Gardening – Page 15

Heat and Drought Come and Go

July 19, 2018/4 Comments/in Gardening/by Lee Reich

(The following is a adapted from my recent book, The Ever Curious Gardener: Using a Little Natural Science for a Much Better Garden, available through the usual outlets as well as, signed, from me at www.leereich.com/books.)

Plants’ Dilemma in Beating the Heat

Last week, with a spell of dry weather, I wrote about irrigation; then it rained. As I write, we’re experiencing searingly hot weather; thank me for the cooler weather that will surely follow.

The heat is hard on us humans, but pity plants in the heat of a hot, summer day. While I can jump into some cool water, sit in front of a fan, or at least duck into the shade, my plants are tethered in place no matter what the weather.

And don’t think plants enjoy extreme heat. High temperatures cause plants to dry out and consume stored energy faster than it can be replenished. Stress begins at about 86° Fahrenheit, with leaves beginning to cook at about 105°.

One recourse plants have in hot weather is to cool themselves by transpiring water. This loss of water from leaves can cool a plant by about 5° Fahrenheit. Over 90 percent of the water taken up by plants runs right through them, up into the air, exiting through little holes in the leaves, called stomates. Carbon dioxide and oxygen, the gases plants need to carry on photosynthesis, also pass in and out through the stomates.

All goes well provided there is enough water in the soil. If not, stomates close, transpiration and photosynthesis stop, and the plant warms. Even if the soil is moist, stomates might close in midsummer around midday if leaves begin to jettison water faster than the roots can drink it in.

So plants are put in a bind. Should they open their pores so that photosynthesis can carry on to give them energy, but risk drying out, or should they close up their pores to conserve water, but suffer lack of energy?

Beat the Heat with CAM

Enter cacti and other succulents (all cacti are succulents—that is, plants with especially fleshy leaves or stems—but not all succulents are cacti. The fleshy stems and leaves of succulents can store water for long periods. After more than a year without a drop of water, my aloe plant’s leaves still look plump and happy.

Besides being able to store water in their stems and leaves, jade plants, aloes, cacti, purslane, and other succulents have another special trick, Crassulacean Acid Metabolism (CAM), for getting out of photosynthesis of dehydration conundrum. They work the night shift, opening their pores only in darkness, when little water is lost, and latching onto carbon dioxide at night by incorporating it into malic acid, which is stored until the next day. Come daylight, the pores close up, conserving water, and malic acid comes apart to release carbon dioxide within the plant, to be used, with sunlight, to make energy.

I’ve actually tasted the result of this trick in summer by nibbling a leaf of purslane—a common weed, sometimes cultivated—at night and then another one in the afternoon. Malic acid makes the night-harvested purslane more tart than the one harvested in daylight.

C4 Beats the Heat Also

Another group of plants, called C4 plants, function efficiently at temperatures that have most other plants gasping for air and water. C4 plants capture carbon dioxide in malate, the ionic form of malic acid, which is a four-carbon molecule, rather than the three-carbon molecule by which most plants—which are “C3”— latch onto carbon. The enzyme that drives the C4 reaction is so efficient that C4 plants don’t have to keep their stomates open as much as do C3 plants. The C4 pathway also does its best work at temperatures that would eventually kill a C3 plant, and cells involved in the various steps are partitioned within the leaf for greatest efficiency.

C4 plants are indigenous to parched climates, but not uncommon visitors in gardens every- where. Corn is a C4 plant. (Cool climate grains such as wheat, rye, and oats are C3 plants.) Look- ing at my lawn, I see another C4 plant. Corn hills

Hot, dry weather in August drives Kentucky bluegrass, a C3 grass, into dormancy. Not so for crabgrass, a C4 plant, which remains happily green.

I also find some other C4 plants, in addition to corn, in my garden. As many vegetables and flowers flag, all of a sudden lambsquarters and pigweed, both C4 weeds (or vegetables, for those who like to eat them), appear as lush as spinach in spring.

Red-rooted pigweed

With a Little Help From Us Gardeners

Can we gardeners do anything to help out our plants in hot weather? Keeping the garden watered helps. Sprinkling or misting plants could keep them cool without their having to pull water up from the soil.

But the 30 gallons of water that runs up through a tomato plant in a season, or the 50 gallons that flows through a corn plant, is for more than just cooling these plants. It also carries nutrients from the soil into the plant. So it’s debatable how well a plant would grow with too much misting. And besides, wet plants are predisposed to disease.

A better alternative to sprinkling plants is to grow plants adapted to the climate and the season. Lettuce, spinach, peas, and radishes are not the plants to grow for harvest in August. At least not in full sunlight; that’s why, in midsummer, I grow lettuce in the shade beneath trellised cucumbers.

Tomatoes, cucumbers, peppers, melons, and squashes, although they are neither cacti nor C4 plants, can take the heat. And, of course, so can C4 plants like corn, purslane, and vegetable amaranth.

Thirst

July 12, 2018/13 Comments/in Gardening, Soil/by Lee Reich

Too Much or Too Little?

The current deficit of rainfall reminds me of the importance of watering — whether by hand, with a sprinkler, or drip, drip, drip via drip irrigation — in greening up a thumb.

Not that watering is definitely called for here in the “humid northeast;” historically, cultivated plants have gotten by mostly on natural rainfall. Historically, vegetable gardens also weren’t planted as intensely as they are these days. In one of my three-foot wide beds, for example, brussels sprouts plants at eighteen inches apart are flanked on one side by a row of fully grown turnips and on the other side by radishes. Five rows of onions run up and down another bed.

The rule of thumb I use for watering is that plants need the equivalent of one inch depth of water once a week.

Finger in soil to test for moisture

This approximation doesn’t take into account the fact that my bed of sweet corn is thirstier than is my bed of onions, that my plants drew less water up from the soil during a recent calm, cloudy day than they will with today’s bright sunlight and breezes, and that warmer temperatures speed water loss. Still, an inch a week is a good approximation, one very workable around here where periodic rain allow some wiggle room in watering. Not so in parts of California and similar climates that remain reliably bone dry all summer.

A sprinkler, or a hand-held hose with a spray rose for small areas, and some randomly placed straight-sided cans to catch water are an easy way to tell how long to leave the spigot on to get that inch depth of water. Hand watering Usually, about an hour, once a week, is what it takes. (That’s a long time to stand still holding a hose.) Unless it rains. Then less might be needed.

A rain gauge is an inexpensive way to know whether what seems like a soaking rain is really so. Or monitor soil moisture directly. Dig a hole, poke your finger into the soil, or, even better, purchase a “moisture meter” for less than $15; plunge the metal probe a few inches into the ground and read on the dial whether the ground down there is “dry,” “moist,” or “wet.” You want it moist.

Digital moisture probe.

Thirst Quenching a Drip at a Time

My vegetable plants get their thirst quenched with drip irrigation rather than a sprinkler. The idea of a drip system is to drip water into the soil at about the rate which plants are removing it. That doesn’t occur once a week, but every bright day, all day long.

That one inch per week rate translates to about three-quarters of a gallon per square foot. Dripline with beans My drip system is on a timer, and the time needed to apply this amount depends on the rate of flow from each emitter as well as the spacing of emitters.

After a lot of calculations and approximations (many years ago), I determined that dripping for one-half hour per day would be about right. But, as I wrote, plants drink all day long, not just once a day. My drip timer can turn on and off at three specified times per day, so the plants get their thirst quenched three times spaced out during daylight hours at ten minutes per session. My old timer offered six sessions per day; then, plants got six waterings of 5 minutes each.

Done. All I have to do is check every once in a while that all systems are go, which is one reason my drip lines run above ground. I can watch the dripping.

I do have to get out the watering can for the lettuce seedlings, the third planting of the season, that are soon to be set out, as well as for the recently planted row of carrot seeds and other recent seedings and transplants. Supplemental watering until roots of new plants stretch down into the region of the drip line’s wetting front, which spreads with the shape of an ice cream cone downward beneath each spot of dripping water.

(I’ll be leading a hands-on workshop on drip irrigation August 18th at the garden of Margaret Roach in Copake Falls. For more information, go to Margaret’s website, and type my name in the “search” box.)

Engineered Orifices

Note that I haven’t mentioned “soaker hoses.” Although the water oozes out from these porous hoses, they are not really “drip irrigation.” Sure, the water just oozes out slowly. But they’re inconsistent in output not only with water pressure and elevation, but also with time. And roots can grow inside buried soaker hoses, further muddying the water.

A real drip line has water emitters spaced six to twelve inches apart along their length, and those emitters aren’t mere holes punched in tubing. They are engineered orifices, designed to be relatively consistent in output with changes in incoming water pressure and changes in elevation along the line. They also are self-cleaning in case debris gets into the line.

And Now, A Word About Fireflies

Fun fact: Fireflies (which I knew as “lightning bugs” in my youth) are more than whimsy on a summer night; they’re also a gardener’s friend, feeding on, among other creatures, slugs.

Berries Begin

July 5, 2018/13 Comments/in Fruit, Gardening, Planning/by Lee Reich

Green Thumb Not Necessary

Every day, for some time now, my strawberry bed has yielded about five cups, or almost 2 pounds of strawberries daily. And that from a bed only ten feet long and three feet wide, with a double row of plants set a foot apart in the row. Strawberry harvest
Good yield from a strawberry bed has nothing to do with green thumbs. I just did what’s required to keep the plants happy and healthy. To whit . . .

I planted the bed last spring to replace my five-year-old bed. About five years is about how long it takes for a strawberry bed to peter out due to inroads of weeds and diseases, including some viruses whose symptoms are not all that evident.

To keep my new plants removed from any problems lurking in the old soil, I located the new bed in a different place from the old one. Further forestalling problems, plants came not from a generous neighbor and not from my old bed, but from a nursery selling “certified disease-free” plants.

I chose to grow them in a “spaced plant” system (which does not involve getting plants high, ha, ha) but allows each plant a square foot of space. Throughout the growing season, I clipped off any runners and daughter plants attempting to establish themselves and crowd into the mother plant’s space.

Other growing systems allow for runners, which makes for more economical planting of a bed but reduced initial yield. Given free rein, though, new plants eventually become the worst weed in any strawberry bed; they must be dealt with in some way.

Did I mention that the new bed, like the old one, was in the vegetable garden, where the soil is rich in nutrients and organic matter, with plants’ thirst quenched daily via drip irrigation?

In late December, when the ground had frozen about an inch deep, plants were snuggled beneath mulch as protection from winter cold. Straw, pine needles, wood shavings — any loose organic material will do.

Come spring, just as soon as plants began to awaken, I pulled back new growth beneath the mulch and tucked it under the plants’ leaves. I also trimmed off any dead leaves. The new job for the mulch was then to keep the soil moist and the soon-to-form ripening berries clean of soil.

That’s it, for all those berries, fresh picked every morning. Every morning for a little while longer, that is. I planted a “junebearing” variety of strawberry, Earliglow, known for earliness and good flavor, but bearing only for a few weeks in June. Other varieties, so called “everbearing” and ”day neutral” varieties, bear repeatedly through the season.
Netted strawberries Once Earliglow stops bearing for the season, the bed will need renovation and, through the season, its runners pinched off weekly to keep each plant “spacey.”

Better Berries

You might wonder: Why such a relatively small planting of strawberries, and why only junebearers? This admission may be sacrilege: I’m not a big fan of strawberries. I like the fruit well enough, but mostly because they are the first fresh fruit of the season.

(One other fruit does beat out strawberries as the first fruit of the season. They are honey berries, a kind of edible honeysuckle. Their flavor, thus far, has not impressed me. Breeding and cultivating honeyberries is in its infancy. They’re perhaps where apple was 2000 years ago, and the future might bring more flavorful ones.)

Back to strawberries . . . another of their deficiencies, in my view, is that you have to crawl for the fruit. And, as mentioned previously, although technically perennial, beds should replanted in a new location every 5 years or so.

The Best Berries

The fresh strawberries came on the scene on the tails of last year’s frozen blueberries, one of my favorite fruits. Perfect. (The loss of frozen blueberries is softened by the freshness of the strawberries.)

Last frozen blueberries, fresh picked strawberries

And just as the fresh strawberries fade out for the season, fresh blueberries will begin yielding this season’s bounty. Also, at the same time, black currants and red currants. And then black raspberries, and then . . . and on and on.

All You Need To Know About Blueberries

Interested in growing your own blueberries? It’s easy, if you meet their basic needs, all of which, including varieties, harvest, and other pressing questions about growing blueberries, will be covered at my upcoming BLUEBERRY GROWING WORKSHOP. The workshop will take place on my New Paltz farmden on July 22, 2018 from 9:30-11:30am, at a cost of $48. Registration is a must. For more information and registration, go to www.leereich.com/workshops.

Upcoming Blueberry Workshop

June 30, 2018/3 Comments/in Gardening/by Lee Reich

Ad for blueberry workshop

Come Visit My Farmden

June 22, 2018/7 Comments/in Gardening/by Lee Reich

This Sunday, June 24th, 2018, from 1-4:30 pm my garden/farmden is open to the public as part of the Garden Conservancy’s Open Days program. The Garden Conservancy is an American nonprofit organization founded in 1989 and dedicated to preserving exceptional gardens and landscapes. The $7 admission cost to each Open Day garden helps fund their efforts. For more information about my farmden and other local gardens open that day (and through summer), go to https://www.gardenconservancy.org/open-days/garden-directory/springtown-farmden

Playing Around With Stems

May 31, 2018/7 Comments/in Design, Fruit, Gardening/by Lee Reich

Top Doggery

My pear trees look as if a giant spider went on a drunken frolic among the branches. Rather than fine silk spun in an orderly web, strings run vertically from branch to branch and branch to ground. Yet there is method in this madness. Mine.

As I spell out in my new book, The Ever Curious Gardener: Using a Little Natural Science for a Much Better Garden, plants produce a natural hormone, called auxin, at the tips of their stems or at high points along a downward curving stems. This hormone suppresses growth of side branches along the stem, allowing growth from a bud at the stem tip or high point be the “top dog,” that is, the most vigorous shoot.

Within any plant a push and pull goes on between fruiting an stem growth. Both require energy, which the plant has to apportion between the two. The more vigorously growing a stem, the less fruitful it is.

All this talk of hormones and inherent stem vigor is more than academic; it can translate into delicious fruits.

Pear trees tend to grow very vigorously, especially in their youth, with many vertically oriented branches. A certain amount of stem growth is, of course, desirable; leaves are needed for harvesting sunlight for energy and stems are needed on which to hang fruit.

Tied branches in British orchard

But pear trees, especially in the youth, tend to put too much of their energies, too much for me, at least, into stem growth. The result is that they can take long time to settle down and begin bearing fruit.

Hence, the strings. I can change my pear trees’ habits by merely tying down branches, reducing the effect of that auxin so that growth is more uniform along a length of the stem. And, as important, slowing growth nudges the energy balance in the direction of fruiting.

Branch bending

The one branch on each young tree that I do not tie down is the main vertical stem, which is the still developing trunk off which grow the main side branches. I want this stem to keep growing upward. Also, I have to be careful not to create a downward arch when tying down any stem. You know why: a very vigorous shoot pops up from the high point in that arch.

More Fruit or More Growth?

Branch bending is not only for coaxing a tree into fruiting. On young branches, it creates a wide angle between a branch and the developing trunk. Wide angles here have been shown to result in good anchorage, sturdy side branches that can carry a weight of fruit.

Suppressing the vigor of side branches also ensures that they won’t compete with the developing trunk, which needs to be top dog.

And using string to play around with plant hormones isn’t needed on every fruit tree. At the other extreme from pear in its growth and fruiting habits is peach. Peach is naturally very fecund, and becomes naturally so at a very young age.

One reason for peach’s fecundity is that it bears all its flowers and fruits along stems that grew the previous season. Every year new stems grow that bear flowers and fruits.

Beauty, Fruit, and Fun

All this concern with auxin, vigor, and fruiting comes most prominently into play with espalier, which is the training of a tree to an orderly, often two dimensional form. The tracery of the branches themselves adds to the decorative value of the plant. Pear espalier

Fruiting espaliers, besides being decorative, produce very high quality fruit. Pruning and branch bending maintain a careful balance between yield and stem growth, and the form of the plant allows leaves and fruits to bathe in sunlight and air.

An Onion Relative and a Cabbage Relative

May 16, 2018/7 Comments/in Gardening, Vegetables/by Lee Reich

Wild Leeks, Cultivated

I got pretty excited seeing rows of scrappy, green leaves emerging from the ground between a couple of my pawpaw trees. The leaves were those of ramps (Allium tricoccum, also commonly known as wild leeks) that I had first planted there two years ago, with an additional planting last year. Ramps

There’s no reason that ramps shouldn’t thrive here on the farmden; they’re native from Canada down to North Carolina and from the east coast as far west as Missouri. They’ve been best known in the southern Appalachian region, where festivals have long been held to celebrate the harvest.

Ramps became more widely known in the 1990s when, with the publication of a ramp recipe in Martha Stewart Living Magazine, the wilding became a foodie-food. Ramps are now threatened with being over harvested. Which, along with a desire to have this fresh-picked delicacy near the kitchen door, is the reason I planted them.

Large patches of ground in a forest preserve in New Jersey near to where a friend lives are blanketed each April with ramp greenery. We had dug up a few — very few — of the ramps, leaves and bulbs, which I transplanted here. Our harvest was not a threat to the ramp population. No one else has ever been seen harvesting there, and we dug up less than 1% of what was there. Research has shown that harvests are sustainable if no more than a different 5-10% of a planting are harvested yearly.

In the wild, ramps thrive in damp soil rich in organic matter in the shade of deciduous trees. My pawpaws provide the deciduous shade. The ground beneath those trees has been enriched each year for 20 years with a thick mulch of autumn leaves. To give the ground a further boost as far as organic matter and nutrients, I lay down a couple of inch thick blanket of compost over the bed last summer.

Over time, the bulbs should multiply and the plants further spread by self-seeding. I plan to harvest some seeds when they ripen in late summer to grow the seedlings under more controlled conditions.

The seeds have a double dormancy so they often don’t sprout until the second spring after ripening. The root dormancy, the result of immature embryos, is overcome with warmth and moisture. A warm autumn might be sufficient; if not, the next growing season. I plan to hurry the process along by potting up the seeds and keeping them warm (about 70°F) and moist for a couple of months. Then I’ll whisk the pot into the refrigerator to overcome the shoot dormancy, which requires a couple of months of cool, moist conditions, to jolt them awake. (More about natural blocks to seed germination in my new book The Ever Curious Gardener: Using a Little Natural Science for a Lot Better Garden.) The seedlings, as might be expected given their natural habitat, grow best with some shade — 30% shade to be exact, according to research.

Ramps are among the few perennial vegetables I grow. They are spring ephemerals, so in just a few weeks, their leaves will dissolve into the ground as the plants go dormant, to return again each spring for my dining pleasure.

A Different “Kale”

Seakale (Crambe maritima) is yet another perennial vegetable that I grow. It’s a cabbage relative that just now is sending up sprouts from its thickened roots. As soon as I noticed the sprouts, I covered the plants with an overturned, clay flowerpot, covering the drainage hole with a saucer to prevent light from reaching the plant.

Seakale tastes best blanched, that is, with its shoots grown in darkness. Under such conditions, leaves stretch out and grow pale and tender. In light, the taste of the leaves is too sharp. Or so I’ve read: Although I’ve grown seakale for many years, I wanted the roots to build up enough energy reserves to fuel new growth in the dark. This year, I will taste seakale.

Seakale will continue to earn a place in my garden even if its flavor falls flat (or sharp) because it’s a beautiful plant. Once released from the dark, new leaves emerge silvery green, large, and wavy. And then, later on in summer, foaming sprays of small white flowers emerge from within the whorl of leaves.

Expect a report on my take of seakale flavor in a couple of weeks, which is the time required for blanching. Like other perennial vegetables, once the harvest period ends, plants need to grow unfettered for the rest of summer to replenish the stored energy they spent fueling spring growth.

Spring?

May 11, 2018/11 Comments/in Gardening/by Lee Reich

Spring, You’re Late

Seems like everyone — in the northern half of the country east of the Rockies, at least — is talking about this spring’s weather. Robert Frost (in “Two Tramps in Mud Time”) had it right when he wrote:

The sun was warm but the wind was chill.
You know how it is with an April day
When the sun is out and the wind is still,
You’re one month on in the middle of May.
But if you so much as dare to speak,
A cloud comes over the sunlit arch,
A wind comes off a frozen peak,
And you’re two months back in the middle of March.”

Perhaps T. S. Elliot (in “The Waste Land”) was right in writing that “April is the cruelest month.”

But has this past April really been crueler than most? Usually I pooh-pooh day to day impressions. But even Sammy, who usually bounds over to me from his doghouse each morning when he sees me, stayed in and watched as I crossed the yard a couple of weeks ago over ground recently covered with a dusting of snow. Sammy, the dog, and snow

Phenology, the study of climate as reflected in the natural cycles of plants and animals, is one way to give the weather an objective assessment. For decades, I’ve recorded the dates on which various plants have blossomed. My interest was horticultural: In spring, plants blossom after experiencing a certain accumulation of warm temperatures. So various blossoms can be indicators of when it’s safe to sow seeds or set out plants of various vegetables and flowers.

Depending on late winter and spring weather, blossoming dates for various plants can vary quite a bit. Microclimate also plays a role, so I’ve tried to always note blossoming on the same plant from year to year. Back in 2010, forsythia bloomed about April 1st, the earliest I’ve ever recorded. Contrast that with 2009, when it bloomed about April 15th, or back in 1984, when it bloomed on April 25th!

This year, forsythia bloomed on April 23rd, late again. Over the years, forsythia bloom dates average around the middle of April, so this year is definitely late. All these forsythia bloom dates are for forsythia on my farmden, which is in a local cold pocket so blossoms spread their yellow petals a few days later than plants even just a few miles away.

Another key indicator for me is cornelian cherry (Cornus mas), whose yellow blossoms are most welcome because they frequently open the first day of spring. Not this year though; mine bloomed on April 20th.

Daffodils typically bloom here in early April, although back in 2016, they bloomed on March 25th. This year, April 21st.

One of my favorite blooming shrubs, also producing very tasty fruit, is Nanking cherry (Prunus tomentosa).

Nanking cherry hedge

Stems on the row of them along my driveway typically form a veritable wave of pinkish white blossoms around the middle of April. As I write, it’s April 24th and that wave is just building. If warm weather continues, it should roll in within a few days. (Update: It did, on the 28th.)

Plants Tell Me When To Plant

It’s tradition to plant corn when “oak leaves are the size of mouse ears.” Considering phenology, I take timing one step further, planting, for example, lettuce seeds

Setting out onion transplants

when forsythias blossom, cabbage transplants when apples blossom, and — this is a tough one — peas a week BEFORE forsythias blossom.

So yes, it has been a “cruel” spring, if you’re wanting some warmth and sun. Then again, this cool weather has retarded, so far at least, blossom development of my fruit trees, which is a good thing. The later these trees blossom, the less chance for the open flowers to be burned by subsequent frosts.

Peas, Where Are You?

The downside to this atypically cool spring weather is that it has delayed planting of annual vegetables and flowers, or their growth if they’s already been planted. I sowed peas, as I always do, on April 1st. Still no sign of the poking up through the ground. I’m going to go outside, scratch around in one of the pea rows, and check if the seeds have either sprouted or rotted.

I’m back. The peas are okay, their first bits of green are peeking up through the surface of the ground.

No matter if the season is unseasonably cool or warm, by this time of year the progression of blossoms provides a feast for the eyes and the nose.

Plant sale in June . . .

May 6, 2018/2 Comments/in Gardening/by Lee Reich

Plant sale web ad, 2018

(Micro)climate Change

May 3, 2018/3 Comments/in Fruit, Gardening, Planning/by Lee Reich

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. Microclimate, early tulips 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. Microclimate, lingering snow 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. Apple blossoms 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!!