Zone 6 zone denial tip: standard hybrid gladioli are reliably hardy only to zone 9 - or 8b, maybe - but if you have well drained soil, plant them 5 or 6 inches deep and mulch heavily in fall (in this case before the ground freezes), there’s a good chance they’ll come back.

By now you’ve probably gotten the word: the long awaited, massively updated USDA Climate Zone map, the first revision since 1990, has finally arrived. And  – insert giant snarky “this is news?” – it shows large swaths of the country have moved up at least a half zone.

In 1991, when I got together with Bill and began gardening in the Hudson Valley, I could joke that my new life didn’t net me a single climate zone, even though the NY garden is about 300 miles southwest of the one in Maine. Until a couple of weeks ago, they were both in zone 5b. Now, while New York remains 5b – by the skin of its teeth, from the looks of things – Maine has been promoted to 6a.

Of course the difference between the two may well be less than the full 5 degrees between half zones. Same with the big chunk of Nebraska that’s now 5a instead of 4b. It’s also possible that Chicago, a heat island, may have remained exactly the same while getting a higher zone assignment because of better measurement.

But whatever the physical changes, most of the numbers did go up. The USDA, however, refuses to draw what appear to be obvious conclusions.

Perhaps not surprisingly, there has been a lot of flapdoodle* about how the zone changes are strong proof of global warming and the USDA is simply stonewalling. There has also been a fair amount of wishful thinking along the lines of “I thought it wouldn’t be hardy here, but now I know I can grow it. Yay!”

Well, yes and no. USDA representative Kim Kaplan doth perhaps protest too much when insisting that the new map differs so fundamentally from the old that the two cannot be compared. Given the unanimity of projections of increasing warmth in future, it could be quibbling to maintain that the 30 years of data behind the new map is weather, not climate, because climate measures brackets of at least 50 years. And when it comes to wishful thinking, no one with any gardening knowledge would deny that plant hardiness is indeed an increasingly mobile target.

But all that said, I don’t think it would hurt to calm down a little and stop making the poor map carry far more weight than it should. On the first count, there are a lot more robust proofs of global warming (check out this government sanctioned analysis of trends in the Southeast, for instance, if you really want to have your pants scared off.) On the second count, it pays to remember that average winter lows – the only thing measured on the map – are by no means the single factor influencing plant survival; and when it comes to climate change the challenges far outweigh the benefits, even at the home garden level.

Some Factors Other Than the Thermometer That Influence Winter Survival of Plants

Time to harden off. When cold comes gradually, plants have a chance to toughen up in preparation for winter. When cold comes suddenly, plants may be killed by temperatures they could otherwise sail through unscathed.

Duration of the coldest temperatures. A plant rated hardy to -10 is more likely to survive a few hours of -15 than ten straight days of -5.

Winter soil moisture. Dry climate plants from lavender to cactus care a lot more about drainage than they do about air temperature.

Yearly rainfall. Seattle and Tucson have the same zone number but are not otherwise similar. Moisture needers and drought needers alike will go into winter deeply stressed if grown in the wrong place, and that weakness can finish them off when deep cold is added.

Late summer and fall care. Nitrogen fertilizer spurs tender growth that’s vulnerable to winter kill. Late pruning does the same thing.

Snow cover. A deep fluffy blanket of snow that lasts all winter will protect plants (especially perennials) from cold that would kill them if the ground were bare.

Some Gardeners’ Problems Headed This Way As a Result of Climate Change

Rapid temperature swings. A long mild fall followed by a plunge into the deep freeze, and/or a very early spring, followed by a plunge into the deep freeze.

Extreme weather events. Extended droughts, torrential rains, hurricane force winds.

Shorter winters. Plants like apples, peonies and lilacs that must have a long winter sleep can languish with too little rest. Insects and diseases once kept in check by extended cold will have higher rates of survival.

Less reliable snow cover, more frequent ice storms. Snow protects; ice kills.

Hotter summers. Northerners will have better luck with heat-loving annuals from tomatoes to moonflowers. Southerners may well have less; too much heat prevents fruit set and pushes annual flowers into early graves. The region of happiness for plants that must have cool nights even in summer (peas, delphiniums, rhododendrons, sugar maples) is headed toward Canada.

A Few Coping Strategies may be found here.

* Some back story on the flap.

Whatever its limitations, the USDA hardiness zone map has long been a widely recognized metric. Breeders and nurseries use it to rate and label plants. Scientists use it (along with a lot else) when investigating things like the spread of invasive weeds. The USDA itself uses the map to set some crop insurance standards.

Not chopped liver; and by the time the century turned, it was clear to all that the 1990 map was both insufficient and inaccurate. The USDA commissioned a new one from the American Horticultural Society, which had produced zone maps before. Projected appearance date was 2003.

But then the map didn’t show up – or rather it didn’t show up for long. As I remember it, there was a new version on the AHS website, but only very briefly. The curious were told it went away because it was just a draft; the USDA was not satisfied, and revisions were under way.

This was the party line for quite a while. During this while, we were enjoying the G.W. Bush administration, increasingly notorious for its disinclination to confront man made climate change. People began to think dark thoughts.

These thoughts were not brightened when, in 2006,  the Arbor Day Foundation published an updated zone map of its own, using some (but not all) of the same data as the rejected AHS draft. The ADF website provides an animation of the old map morphing into the (ADF) new one. It is not reassuring.

More grumbling. More Bush administration. More delays, now routinely attributed to the difficulty of producing a sufficiently sophisticated, web friendly interactive map.

Not so fast forward to January 25th, 2012. The new map is introduced at the National Arboretum. Distant journalists are invited to attend via webinar. I attend.

Neato! The thing is terrific. It really IS a great leap forward – for doing what it’s supposed to do, anyway. One need only enter a zip code to get the corresponding zone assignment, and there is a lot of other information there for the drilling down.

The introduction ceremony concludes with a question period. Various reporters ask questions. The most vocal questioners do not appear to be gardeners and what they really, really want to know is why the long suffering Ms. Kaplan, who has been fielding these enquiries ever since the flap began, will not knuckle under and admit that the map proves global warming is undoubtedly here. She won’t do it. (Her reasons are detailed on the map site, under “what’s new?”)

So, official word is still that the map was not delayed  - perhaps by underfunding? –  during the previous administration, which may or may not be true. But in fairness, nobody’s trumpeting its appearance as the return of sanity, either. So at the very least the USDA is an equal opportunity sphinx.

But our part of the Hudson Valley is still zone 5b, though teetering on the edge of 6, and figs are not hardy north of zone 7.  So what makes me think we can pull this off?  Pure hubris? My usual oversupply of sunny optimism ? Too much research into fig protection during the Times Q&A days?

Some of each, I have no doubt. But the main reason to give it a try is this house’s uniquely suitable spot, a double protected corner facing southwest.

The fig in late September, slightly taller than 5 feet, planted as close as possible to a very cosy corner.

If you count the fact that the house ( circa 1870) is not exactly a model of tightness, the protection is triple. But double is the important part; the corner has extra backup because the house sides don’t meet.

There’s an airshaft back there on the left, a 2 foot square tube from ground to third story with the outside of a brick chimney on its north side. The chimney is lined, so it doesn’t get heat from within, but it does soak up the sun.

This monstrosity was created when previous owners expanded a bay window into a two story box. Or maybe the box was already there and the airshaft came into being when the almost-adjacent porch was closed in to become a sunroom.

The verbena (temporarily) in the living room bay

If you look out the left window you’ll notice the west wall of the kitchen is – how shall I put this – rather closer than would be suggested by good design. When the kitchen was still a sunporch it had a window right across from this one, but because the sunporch walls and ceiling were clad in dark brown wainscotting and there was a dark brown rug on the floor…but I digress.

Bill’s grandfather in western Pennsylvania went with the trench method: dig a trench right next to the fig, just big enough to hold the trunk and gently-bent branches. Cut just enough of the roots to permit tipping the tree into the trench. Wrap it into a bundle with burlap or porous landscape fabric. Tuck it in. Surround it with leaves or straw. Cover the fig grave with burlap or landscape fabric and bury it under a large heap of  leaves or straw, extending the heap well beyond the trench edges ( making the heap tall enough will automatically extend it). Cover the heap with a waterproof tarp.

Bill feels this is the best way to go, and as he is willing to do the digging far be it from me to say no.

Yet I’m also sort of wedded to my original plan:  wrap the fig with several layers of bubble wrap, leaving the top partly open to provide ventilation, then wall off the corner with heavy plastic and then fill the entire enclosure with straw and/or leaves, layering in a few twiggy branches to keep the material from matting down unduly when wet. Brooklyn’s Italian (and formerly Italian) neighborhoods are rich with variations on this theme; when you see fat columns of burlap with straw sticking out they’ve probably got a fig tree in there somewhere.

On the good side, the wrap method would prevent shock from root-pruning and could be undone slowly in stages as the spring warmed up. On the bad, it’s probably even more work than digging a trench in the stony ground – especially given that somebody else would dig the trench.

It’s kind of a tossup for ugly – either a wall of plastic only visible  from the side yard or a gravelike hump right under the window.

Fortunately, we still have time to dither, and this is the only fig that still requires protection. The other five are now safely in pots in the cellar.

How did that happen, you are entitled to wonder. Rolling River Nursery, 17 choices on the fig page, very nice people and very good root systems, too. When the Chicago arrived in May it was a 30 inch stick with a tiny shoot at the bottom.

And like its buddies it got as far as figs before the frost nailed it.

Kind of amazing considering it had nothing but cold and damp for half of its first growing season. Welcome to the Northeast, little fig, acclimate or die.

Note, 11/08/09: In the end we went with the trench. The instructions for doing so have been updated to briefly describe what we actually did. A full set of instructions will be provided after we know that it worked.

it's all one vine, base at lower right

But it’s also brought us a great deal of aggravation. Moving large plants back and forth between the Maine coast and the Hudson Valley is not my favorite thing.  

So wouldn’t it be great to have a passionflower that was willing to live outdoors? YES! Passionflowers are almost all denizens of zones 9 and south, but there is one, the native Passiflora incarnata, rated hardy to Zone 6 or 7 – and we are almost 6.

Passiflora incarnata, aka Maypop

P. incarnata’s common name, Maypop, supposedly comes from the way it springs up suddenly very late in spring – a clue that it’s happiest in warmer climates (nothing late about May around here).

The two healthy vines that came last April were therefore given choice cosy spots: right next to the house facing East, with plenty of light from the South.

No matter. They sat and sulked for months, remaining the same 18 inches tall well into July. Then whammo!  In the space of about 2 weeks they were halfway up their trellises, sporting multiple shoots and even a few buds. And that’s when I learned about the ants. Big black stinging ants love maypops; they were all over the vines and very aggressive about defending their territory.

reach for that bud at your peril

 There HAD been a lot of insect warnings, just not about the ants. Maypops are frequently chewed to shreds by the caterpillars of the Gulf Fritillary, Agraulis vanillae.

Agraulis vanillae, the Gulf Fritillary, photo by Peter J. Bryant

utterly gorgeous underneath.

Agraulis vanillae, photo by Peter J. Bryant

Making the caterpillar damage definitely something worth putting up with – except that there was never a sign of anything lepidopterous.

Might be we’re too far north, the Gulf Fritillary page where I found Dr. Bryant’s photos describes it as a tropical species and the map at Butterfliesandmoths.org, which does show it venturing quite a bit northward, does not record any sightings in New York.

IF (big if) the vine comes back for a few years the butterfly situation may improve, but I’m afraid there’s also a chance that the deck is stacked against. Even if the ants don’t get ‘em, the caterpillars are probably no match for our September surprise.

praying mantis on the maypop trellis

She stayed around for several weeks, laying eggs I hope.

Warning Note for Southern Readers: P. incarnata may be native, but that doesn’t mean it’s completely benign. Where not kept in check by mown lawn, asphalt (or, possibly, infestations of A. vanillae) maypop can run near-amok… and be nearly impossible to eradicate.