New York Grown Oranges!

Yes, A True Citrus

Oranges? In New York, planted outdoors in the ground? Yes, I have them ripening on the branches now. No matter if they ripen thoroughly or not because, although they are true oranges, delicious flavor  is not one of their assets. It’s still a plant well worth growing.

The plant is the aptly named “hardy orange,” actually a true citrus species, Citrus trifoliata. (Previously, hardy orange was a citrus relative; botanists recently moved it to the Citrus genus from the closely related Poncirus genus.)
Hardy oranges ripening

Mostly I planted hardy orange for its stems, whose show is at the same time intimidating, interesting, and decorative. Stems of the variety that I grow, Flying Dragon, twist and contort every which way, and then add to the show with large, recurving thorns. Stems and thorns are forest green, even as they age, and remain so all through winter to make the plant especially decorative when leafless.Bare stems of hardy orange

I would have planted Flying Dragon hardy orange just for its stems. But adding to the show, in spring are white flowers — citrus flowers — that are fragrant just like those of oranges and lemons. On my plant, at least, they’re smaller with commensurately less fragrance.

This year, this month, Flying Dragon has presented yet another attractive face. Its leaves are preparing to drop by turning a pinkish crimson. This color, developing for now on leaves towards the ends of the topmost branches contrasts nicely with the still forest green leaves and the few fruits starting to yellow.Fall color of hardy orange

The problem with the fruits, gustatorily, is that they’re not very juicy, and they are very tart, somewhat bitter, and seedy. Still, they can be used to add a bit of home-grown citrus flavor to an -ade (Flying Dragonade?), fish, etc.

I Plant A Seed

New hardy orange plants are easy to raise from seed. The most important ingredient, as with other citrus, is not letting the seeds dry out once extracted from the fruit.

With most plants, you don’t get an exact replica of the mother plant in seedlings. Plant a McIntosh apple seed and the resulting tree will not bear McIntosh apples. (Just as you are not a genetic replica of your mother.) It depends on what pollinated the mother tree and how the chromosomes sorted out. Even though peaches are self-pollinating, the offspring of a Redhaven peach won’t bear Redhaven peaches.

Plant a seed of Flying Dragon hardy orange (or some other citrus varieties, in general), and you could get more Flying Dragons, exact replicas of the mother plant. That’s because citrus are among the few plants that exhibit apomixis, that is, seeds within the fruits that develop from only mother plant tissue.

Other plants that also bear apomictic seeds are some species of onion and dandelion. Some coneflowers, apples, and raspberries also bear apomictic seeds, but only if the flowers are pollinated — even though the pollen does not insinuate itself into the apomictic seed’s genetics.

Not all the seeds within a Flying Dragon fruit are apomictic. Hence, not all will grow to become Flying Dragons.

Hardy orange seedlings

The seedling on right is probably apomictic

Further complicating matters, some seeds can develop into more than one seedling! And some of those seedlings growing from that one seed might be apomictic while others will be run-of-the-mill.

None of these complications interferes with my propagating Flying Dragons from seed. The contorted stems and recurved thorns are so distinctive that it’s easy to tell the Flying Dragons from the others. Apomictic seedlings also are generally more vigorous than sexually-produced seedlings.

Not Everyone’s A Fan

Southerners are not nearly as enamored with hardy orange as I am . The hardiness, the thorns, and the seeds’ enthusiasm to sprout make the plants a threat down there, where the shrubs grow from 8 to 15 feet tall.

Hardy oranges were introduced into the south about 150 years ago, possibly to contain livestock. There, the plants have spread to woodlands, forest edges, and fencerows to shade out native plants. The lack of affection for the plant might be summed up in a quote from a Texas publication stating that hardy orange “does respond well to bulldozing.”

While bemoaning not being able to grow southern magnolia, gardenia, camellia, and crape myrtle this far north, I am thankful for being able to grow hardy orange without any danger.


In Which I Emulate George Washington

It’s about 10 years since I planted the cherry tree, a sweet, self-pollinating variety called Stella, on  dwarfing rootstock. During that time, the trunk swelled to about 7 inches in diameter and the branches shot skyward to 20 feet.

Stella is now gone, and it was all my doing. She took ten years to grow but only about an hour to cut down (with my new Stihl cordless electric chain saw, which I highly recommend). Afterlife of her trunk is as firewood, her branches as chipped mulch.

I warned Stella, who never bore one cherry, that this was her last chance. Finally, this spring she was loaded with blossoms, for the first time, followed by a good crop of developing cherries. A couple of weeks later, all the cherries were gone, except for two green ones I noticed on a cut branch. The weather could not have been at fault, nor birds at this early stage in the game. My guess is either an insect, probably plum curculio, or that the tree from the nursery was mislabeled, and it wasn’t Stella. Most varieties of sweet cherry need another variety nearby to set fruit.

She was pretty, but not pretty enough to grow as a strictly ornamental plant.

Oranges, Outdoors, In New York!

Waiting to replace Stella was a citrus(!) tree, a tree I could not have planted even a couple or years ago. 

One reason I couldn’t have planted this tree is because it wasn’t a citrus tree back then. It’s a plant called hardy orange, previously assigned the genus and species Poncirus trifoliata. It’s always been a close relative of citrus, even used as a rootstock on which to graft commercial citrus trees. Only recently has it been fully welcomed into the fold and re-assigned the botanical name Citrus trifoliate. So previously I would have been planting a Poncirus but now I planted a Citrus. Same plant, different name.Citrus, Flying Dragon

The other reason I couldn’t have — or shouldn’t have — planted hardy orange under any name previously is because it’s only just barely winter hardy here. Winters of a few years ago were consistently colder and would have killed the plant down to the ground.

With stems cut back from cold, the plant would never have borne flowers, which have the look and delicious fragrance of other citrus flowers, or fruits, which look just like golfball-sized oranges. The flavor of the fruit is nothing to rave about, citrus-y yes, but also very sour, bitter, and not very juicy. Used with restraint, though, the fruits can be used for home-grown citrus flavoring.Hardy orange fruit

The stems themselves, and their ominous thorns are hardy orange’s selling points here. The plant is evergreen, not because it holds onto its leaves through winter but because the stems are bright green year ‘round. My hardy orange is the variety Flying Dragon, whose twisting and turning stems are lined with ominously large, recurved — and also green — thorns.

Flying Dragon is a very interestingly attractive plant that can be used as flavoring, which is more that could have been said for my Stella.

Gumi Good

Except for Stella cherries, this year is shaping up to be an excellent year for fruits, even apples, plums, and other tree fruits, which are always chancy on my farmden, which is a naturally poor site for fruit growing.

Among many other fruits in the offing is a bumper crop of bright red, gold-flecked gumi fruits (Eleaegnus multiflora). The fruits followed sweet-smelling blossoms that perfumed the air earlier in the season and are an ornamental adjunct to the silvery leaves. Plus, the fruits have good flavor if picked thoroughly ripe.

The birds are having a field day with the gumis, so I only get to eat the fruits in their puckery stage when just that hint of good flavor can be detected in the background.

I’ve hung old CD’s among gumi’s branches, also among my mulberries’ branches, hoping the flashes of reflected light will scare birds away. It probably won’t because visual deterrents, when they are effective, are so mostly against flocking birds. The gumis are being enjoyed mostly by robins and catbirds.Gumi, with CD

Let the birds have their fun. Black currants, which birds ignore, are also now ripe. And blueberries — my favorite — are ripening, and safe from birds enclosed in the netted “blueberry temple.” 


A Scented Wave

    For the past couple of weeks, every time I walk upstairs to my home office, a sweet aroma hits me like a wave a few steps before I reach the top stair. This wave pulls me forward, a room and a half away, to the Meyer lemon plant sitting in my office’s sunny, south-facing window.Meyer lemon tree in pot
    The wave began when only a single Meyer lemon flower had opened. Now, the plant, only a foot and a half high, is decked out with more than 20 flowers.
    This “tree” started life as a cutting I took from a friend’s old tree that anyway needed some pruning. With their bottom leaves stripped off, the 6 inch long stems rooted reliably in a few weeks after their bottom portions were plunged into a moist mix of equal parts peat and perlite, and transpiration was reduced with a clear plastic overhead. Bright, but indirect, light allowed for photosynthesis without cooking the plants in their “mini-greenhouse.”
    My most important job now is to keep an eye out for scale insects, which show up as either brown bumps (armored scale) or cottony tufts (cottony cushion scale) on leaves and stems. Rubbing off these insects or dabbing them with a Q-tip soaked in alcohol deals with them unless the population gets out of hand. Repeated sprays with horticultural oil can be the next line of defense.Pollinating Meyer lemon
    Every couple of days I pick up the artist’s brush lying next to the potted plant, and dab it on the tips of some of the flowers. I’m not painting; I’m picking up the yellow pollen from each flower’s male anthers and dusting it onto each flower’s, and neighboring flower’s, female stigmas.
    A good proportion of those pollinated flowers should go on to provide the next treat from Meyer lemon, fruit, which this plant usually bears prolifically. Meyer lemon is actually a hybrid of lemon and sweet orange, with both parents reflected in the flavor. A final plus for this plant is, in contrast to many other citrus plants, is that its stems lack thorns.

Another Fig Option

    Greenhouse figs still bear fruit; with low light and cool temperatures, they’re not worth eating. I did recently harvest a few figs from a Kadota fig plant that had been planted outdoors.
    “Had been planted outdoors?” So where is it now? It’s still outdoors, but not planted. It’s in a pot. Like my few other potted figs, the potted Kadota plant will move down to the basement before temperatures drop below 20°F.Potted Kadota fig in ground
    Unlike my other potted figs, the Kadota plant did not require daily watering all summer. Or yearly root pruning and repotting to give the roots new room to grow and explore. The reason is because Kadota is in an 18” diameter plastic pot with some holes I drilled in its side. In spring, I sunk the pot up to its rim into a waiting hole in a bed on the sunny, south side of my house. The plant’s roots wandered outside the pot into the surrounding soil through the existing opening in the bottom of the pot, as well as through the side openings. Once outside the pot, roots were able to fend for themselves garnering water and nutrients for the small tree.Potted Kadota, out of ground
    Kadota, like many other fig varieties (but few other kinds of fruits), bears fruit on new shoots. Very convenient. Rather than having to squeeze spreading limbs down my narrow basement stairs, I can cut back all the stems rather drastically, which also has the benefit of stimulating vigorous, new shoots at the cut stub, new shoots that will bear fruit next year. Not too drastically, though, or too long a time might be required for the fruit to develop and ripen. And Kadota is already a late ripening variety.
    Of all my figs, Kadota is my favorite, both for its almost chewy skin and the rich, sweet flavor lying within. Even those recently harvested ones.

Comely, Fragrant, and Poisonous

    Another sensory treat slated for winter comes compliments of Angels’ Trumpets (Brugmansia spp.). The flowers of these poisonous(!), subtropical trees are giant, 6 inch long trumpets in pale colors and from which wafts a delicious aroma, especially at night. These subtropical plants can grow into trees but are easily kept much small, in pots, in cold climates.

Angels Trumpets, in past years

Angels Trumpets, in past years

    I neglected my plant all summer and on into fall; when I retrieved it to protect it from coldest nights, it was just about leafless and ready for the compost pile. Then I noticed some small leaves beginning to develop along its almost bare stems. And some stems had the beginnings of flowers on them.
    So I brought Angels’ Trumpet indoors, next to a sunny window (and next to the Meyer lemon). It looks sad now but should revive and, judging from my previous experiences with this plant, flower well most of winter. In summer, with long days, it takes a rest from flowering — which is why I ignored the plant.


More Citrus in the Making

You wouldn’t think that a couple of small, green sprouts could elicit so much excitement. Especially this time of year, with vigorous, green shoots sprouting up all over the place. But they did, in me. Not that anyone else would notice the two sprouts.
    The sprouts were from grafts I made a couple of months ago. Over the years I’ve done hundreds of successful grafts; these two were special.
    The first was citrus, special because the trees are subtropical and evergreen. The many apples, pears, and plums that I’ve grafted over the years are deciduous. I graft them when they are leafless and just about ready to start growing. Because the grafts are leafless, the wood, as long as the graft union is sealed, won’t dry out.
    Not so for citrus, more specifically for the stems I clipped off my potted Golden Nugget tangerine tree. What was needed, then was a rootstock on which to graft that stem. The result would be a Golden Nugget plant above the graft (which stays right where it is no matter how much the plant grows). Clipping all the leaves from the stem forestalled moisture loss.
    My home is also home to kumquat, another citrus that lives in a pot here, outdoors in summer and in a sunny window in winter. A couple of February’s ago, I glanced down at the kumquat seeds I had just spit out from fruits I harvested and ate. Not being able to squander their potential, I planted them in pots. A decade might have gone by before they were old enough to bear fruit but, after two years, the pencil-thick stems were large enough for grafting.

Citrus graft, a success

Citrus graft, a success

   With kumquat rootstocks poised for the operation and Golden Nugget scions (the stem to be grafted atop the rootstock) stripped of leaves and also ready, the procedure was the same as for apple trees and other deciduous plants: matching, sloping cuts on rootstock and scion held in place by a wrapping with a rubber strip; covering the wound to prevent moisture loss. My usual choice of covering is Tree-Kote, which gets painted on, or Parafilm, a stretchy film that adheres to itself.
    The citrus scion was fleshy enough to also lose moisture right through the bark. To prevent this, I wrapped the whole scion in the Parafilm. A blackened scion had followed previous attempts at grafting citrus without wrapping the stem.
    A week or so ago, it was time to unwrap the Parafilm from around the stem. If the grafted parts were going to knit together, they should have done so by then. Lo and behold, a small, green sprout soon pushed out from the top bud of the scion.

 Nutty Grafting

    Not all deciduous trees are as easy to graft as apple and pear. Nut trees in the Juglandaceae family, which includes black walnuts, English walnuts, butternuts, pecans, and hickories, are notoriously difficult. Part of the reason is because cutting a stem in spring, which is, of course, unavoidable when grafting, makes these trees bleed, messing up the works.
    With a slew of failures at grafting this family under my belt, I needed to try again. The candidate this year was a nut tree called buartnut, and hybrid tree with a hybrid name, the latter a non-euphonious combination of the words “heartnut” and “butternut.” Heartnut is a Japanese species of walnut, notable mostly for how easily it cracks to yield two heart-shaped nutmeats. Butternut is a richly flavored nut borne on a native tree that is becoming increasingly rare because of a blight disease.
    Buartnuts allegedly need cross-pollination to bear nuts. My tree, large and spreading though only about 15 years old, lacked a mate. The mate needn’t be a whole other tree; a branch from another tree, grafted on my tree, would suffice and avoid the need to plant a whole new tree or wait the years it would take to flower. Grafted branches bear much more quickly than new trees.
    Fortunately, I knew of another buartnut tree that could provide pollination. Last winter, I clipped off a few of its stems, packed them in a plastic bag, wrapped the bag in a wet towel, and then packed that whole mess into another plastic bag and then into the refrigerator. There, they remained hydrated and dormant until needed.

Heartnut graft, one sprout

Heartnut graft, one sprout

    The key, I’ve been told, to grafting Juglandaceae, is to wait in spring until a spate of 80 degree plus weather is predicted. Conditions seemed right on a day last May. Because of past failures, I attempted numerous grafts, three different kinds: the bark graft, the banana graft, and the whip graft. To promote bleeding off-site rather than at the grafts, I slit stems below the grafts. I covered one of the bark grafts with a plastic bag and then, for shade so the stems wouldn’t cook, a paper bag.
    Almost all the grafts failed. Except one. Just one stem of just one of the bark grafts (each of these bark grafts carries 4 or 5 stems) sprouted. How exciting!

Temple Disruption

    Exciting goings-on in the blueberry patch also. Birds are flitting about every morning, enjoying a few berries despite our repeated efforts to secure any openings in the walk-in “Blueberry Temple.” I threaded some string to more tightly join the top and side netting. As previously, I think this will solve the problem.
    Then again, this may be a Darwinian experiment. Birds never used to work their way into the Temple. Openings in the top netting are 1” across; I fear the net is breeding for smaller models of cedar waxwings and catbirds. Or perhaps smarter ones better at finagling their way to the blueberries


Paradise Under Glass, and I Take a Bit of it Home

Wandering in and out of the narrow alleys, I could barely squeeze past other, potential buyers. On my way back from a lecture and book selling, a wad of money was burning a hole in my pocket. I muttered to a young couple who glanced up to let me pass, “I feel like a drug addict.” A fleeting, sympathetic smile, and they, like others, were again intent on the offerings, hardly aware, like us other “addicts,” of other humanity.Inside Logee's Greenhouses.

I was lucky, able to leave Logee’s Greenhouses in Danielson, CT only $75 poorer. But richer in plants. Perched on the tray that I carried to my car were small plants of fragrant wax plant (Hoya odorata), Nordmann Seedless Nagami kumquat, and Golden Nugget mandarin (tangerine), all three promising to offer, for years to come, sweet fragrance, beauty, and good eating in the case of the mandarin and kumquat. By not allowing myself to dawdle, I was able to keep my trembling hand from grabbing at a Black Mission fig plant, a Dwarf Cavendish banana plant (“only 3 feet high!”), or a Hoya lauterbachii, with fragrant blooms the size of teacups. 

Most of Logee’s plants are small and not cheap, understandable considering the wide array of plants they stock. Aside from my kumquat and mandarin, I could have chosen from among a dozen other citrus varieties, including some interesting oddities like Buddah’s Hand Citron, whose fruit does, in fact, look like the draped fingers on a hand. Instead of the fragrant wax plant, I could have driven home with any one of 15 other species or varieties of wax plant. Not that Logee’s is limited only to fragrant or fruiting plants. They stock almost a 100 different kinds of begonias, among other houseplants.

Part of the jasmine collection at Logee's

Part of the jasmine collection at Logee’s

Entering the greenhouses is an experience very unlike that of entering most commercial greenhouses, the latter with their soaring roofs of crystal-clear glass, their buoyant atmosphere, and scoured concrete floors. Logee’s is Paradise for plant lovers, with a mix of concrete and dirt paths so narrow that leaves and tendrils grab at you from either side. Fortunately, plants are more organized at Logee’s than in Paradise: collections of such plants as citrus, passionflower, orchids, and angel’s trumpets are each grouped together. Perhaps the star of the show is the Ponderosa lemon tree, shipped by train then horse and buggy to the greenhouse in 1900 and still bearing crops of grapefruit sized lemons (also called American Wonder lemon and thought to be a hybrid of lemon and citron, originating as a seedling the 1880s). Over the years, it’s given rise to numerous offspring, one of which you can purchase, growing in a 2.5” pot, for $11.95.

Citrus: New Plants from Old

New plants of Ponderosa lemon and other citrus varieties can be propagated one of three ways.

Lemons and limes tend to root easily from cuttings, which are leafy branches with their bases plunged into a moist rooting medium such as a 1:1 mix of perlite and peat moss. Because citrus are evergreen, air around the cuttings has to be kept humid enough so the still-rootless stems don’t dry out. A clear plastic or glass tent does the trick. The leaves need to photosynthesize so they have energy to make roots, so some light is needed. Not too much, though, or the cuttings cook in their tent.

Special rooting hormones, which are synthetic analogues of natural plant hormones, help cuttings to root. Synthetic hormones are used because they decompose more slowly than natural hormones (and in different concentrations, are used as herbicides, such as 2,4-D). Another possibility is to soak the cuttings in water in which have steeped stems of willow, a plant that roots very easily so presumably has some root-stimulating goodies to share. I avoid the hassle of natural or synthetic hormones in rooting cuttings and, instead, pay careful attention to which stems I select for rooting, the rooting medium, and light.

Some citrus varieties can be propagated by seed. Usually a seed-propagated fruit gives rise to a baby different from the mother plant, reflecting the jumbling around of chromosomes as pollen and egg cells united. However, a few plants, and many citrus, exhibit apomyxis, where the seeds, although they look like normal seeds, are formed from cells of only the mother plant.

My new plant acquisitions: hoya and 2 citrus.

My new plant acquisitions: hoya and 2 citrus.

All the seedlings, then, are clones of each other and their mother. Well, not all, because in a given fruit, some seeds may be apomyctic and others may be the product of pollination. The apomyctic seedlings show their presence by their greater vigor and more upright stature.

Downsides to propagation by seedlings, apomyctic or otherwise, are that plants must go through a juvenile phases of some years before they are old enough to flower and fruit. Also, most citrus tend to be very thorny in their youth.

Kumquats Roots for Tangerine Tops

One way I justified my purchases at Logee’s was with my plan to use my new citrus plants to make more plants — by grafting, the third way of propagating citrus. All that’s needed is any citrus rootstock; they all are graft compatible. Not being able to throw away seeds, I have a few kumquat rootstocks started from seeds I spit out from my Meiwa kumquat fruits as I ate them a couple of years ago.

I’ll graft in spring, taking stems from the Golden Nugget mandarin to make a whip graft, a particularly easy kind of graft that gives quick results. Basically, a smooth, sloping cut on the kumquat rootstock will be matched against a similarly smooth, sloping cut on the “scion,” which is the stem I cut from the mandarin stem, with both bound together with a wrap of tape or cut rubber band. After removing leaves from the scion, grafting compound (Tree-Kote) or Parafilm seals the graft and scion against dessication before the scion and rootstock knit together, and the scion piece begins to grow.

The final step will be deciding what to do with my growing citrus orchard in pots. Plants for my annual sale, perhaps? The largest citrus orchard (potted) in the Hudson Valley?

Nuts for Fruits

What a fool I am; I can’t even follow my own advice! A couple of days ago I planted an apricot tree that I had ordered a few weeks previously. All of which compounds my foolishness because I had plenty of time to ponder the purchase, even cancel it if I came to my senses before it’s arrival mail-order.
Planting an apricot tree may not seem foolish to you. But it is, as I’ve advised many people. The reason is that here in the northeast, perhaps even east of the Rocky Mountains, an apricot is unlikely to bear fruit. The plant hails from regions where winters are steadily cold and spring temperatures creep steadily upward. Over most of continental U.S., winter temperatures fluctuate wildly up and down, predisposing the plants to

My apricot hope for the future.

disease such as ominous-sounding, and truly debilitating, valsa canker. Trees typically die either quickly or slowly.

If only that were all . . . Apricot blossoms open at the first hint of spring warmth. The pinkish buds unfolding against the brownish red stems are a beautiful and welcome sight on the heels of winter, but those early blooms could — usually are — knocked out by subsequent frosty weather. Damaging, late frosts are least likely to occur near large bodies of water, such as the ocean and Great Lakes. Late frosts are most likely to occur in low-lying regions into which cold air sinks on still, spring nights; that would be here on my farmden in the valley of the Wallkill River.
If only that were all . . . Even if the trees stay alive through winters and their blossoms escape spring frosts, the fruits themselves are the target of a number of insects and diseases. Plum curculio, oriental fruit moth, brown rot, black knot . . . the list goes on of afflictions that can reduce the crop to zero. Oh, and did I mention squirrels. My father had a tree that every Father’s Day was stripped of every one of its small, green developing fruits by squirrels.
Did you ever taste a perfectly ripened apricot, one that’s soft and ready to travel no more than arm’s length from the branch to your mouth? I have (when I worked at the USDA Fruit Laboratory and at a friend’s orchard; he has a good site). Perfectly ripe, the fruit tastes nothing like a lemon, as market apricots usually do, but has just a hint of tartness to offset its rich, sweet flavor. For that, I planted the tree.
My friend Lev with his apricot trees
I wrote that “apricot is unlikely to bear fruit.” “Unlikely” does not mean “never.” A crop of apricots even one year out of — say — every five years will justify, for me, the space and trouble the tree will entail.
I was smart in a couple of ways with my apricot tree. I bought it from a nursery that specializes in fruit trees ( and I planted in full sun in well-drained, moderately fertile soil. And the variety is Jerseycot, one of the varieties most resistant to some of the pests and the vagaries of our winter and spring weather.
More foolishness: I just received a confirmation for a nursery order, soon to arrive, that includes a camellia bush. Let me explain. I love living in the northeast but do bemoan the inability to grow certain plants not hardy here, among them southern magnolia, citrus, and camellia. I’ve been tempted to plant the hardiest southern magnolia, Edith Bogue, but

My “citrus” plantation.

restrain myself realizing that the plant might survive but would never become a majestic specimen the tree is meant to be. Citrus? I resign myself to growing some citrus in pots, indoors in winter and outdoors in summer.

The last few years have seen the development of hardier camellias. Long Island Pink is one of the hardiest, with compact stature, glossy evergreen leaves, and single pink flowers in autumn. Still, it’s not really hardy here. I’ll plant it in the partial shade near the northeast corner of my home, protect it through winter its first few years as it develops cold-hardiness, and perhaps my foolishness will pay off.

Citrus, Flying Dragon

Citrus in New York?

Winters have been warmer here for the past few years and, so far at least, this winter is playing out to be the warmest ever. But even the “global warming” cloud has its silver lining. Snow is great fun and cold is invigorating but one of my regrets in living in a cold winter region has been not being able to harvest fresh citrus fruits from outdoor trees. If things keep progressing in their present direction, as predicted, that situation may change.
The coldest temperature so far this winter has been down around 9° F, and three of my citrus plants still look fine. In the ground, outdoors! Technically, they are a citrus relative, Poncirus trifoliata, also known as trifoliate orange. The leaves resemble citrus leaves, the white flowers resemble and have the fragrance of citrus flowers, and the fruits, orange and an inch-and-a-half across, resemble citrus fruits inside and out. Too bad poncirus is barely edible, although it can be squeezed for juice that is diluted and sweetened to make an -ade.
Flying Dragon poncirus
Even if poncirus was not edible, it would be worth growing for its beauty, especially the Flying Dragon variety with its contorted, green (and thorny) stems and leaves.
My three poncirus plants started out as seeds plucked from a fruit on a plant growing against a brick wall in northern New Jersey. The seeds sprout and grow easily. After growing one year in pots, into the ground they went. The first couple of years, winter lows of -10° and -19° killed them back to the snow line. They’re allegedly cold-hardy below zero degrees F., but that hardiness comes with age. Also, the pattern of cold development and its duration affects cold-hardiness. This year, so far, the plants look fine from top to bottom.
Poncirus is close enough to citrus botanically that its been hybridized with citrus to make more edible, albeit less cold-hardy, hybrids. Like the citrange, from the mating with sweet orange, hardy to 5 to 10°F. A few varieties of citrange have been developed, all billed as “approaching edibility” but, like poncirus, making a good -ade.
Not to give up on true citrus — yet. Probably the hardiest is yuzu, a hybrid of a sour mandarin and the barely edible Ichang papeda (C. ichangensis). Ichang papeda is the hardiest evergreen citrus. (Poncirus sheds its leaves in winter.) So yuzu is a true citrus and it is quite cold-hardy, down to about 10°F. And it is eaten. The great plant explorer, Frank N. Meyer described it, in 1914, “rind full of oil glands, smelling like a fine lemon; segments separating easily; fairly juicy and of an agreeable sharp sour taste.”

Mandarins (tangerines, C. reticulata) are also among the hardiest of citrus, and they taste very good straight up. The deep orange fruits of the variety Changsha are sweet and juicy, and I actually have a potted plant from which I’ve been trying to coax fruit for more than 5 years — or so I thought.
Today I checked the original bag in which I received cuttings of the alleged Changsha. Turns out the name scrawled on the bag is Changshou, not Changsha. Bummer, I was looking forward to Changsha. Changshou is another hardy citrus-type fruit, actually a kumquat, from the closely related genus Fortunella. Kumquats are cold-hardy to between 10 and 20°F., and are a fruit I’ve grown — indoors in winter, outdoors in summer — for many years. 

Meiwa kumquat
Kumquats, like poncirus, hybridize readily with citrus species. Hmmm, why not combine the hardy kumquat with the hardy mandarin? It’s been done, the result of the mating being the Nippon orangequat, hardy to 10°F. and with a mild flavor, if left to hang on the plant long enough, and, like a kumquat, having an edible skin.
Except for poncirus, I’m not really hoping to harvest any citrus-type fruits from outdoor plants anytime soon, perhaps ever. Surviving the depths of winter cold is one thing. The plant also has to be able to ripen its fruit within the growing season. My Meiwa kumquats, for instance, ripen in February, and I expect even a few nights in the 20s would turn the fruit to mush.
For now, then, I continue growing the more edible citrus-type fruits in pots that winter indoors. Still, poncirus, that citrus look-alike will look cool out in the landscape.