely go to freezing or slightly under, that should not affect the buds. A gradual downhill move of temperatures, in other words, should not kill the buds. Keep in mind that a plant that is hardy to Zone 7 -just an example of what most hydrangeas can handle- should be able to withstand temperatures from 0 to 5 degrees, the definition of hardiness of Zone 7. Zone 6 is defined 10 degrees colder, Zone 5 another 10 degrees colder and Zone 4 yet another 10 more degrees colder. So merely going below freezing gradually should not kill the buds. It is the sudden changes/dips that cause me to go into oh-darn-mode.

By checking when your average date of early frosts is, you can be prepared to cover them. Since the date is an average, be ready to winter protect 2-3 weeks before the average date. More if your winter temperatures fluctuate a lot. Many times hydrangeas will go dormant before that but, in some years you may be forced to jump the gun if it stays warm for too long and a big dip is forecasted. You need to keep an eye on the weather forecast now; visit and check the 10-day forecast often. Mulch (3-4"), normal cold temps, reduced light levels and no fertilizing starting in July should help your shrub go dormant and should protect it during winter. But stay vigilant; check the 10-day forecasts often for help in deciding exactly when to cover. Local nurseries can also help you choose the exact time. Ask them or observe when do they move tender plants into more secure nursery locations. As soon as they do that, put the chicken wire, collect leaves and review the local forecasts. Then add the leaves when the weather does turn colder or if you hear about a sudden dip after a warm spell.

Wouldn't it be nice if someone just called you or sent you an email instead? Hee hee hee. In this warmer region, we do not winter protect but that does not mean we are immune. There was one year in the last 30 when temps in the 70s lasted until mid-December. Then we got hit by a whole week of freezing weather that managed to kill the buds because the plants were fooled into staying in "growth" mode. Under those conditions, it is hard to protect the shrubs and trees. Buds got zapped but stems were fine. I got a total of 2 hydrangea blooms the following Spring. Oh well. But this is sooo unusual that, well, almost no one here winter protects.

So I suggest that you place the chicken wire early based on historical temperature and frost trends & local nursery suggestions. Collect leaves in plastic trash bags early so they are good and ready. Add the leaves if you hear of sudden temperature dips or add them 2-3 weeks before the avge date of early frosts. A few minor dips below freezing may be all it takes to prod the hydrangeas into a winter slumber. But again, it is the wild and sudden dips that you should look out for.

You did not say what hydrangea you have but if you have one of the Teller lacecap hybrids (which are frost tender), I would winter protect a little earlier. Suggestion: unused leaves can be left in trash bags; some settling usually occurs by mid winter and you can add more leaves easily if you have a stack of unused leaves stored somewhere.

Of all the frosts, I view late frosts as the most damaging generally speaking. Frosts tend to flow down a hill unless impeded by something like a hedge so have that in mind if it applies to your hydrangeas and your garden.

Going the other way around now -uncovering them- can also be a hit and miss thing too. A general rule of thumb would be to uncover the plant 2-3 weeks after your last average date of frost. Make it longer (3-4 weeks) if Mother Nature catches you off guard often. Again, local nurseries can tell you when that is for you and can suggest a certain number of weeks above that average. But like I said, winters tend to vary a lot some places. So observe the 10-day forecasts at to monitor the weather on any given year. If it looks safe then uncover. Do not take the cues from the hydrangeas themselves because the silly things will try to begin leafing out as soon as there is a warm spell. When you uncover them, there may be some stems that turn white or white-ish looking but that should go away in 1-2 weeks. Should you uncover and the buds get zapped by a late frost, the plant itself should not be killed. Learn from that and delay uncovering in future years.


    Bookmark   October 9, 2009 at 4:08AM
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Thank you Luis, lots of good information. I try to watch the weather forecast, and our first frost is supposed to be tonight, so maybe I will throw something over them on the frosty nights until I get them covered for winter, I have nice plants but no blooms if I don't cover them good and still don't have many blooms sometimes. The only way I have lots of blooms is to lay potted ones down and cover them. They are so heavy to lug around that way. These are mopheads and a few years old. I guess if I want those big beautiful blooms, there's just no easy way. Wish they could all be like old faithful Annabelle that never fails to bloom.
Thanks again for taking the time to respond,

    Bookmark   October 9, 2009 at 11:52AM
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luis_pr(7b/8a Hurst, TX)

I hear you, bluebell. MO can be very cold in winter so protection is needed in many places. I recall you even have a few spots (here and there) with Z4 ratings on the USDA Map so continue protecting those mopheads. They now have a pink Annabelle for sale in limited places. It may work well there if you are into pink-only blooms. I am sure they are working on a "new faithful" blue Annabelle next(?!?!?). Ha!

    Bookmark   October 10, 2009 at 3:16AM
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We had ice in any standing water Fri. morn and so much frost on the roofs, it looked like it had snowed. Looks fine this morning, but you never know in MO, we had a really nice summer. I really like having seasons though, I've lived here all my life. The pink Annabelle sounds interesting, and yes, I am into the pink blooms, I love the ones that dry papery and have shades of burgundy & green. I sometimes put them in a vase of water if they aren't quite ready to dry to keep them from wilting and they do pretty good.

    Bookmark   October 11, 2009 at 8:18AM
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