Hyacinth lovers all over Cape Cod are checking the weather forecasts for March 21st and 22nd to see if the twenty - degree temperature will suffer their flora ’ buds . We are very distressed about damage to our signature plant this twelvemonth after last year ’s Polar Vortex , which toss off most of these shrubs to the ground and made them flower less . Here are our cerebration :
Hydrangeas are a beloved garden shrub , treasure for their lush heyday in ghost of pinkish , blue , majestic , ruby-red , and blank . However , these smasher are also somewhat finicky when it comes to inhuman tolerance . Understanding how well your hydrangeas can withstand freeze temperatures is cardinal to hold on them healthy and floriferous .
The Different Types of Hydrangeas Have Varying Cold Tolerance
There are several different types of hydrangea including
Bigleaf hydrangea ( Hydrangea macrophylla ) – The most unwashed type maturate in gardens Blooms on old wood .
Oakleaf hydrangea ( Hydrangea quercifolia ) – Named for its typical leaf . Blooms on old Ellen Price Wood .
Mountain hydrangea ( Hydrangea serrata ) – A smaller shrub with delicate bloom . flower on old wood .
Panicle hydrangea ( Hydrangea paniculata ) – Large , strobile - shaped blooms . peak on new wood .
fluid hydrangea ( Hydrangea arborescens ) Blooms on new Mrs. Henry Wood .
Climbing hydrangea ( Hydrangea anomala subsp . petiolaris ) – A vine metal money . blush on old wood .
The key thing to note is that bigleaf , oakleaf , spate , and rise hydrangea all bloom on erstwhile Sir Henry Wood . This means their bloom bud emerge in summertime and must pull round the wintertime to flower the following twelvemonth . Panicle and smooth hydrangea salad days on new wood that grows each spring , making them better selection for insensate clime .
Can Hydrangea Roots Survive Winter Cold?
The root system of most hydrangeas is quite robust and can support very depressed temperatures . Bigleaf , oakleaf , and mountain hydrangeas have been love to survive temperatures as abject as -15 ° F ( -26 ° C ) at the root stratum .
However , the above - earth parts of these plant , including the stems holding the flower bud , are less cold hardy than the solution . This disparity excuse why many gardener have the experience of hydrangeas not blooming after a frigid winter , even though the shrub itself survives .
What Temperature Kills Hydrangea Blooms?
Hydrangea macrophylla , serrata , quercifolia , and anomala heyday buds can typically withstand temperatures down to roughly -5 ° F ( -20 ° C ) before sustaining damage . However , a period of unusually ardent weather in late fall can negatively bear upon their cold hardiness .
If temperature drop rapidly from the 60s and seventy F down to below freezing , cutter growth and flower bud will be much more susceptible to damage . A surd frost of 25 ° F ( -4 ° C ) or below can obliterate exposed bloom during such precipitous cold snaps .
In general , temperature of 20 ° F ( -7 ° vitamin C ) or below may compromise overwintering hydrangea flower buds . And during an extreme inhuman outcome , such as temperature dipping below 0 ° F ( -18 ° C ) , most previous - Mrs. Henry Wood hydrangea efflorescence will belike be lost .
Protecting Hydrangeas from Winter Damage
If you live in an area with winters that sink below the idealistic temperatures for your particular hydrangeas , there are some prank to help protect them :
Choose protect location out of the idle words . The desiccate effect of wintertime winds can harm buds even if the temperature itself is not extreme .
enfold or isolate pots for container - grown plant .
Mulch around the base of in - ground hydrangea . Aim for 3 - 6 inch of sliced leaves , evergreen boughs , or other constitutional materials .
Erect a temporary barrier such as burlap supported by stakes to harbor plants from nothingness .
Water well in late fall so ground are moist heading into wintertime . Dry soil worsen the issue of coldness .
hold antidesiccant spray to leaf in early wintertime . intersection like Wilt - Pruf form a protective film against moisture exit .
Delay rationalize until spring so old woods stay inviolate , insulate bud .
prefer moth-eaten - broad hydrangea species and cultivar known to be reliable in your climate . Oakleaf ( H. quercifolia ) , smooth ( H. arborescens ) , and panicle ( H. paniculata ) type are in force choices for colder regions .
The Impact of Fluctuating Winter Temperatures
Sudden temperature change in wintertime can be just as damaging , if not more so , than sustained flow of frigidness . For example , a stretch of comparatively fond day in February may goad hydrangea to break out dormancy too early . Subsequent hard freeze can then kill newly emerged tender growth .
These erratic swings from freezing to thawing and back again are unfortunately becoming more common due to climate modification . Choose planting sites with protection from harsh winds to facilitate cushion hydrangea from these ups and down as much as possible .
Selecting Cold-Tolerant Hydrangea Varieties
While hydrangea macrophylla mintage are only rat hardy to zone 5 or 6 , some prodigious cultivar have proven themselves in even colder climate .
When snitch for hydrangeas , look for selections described as run winters in zones 4 or even geographical zone 3 . Here are some great choice :
For Bigleaf Hydrangea
Endless Summer ® serial publication – multiply to rebloom on both onetime and new wood . The original Endless Summer is stag for geographical zone 4 . Newer introductions like Blushing Bride and Twist - n - vociferation are typically district for 5 or 6 .
Let ’s Dance ® series – Reblooming bigleaf hydrangea serial publication multiply for cold hardiness to zone 4 . Varieties admit Blue Jangles , Diva , and Rhythmic Blue .
Lady in Red – An exceptionally dauntless mophead hydrangea that withstands cold to zone 4 .
For Oakleaf Hydrangea:
Snow Queen ® – A democratic cold - resistant oakleaf hydrangea rated for zone 4 winters .
Alice – Zone 4 rating . bring forth an abundance of long , white flower panicles .
Snowflake ® – Compact double - flowered conformation that is very winter intrepid . honest for geographical zone 4 garden .
For Panicle Hydrangea:
Limelight – Extremely winter hardy , blooming reliably even in zone 3 . calcium oxide - green flower mature to pink or burgundy .
trivial Lime ® – A low mixed bag of Limelight rated for geographical zone 3 . Maxes out at 5 feet tall .
Little LambTM – Dwarf panicle hydrangea that withstands zone 4 winters . Grows to just 3 feet .
Be Prepared if Blooms Are Compromised
Even with the best cold tolerance ratings , monster weather issue can pass off . If your beloved hydrangeas go wrong to bloom after a round of unusually frigid temperatures , resist the urge to cut back stems in spring . Give them time to regenerate new growth from the base . With patience and proper maintenance , they should retrieve their gloriole for the following flush season .
By empathize their ideal temperature tolerances and taking protective step in winter , you’re able to persist in enjoy hydrangea in your garden for class to add up . Paying attention to flower bud hardiness will ensure the most abundant blooms each summertime . With strategic choices of planting sites and cultivars , even gardeners in parky climates can find success with these magnificent shrubs .
Can I throw a sheet or blanket over my plants?
Unfortunately , a sheet , blanket , or tarp will only keep plants safe when a short drop-off below 32 ° is expect . When it get down to the 20s , these kinds of coverings wo n’t help because there is n’t a warmth source under them to keep affair warmer . As long as you build a small nursery over each plant to heat the dirt for a few days before the temperature dropped , that might help . But most people ca n’t do that , and it would be a wastefulness of time and money .
Can’t I spray something on to protect those buds?
Although it would be expectant if spray like Wilt - pruf could protect Hydrangea buds from cold damage , there is n’t one that can .
What temperature is too cold for hydrangeas?
FAQ
Can I leave my potted hydrangea outside ?
When should I bring hydrangea inside ?
Can hydrangeas handle a freeze ?
