(Micro)climate Change
As the train rolled southbound along the east bank of the Hudson River, I took in the varied landscapes along the opposite west bank. Spilling down the slope to the river on that bank at one point was what appeared, from a distance, to be a vineyard. I was envious.
(I never could understand why the region here is called the Hudson Valley. Along much of the Hudson, the land rises steeply right up from river’s edge. Where’s the valley?)
I wasn’t envious of the riverfront site of the vineyard property. I wasn’t even envious of having a whole vineyard of grapes. (I cultivate about a dozen vines.)
What I did envy was the microclimate of the site. Microclimates are pockets of air and soil that are colder, warmer, more or less windy, even more or less humid than the general climate, due to such influences as slopes, walls, and pavement.
The vineyard was not that far from my home, but the microclimate was worlds apart. Every parcel of land, from a forty-acre farm field to a quarter acre lot, will have some microclimates, and siting plants with this in mind can spell the difference between whether or not they thrive or even survive. 
I’m banking, for instance, on the slightly warmer temperatures near the wall of my house to get my stewartia tree, which is borderline hardy here, through our winters. (It has.) And I expect spring to arrive early each year, with a colorful blaze of tulips, in the bed pressed up against the south side of my house. Proximity to paving also warms things up a bit.
Microclimate for cold, microclimate for warmth
Microclimate isn’t always about trying to keep a plant warmer in winter, or speeding up growth in spring. It’s also useful for keeping plants cooler. By training my hardy kiwifruit (Actinidia spp.) vines right up against the shaded, north sides of their hefty supports, I keep the sun off their trunks in winter and avoid the splitting that occurs when trunks are warmed during winter days, then precipitously cooled as the winter sun drops below the horizon. 
By planting the coveted blue poppy in a bed on the east side of my house, I hoped to give the plant the summer coolness that it demands. (That east bed was still too sultry; the plants collapsed, dead.)
Microclimates are important when growing fruit plants that blossom early in the season because frozen blossoms do not go on to become fruits. Early season bloomers need microclimates that are slow to warm up.
South facing slopes stare full face at the sun, so these slopes warm up early in spring and are warmer in both summer and winter. Therefore, a south facing slope—even if the grade is only slight—can be used to hasten fruit ripening on a plant like persimmon, which blooms late but needs a long season when grown near its northern limits.
Right after I push soil over the first seeds of sweet corn that I plant, I firm it over that hole with my foot at an angle to make a south-facing depression in the ground. That mini-slope will warm up just a wee bit sooner than flat ground.
The sun glances off north slopes, delaying their warming in spring and keeping them cooler in summer. Such a microclimate is ideal for an early blooming fruit tree like apricot or peach, and for plants, such as sweet peas, that enjoy cool summer weather. Likewise ideal for such plants is near the north side of a building, where shade remains through winter and the early part of the growing season.
If a slope actually has some elevation to it, the air is going to cool by one degree Fahrenheit every three-hundred feet going up the slope. If I had sloping ground, which I don’t, and sought a cooler location for planting, I’d avoid planting at the very top of the slope, though, because the upper reaches are usually windy.
A cold spot, here
Ideal vineyard site, from plant perspective, in Germany
Counterintuitively, the very bottom of a slope will also be a cooler microclimate. On nights when the sky is clear, with no clouds or leafy trees to block re-radiation of the sun’s heat from the ground back to the heavens, the air at ground level cools. An “inversion” occurs, with warmer air higher up. The cold air, which is denser than warm air, flows downhill to settle into depressions, just as a liquid flows downhill. A low point would be the worst possible location for planting strawberries, which grow near ground level and whose early blossoms are threatened by late frosts in spring. Any dense fence or shrubbery on a slope stops the downward flow of cold air, which will pool, just as dammed water would, near the upper side of the barrier.
Among the fruits I grow are apples, peaches, plums, and pears, all of which tend to bloom early. My site, unfortunately, is just about the worst possible site for growing these fruits. 
The cold air that settles here on clear spring nights increases the likelihood of late frosts and also causes moisture to condense on the plants, leaving them more susceptible to disease. Hence my envy for that sloping vineyard site.
Check out my new book, The Ever Curious Gardener, for more on microclimate!!
Doing Good with Saw and Lopper
Fruitful Pruning
To begin, I gave the bush in front of me a once over, eyeing it from top to bottom and assuring it that the next few minutes would be all to its good. It was time for my blueberries’ annual pruning, the goals of which were to keep them youthful (the stems, at least), fecund, and healthy.
Blueberries galore
I peered in at the base of the plant, eyeing now the thickest stems. Blueberry bushes bear best on stems up to 6 years old, so the next move was to lop or saw any of these stems — usually only 3 or 4 of them, more on a neglected plant — as low as possible.
Sammy & me, pruning blueberries
To keep track of the ages of individual stems, I mark off the age of them each year with a Sharpie. Just kidding! The thickest ones are the oldest ones, and 6-year-old stems are generally an inch or more in diameter on healthy bushes.
Removing those stems that are over the hill frees up space for younger stems to develop. Each year blueberry bushes send up new sprouts from ground level, usually a few too many of them. They need to be thinned out so they don’t crowd each other as they age. I leave a half dozen or so of the most vigorous new sprouts, lopping all others to the ground.
That’s pretty much all there is to pruning a blueberry bush. With the very oldest and some of the very youngest stems cut to the ground, the bulk of pruning the bush is finished.
Blueberry bush, before & after pruning
I’ll also snip off any dead stems, remove a branch here and there where they are congested, and shorten any stems that will arch to the ground when laden with fruit.
That’s it. Finished, except to step back and admire my handiwork.
And Now, For Other Shrubs
The same pruning done on blueberry could, in essence, be applied to lilac,
forsythia, mockorange, hydrangea, and any other informal shrub. This technique is known as rejuvenation pruning because, over time, the above ground portion of the shrub is annually rejuvenated. In the case of blueberry, the roots live unfettered year after year but the bush never sports stems more than 6 years old. A perennially youthful blueberry bush can go on like this, bearing well, for decades like this.
Not all shrubs perform best on stems up to 6 years old. Some, such as kerria, snowberry, rambling roses, and summer-bearing raspberries perform best on 1-year-old stems. So every year those 1-year-old stems are lopped to the ground and the youngest stems are thinned out.
Some shrubs, such as butterfly bush, everbearing raspberries, and red twigged dogwood, perform best on new stems. In this case, the whole plant gets lopped to ground level each year. (Everbearing raspberries actually bear on both new stems and on 1-year-old stems, so could be pruned as in the previous paragraph. That takes more time but does yield a midsummer crop on the 1-year-old stems and a late summer and fall crop on the new stems.)
At the other end of the spectrum in shrub pruning are witch hazel, tree peony
, rose-of-sharon, climbing roses, and flowering quince. These shrubs are among those that perform well year after year on the same old, and always growing older, stems. They also grow few or no suckers each year. The upshot is that thesis shrubs are the easiest to prune: Don’t.
I detail the ages of stems that are “keepers” for every shrub, plus other details in pruning all kinds of plants, in my book The Pruning Book.
Getting Formal
All this pruning refers to informal shrubs. For formal shrubs, such as the privet hedge near one edge of my yard, I put aside the lopper, pruning shears, and pruning saw, and get out the hedge trimmer. Shearing all the youngest twigs, working, this time, higher in the bushes rather than down near ground level, elicits repeated branching which results in dense growth.
To keep this formal hedge clothed from head to toe in leaves, I keep the row of plants narrower towards their upper portions. This lets sunlight beam down on the shrubs from top to bottom.
Northern Figs? Yes!
Faking The Subtropics
At first blush, the setting would not seem right for fig trees. There they were, in pots sitting on my terrace — so far so good — but with snow on the ground around them. Figs? Snow?
Figs seem so tropical but, in fact, are subtropical plants. And it does sometimes snow in subtropical regions. Climatewise, subtropics are defined as regions with mean temperatures greater than 50 °F with at least one month below about 64 °F. Further definitions exist but the point is that it does occasionally snow in subtropical regions; temperatures just never get very cold.
My potted figs couldn’t have survived our winters outdoors. They wintered in my basement, where winter temperatures are in the 40s. Cool temperatures are a must to keep the stored plants from waking up too early indoors, then, because the weather is too cold to move them outdoors, sprouting pale, sappy shoots in poor indoor light. Even sunny windows don’t hold a candle (pardon the pun) to sun in the great outdoors.
Sleep, Sweet Figs
My goal is to keep the plants asleep as long as possible and then to move them outdoors just as soon as temperatures are unlikely to plummet low enough to do them harm. I figure that date was yesterday, April 2nd. Most fig varieties tolerate cold down into the 20s, some even lower.
Roots of all plants have evolved in, of course, the ground, where temperatures are more moderate than the air. So they can’t tolerate as much cold as can stems. With cold penetrating the exposed soil in pots, more so the smaller the pot, I have to keep an eye on the outdoor temperature and, if it gets too low, whisk all the pots into the shelter of the garage.
In the ideal world, temperatures will slowly warm without any dramatic lows or highs, and fig buds will gradually unfold into shoots along whose length will develop and then ripen juicy, sweet Celeste, Genoa, Excel, Ronde de Bordeaux, and Rabbi Samuel figs.
Cold concerns this time of year don’t apply to one of my potted figs, a Himalayan fig (Ficus palmata). I rooted a cutting of this plant a few years ago. It’s billed as being much more tolerant of both cold and summer rain than common figs (F. carica), both assets for a fig in this part of the world. I have yet to see fruit from this plant.
Primal Urges?
What is it about figs that makes so many people want to grow them? I know of someone in Sweden who grows them. Even someone in Canada who has a collection of over 200 varieties (www.adrianosfigs.com)! Figs are an ancient fruit with origins in the Fertile Crescent, so is it some primal connection with the distant past that is the attraction?
A big part of the attraction is, of course the flavor of fresh figs, which is unlike that of the dried fruit. Market figs don’t make the grade because figs have to be picked dead ripe for best flavor, at which point they’re too delicate to travel much further than arm’s length from plant to mouth.
As would be expected of so ancient a fruit, hundreds of varieties exist — and perhaps thousands of names because more than one name has been ascribed to many varieties. My variety Rabbi Samuel, for instance, mentioned above, is, I know a made-up name. 
A friend made it up because he got it from some Hassidic Jews who had no name for it. And the frequently grown variety Brown Turkey is a name assigned to two different varieties, one more common on the west coast and the other more common on the east coast. And the east coast variety has a number of other names, including Everbearing, Texas Everbearing, and La Perpetuelle.
The first plant I ever grew once I got the gardening bug (in my 20s) was, in fact, Lee’s Perpetual (another name for eastern Brown Turkey). I grew it in a pot in a not very sunny window of the apartment I was renting. Not surprisingly, in retrospect, the plant never fruited.
Nowadays I think of the climate in which figs are native when growing my figs: cool, moist winters (as in my basement) and hot summers with plants baking in abundant sunlight. I now harvest plenty of figs.
Postscript April 6th: Temperatures of 22 °F perhaps prompted me awake at 3 am; I got up and lugged all 11 potted figs into the shelter of my unheated garage.
