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What the new zone map means for home fruit gardeners

2013 and 2023 USDA zone maps

Perhaps you’ve seen the new USDA hardiness zone map that came out this week? For the first time in eleven years, we have an updated map, and about half of the United States moved half a zone warmer (with the rest staying in the same zone they were in before). You can check your new zone here.

Before you rush out and buy tropical trees to plant in your garden, though, I thought I’d share a few thoughts from our last fifteen-plus years growing fruit.

Averages aren’t everything

Snowy gardenFirst, you need to understand what the zone map really means. It’s a thirty-year average of annual extreme low temperatures in your location.

In other words, that’s the coldest it’s likely to get in your garden on an average year — so sometimes the temperature will never drop that low and sometimes you’ll see a freak cold spell that dips even lower. In fact, as the climate changes, unusual cold waves (and heat waves) are becoming more common, so my biggest piece of advice is this:

Be conservative when picking out those fruit trees! Maybe don’t choose a fig that’s only on the edge of hardy where you’re located. Instead, if you live in zone 6b (as we now do), it’s smarter to select varieties hardy to at least zone 6a. This is especially true for fruit plants that take several years to mature.

Frost pockets

Peach flowerWhile you’re planning smart, be sure to consider microclimates. Even though the area we moved from is technically half a zone warmer than the one we’re in now (meaning we moved from zone 6b to zone 6a…which is now zone 6b!), our hilltop tends to evade early and late freezes that would have definitely struck our previous deep-valley pocket.

So no matter what the map claims, believe your eyes if they say you’re actually half a zone colder or warmer than your neighbors. And consider late freezes prone to result in fruitless years when selecting varieties — late bloomers can be a major plus.

Heat and drought

Bowl of berriesFinally, it’s worth looking at the flip side of the coin. The hardiness zone maps don’t say anything about annual high temperatures or droughts, but for many of us both of those climate concerns are increasingly relevant in our gardens.

For example, despite drip irrigation, our hilltop gets so bone dry during scorching summers that I keep losing shallow-rooted blueberry plants. I intend to move the survivors to a wetter location (which I’ll tell you about in a later post). For now, just remember that there’s a lot more to keeping fruit plants happy than making sure they evade the worst winter ice.

Shameless plug

If you want to read more of my thoughts on choosing fruit plants that will produce with minimal headache on your part, definitely check out my Weekend Homesteader: Winter ebook (or nab the full series in paperback form).

And I’d love to hear from you. How are you changing your gardening plans in response to the new maps?

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Freeze tolerance of fall crops (18 degrees Fahrenheit)

Broccoli after a hard freeze

I’ve written a lot in the past about critical temperatures of spring crops (especially flowering fruits), but I realized I don’t say much about what fall crops can handle. Usually, we’re down to the hardiest vegetables by the time we get a hard freeze. But this year, a very dry late summer meant some fall crops were running late, which was okay because we enjoyed a very long lingering autumn. Then the forecast suddenly called for the better part of a week below freezing with lows around 18 Fahrenheit, leaving me struggling to figure out what to harvest early and what to cover up. In case you’re ever in a similar situation, I thought you might like to see the results.

The image above is from the morning after the first hard freeze, broccoli I harvested early on the right and broccoli I chose to cover with a caterpillar tunnel plus row-cover fabric on the left. Everything looks pretty good, right?

Caterpillar tunnel protection vs. unprotected broccoli

Not so fast! Freeze damage usually doesn’t show up that first morning.

A couple of weeks later, the results are clearer. Uncovered broccoli pretty much bit the dust while broccoli under cover was damaged but kept growing in the warmer spell that followed. I’m not holding my breath about getting a crop from those last few plants though.

Recommendation: Harvest the broccoli early.

Winter lettuce

Elsewhere in the garden, I had two beds of lettuce, both under caterpillar tunnels plus row cover fabric. Both got nipped, but the younger lettuce (shown above) has since regrown. The older lettuce, which was starting to bolt, is now rotted down to nothing.

Recommendation: Age of the crop makes a different. Lettuce in its young prime can bounce back from a hard freeze if it’s protected but it’s probably a good idea to harvest anything that’s ready just in case.

Dewy kale

My darling kale, of course, did pretty well both under cover and in uncovered beds. Some leaves were slightly nipped; others weren’t. We’re still happily consuming a couple of meals of kale per week, often in the form of Kale Pesto.

Recommendation: Kale is our most cold-hardy fall crop if it’s moderately mature. If you’re low on row-cover, you can wait to cover this one up.

Winter hardiness of cover crops

Not that I was going to do anyting to protect my cover crops, but I thought you might like to see them after the hard freeze too. On the left — rye and vetch are thriving. Center — the oats are half-dead. Right — oilseed radishes are pretty nipped too. Of course, I wanted the oats and radishes to die and rot into the soil before spring, so this is actually good news.

Winter carrots

What about carrots? I got spooked and harvested the rest of ours because we had so many and they were so beautiful that I couldn’t bear to risk it. But our new friends from Trouivalle Farm put theirs under a version of a quick hoop and are still harvesting as needed out of the ground.

Recommendation: Be brave! Try leaving at least some carrots in the ground under row cover.

(Stay tuned for next week — we have a fascinating interview from Trouivalle Farm’s proprietors coming your way once Mark edits it into shape!)