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Episode 66 – The new USDA zone map, and what it means for you

Ground Breaking Banter - Stacey

We’re switching places for today’s episode in light of what might be the biggest possible breaking news for gardeners: the USDA put out a new hardiness zone map on November 15, 2023. Because this new map is based on data over the last thirty years, collected from nearly double the number of weather stations as the previous one, and incorporates GIS technology, it is a better reflection of the conditions we garden in. Join us on your favorite podcast platform or at the YouTube link above for the full discussion of why the 2023 map is not causing nearly the stir that the 2012 map did, why the USDA hardiness zone system has a major shortcoming, and why the last two maps have further divided hardiness zones into a and b areas.

Check here to see if your hardiness zone changed in the 2023 map

You can watch the video that we referenced in this segment on our YouTube channel

As Rick picks this week’s Plant on Trial, he takes the opportunity to cover one of this favorites – vitex, also known as chaste tree. He loves its flowers and the aroma of its foliage, reminiscent of Vick’s Vapo-Rub, but it’s also the perfect plant to talk about on the topic of USDA hardiness zone changes. Listen in on our whole conversation to find out why Rick loves vitex!

If you’d like to add Blue Diddley vitex – 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

This is a bit of a tough question, as I’m not sure there’s just one answer. But to start with, make sure your plant isn’t grafted. Maples are sometimes grafted to get a faster growth rate or increase hardiness, and if your paperbark maple is grafted, cutting it back severely could cause what is likely a far less impressive understock plant to take over. Look for a line or slight ridge around the base of the plant, or a distinct difference between the top and lower part. If your plant is not grafted, then my recommendation would be to allow it to grow as-is for another year or two to build up a more robust root system. Then cut it back – the bigger that root system is, the more growth will result from being cut back. You also might need to cut it back more to encourage more growth to break. It’s definitely a tough call, and there are no guarantees, though both Rick and I agree – a multi-stemmed paperbark maple is gorgeous!

A small tree seedling with one branch to the right. A small paperbark maple seedling tree with one branch to the left and a human hand for scale.

Panicle hydrangeas sometimes put out this wild “broomstick growth,” and I’m not entirely sure why. It could also be related to the effect of being pruned hard and a robust root system fueling a bunch of growth…but this ability of panicle hydrangeas to grow like this is why they are able to be offered as standards, or tree-form, plants. As we mention in the show, plants have a characteristic known as apical dominance: the top-most bud produces hormones that suppresses the growth of lower buds, so if you cut back the broomstick growth, it should release lower buds and help the plant fill in. You can cut those tall stems back as much as you’d like to achieve the look you want.

A dormant panicle hydrangea with very straight, tall stems growing out its center.

The answer to this depends entirely on which hydrangeas you have. Debbie has smooth hydrangeas, H. arborescens, which bloom on new wood – that means they are not bearing flower buds during the winter, so if they are cut back – by deer or humans – it won’t negatively impact flowering next year. So spraying this type of hydrangea isn’t strictly necessary through winter, though I definitely would in late February-early April, when the deer will be especially hungry and seeking out additional food sources. If you had a hydrangea that blooms on old wood, like big leaf, mountain, or oakleaf, then applying deer repellent regularly through winter and spring would be absolutely imperative in order to preserve the blooms. 

A line of hydrangeas growing under a high canopy of trees and surrounded by pine needles. Three hydrangeas with white flowers blooming in a bed mulched with pine needles.

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

The National Christmas tree was no match for Washington’s gusty weather Tuesday November 28, toppling over at one point because of high winds.
The tree – a 40-foot Norway spruce – was installed on the Ellipse in November, according to a news release from the National Park Service.

LAINGSBURG, Mich. (WILX/Gray News) – Deer feasting on pines and spruce means the holiday tradition of cutting down a Christmas tree gets the axe this year at a tree farm in Michigan.

HOW ARE AMERICANS BEING ECO-CONSCIOUS THIS HOLIDAY SEASON:

Reuse decorations from previous years — 45%
Use reusable dishes (vs. single-use plastic) — 35%
Avoid overconsumption on Black Friday and Cyber Monday — 30%
Coordinate with (other) guests to avoid having too much food — 27%
Make homemade gifts — 26%
Buy more locally sourced ingredients — 24%
Compost any food scraps/uneaten leftovers — 18%
Shop with eco-conscious retailers — 15%
Offset any holiday travel — 13%
Serve more meatless options — 12%

A giant tumbleweed roughly the size of a Volkswagen beetle was spotted hurtling its way down a four-lane road in California.

Australia has too many sheep – and farmers are giving them away for free.

Drought? In this age of water wise gardening check this out: Slick City, a new “waterless water park” just opened in Houston.

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Pink rose of Sharon flowers bloom on a plant with variegated foliage.

Episode 92 – Weeding by Example

Ah, weeds – maybe the #1 thing that discourages people from gardening. But weeds are interesting and become a lot easier to manage when you apply some basic IPM principles. Featured shrub: Sugar Tip rose of Sharon.

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