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Episode 64 – Hydrangeas and the 2023 Polar Vortex

Ground Breaking Banter - Rick

Around Thanksgiving, American school children are usually told that on November 11, 1620, the Pilgrims got their first look at the New World when they saw Cape Cod. After a tortuous 66-day voyage from England, the Pilgrims reached the mainland of America 400 years ago today, Nov. 11. But they didn’t land at Plymouth Rock, which is on the mainland, as the popular myth alleges: they first anchored in Provincetown Harbor at the very tip of Cape Cod. Nowadays, Cape Cod is more famous for lobster rolls and hydrangeas than Colonial origin stories, and in 2023, their legendary hydrangea displays were threatened by polar vortex that brought record-breaking lows.

One of the reasons that Cape Cod has such fabulous hydrangeas is because being surrounded by ocean leads to milder winters than the mainland – Cape Cod is considered USDA zone 7a, whereas Boston, not all that far away, is in USDA zone 6 and western Massachusetts USDA zone 5. However, in early February 2023, temperatures on Cape Cod dipped as low as 0°F, causing massive damage to the area’s abundant big leaf hydrangeas (H. macrophylla). These hydrangeas bloom on old wood, which means that during that epic cold snap, the flower buds had already formed and had to endure it like everything else. As summer came on, the lack of colorful flowers revealed the extent of the damage – and made many gardeners rethink the plants in their yard.

Listen on your favorite podcast platform or watch the YouTube video above for our whole conversation, and to find out how Cape Cod gardeners are resolving their hydrangea frustration with improved varieties like Let’s Dance Can Do

Why? Since we started Gardening Simplified fifteen months ago, we’ve covered every type of hydrangea except one: mountain hydrangea. So in this episode, I thought we’d remedy that, not just because its time is long overdue but because it’s the perfect plant for a show that’s all about hydrangea buds that can stand up to the cold. Today’s Plant on Trial is Tuff Stuff mountain hydrangea

When most people think of hydrangeas, they think of big leaf hydrangeas, Hydrangea macrophylla. This is the type with the big pink, purple, or blue flowers. The fact that it blooms on old wood leads to much confusion on the beloved shrub because, as we mentioned above, that means the plant bears its flower buds all through winter and they must withstand the challenges of the season if they are to bloom in summer. So while the plant itself is perfectly hardy – even down to USDA zone 4 – the cold tolerance of the flower buds is another story. They are probably only hardy to around USDA zone 6, though other factors come into play with that guesstimate, like how long the cold temperatures last (which was likely the issue for Cape Cod, as we discussed earlier in the show), whether there is snow cover, and when the coldest weather occurs. 

The flower buds’ inability to withstand extreme winter weather derives from their native range – coastal regions of Southeast Japan. Here, big leaf hydrangea grows near the Pacific Ocean, where conditions are generally mild, especially in winter. These regions of Japan are also mountainous, and the range of Hydrangea macrophylla extended into those areas as well. However, up in those mountains, it gets much colder than by the seaside so conditions are less favorable to flower bud survival. As a result, the plants growing up in the mountains naturally evolved better flower bud hardiness – if their flowers were constantly getting killed back, the plants would have died out. Some botanists feel that these mountain natives are significantly different enough to get their own species, and that is Hydrangea serrata, known as mountain hydrangea. 

Here at Proven Winners ColorChoice Shrubs, we recognized the potential in these plants and so have been breeding with mountain hydrangeas; Tuff Stuff hydrangea was our very first introduction. So far, there are only lacecap versions of mountain hydrangeas are available, but they are a great choice for people who have unpredictable winters or have been disappointed in the flowering of big leaf hydrangeas.

If you’d like to add Tuff Stuff mountain hydrangea – or any of the 320+ Proven Winners ColorChoice Shrubs – to your garden or landscape, you’ll find a list of local retailers here

Gardening Mail Bag - Stacey

If you have a big leaf or mountain hydrangea that’s blooming in September-December, then what you have is a reblooming, or remontant hydrangea. Reblooming hydrangeas bloom on old wood, like other big leaf hydrangeas, but they’re also able to bloom on new wood. In warm climates where the shrubs grow vigorously, those new wood flowers form quickly and you have a near continuous show for months. However, in colder climates, the plants grow more slowly and it may take well into autumn for those new wood buds to develop. If your plant experienced severe winter damage or it was cut back or your plant is stressed, you might not see any new wood flowers at all.

One of our goals here at Proven Winners ColorChoice Shrubs is to develop reblooming hydrangeas that actually rebloom. You can experience the difference in your yard with our Let’s Dance series – especially Let’s Dance Can Do and Let’s Dance Sky View

Do you have a question for us? We’re happy to help! E-mail us or use the contact tab above. Due to high volume, we may not get to your question, so if you need an answer quickly, please reach out via the Proven Winners website.

Branching News - Rick

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