A Gardening Journal

Today in the Garden of a Lifetime: Hardy Oranges in Fruit

Hardy orange is almost too interesting a tree, mounting a different striking and often unique display each season: spring flowers, summer foliage, fall fruit and foliage—and then, in winter, the green bark of bare young twigs and the horrifyingly fierce thorns. No other plant hardy to Zone 6 has a stronger claim as the most interesting month after month, decade after decade.

 

As if this repertoire weren't broad enough, hardy orange can be pruned into a hedge or topiary, adding sharp geometry to the show. If you have room or commitment for just one of these astonishing trees, topiary is the way to go despite the dangerous excitement of the annual pruning of a plant whose thorns are sharp, long, and rigid enough to pierce a careless hand or foot. Many other woody plants provide exciting flowers, fruit, and fall foliage; some also bear thorns that are colorful and even dangerous. Far fewer can also be formed into topiary.

 

That said, a free-range Poncirus trifoliata is still a particular thrill, because the tree will flower heavily in spring and fruit just as heavily in fall. And such fruit they are: without question, citrus—and yet produced by a tree that can happily grow in a garden a thousand miles from Orlando. There's no other citrus hardy as far north as Boston. If you want the "What's that amazing tree doing thriving here?" frisson of citrus north of South Carolina, hardy orange is it. 

 

Branches formed the previous season provide most of the floral and fruiting show. This stands to reason, in that woody plants that flower in spring typically need to begin bud formation the previous summer and fall so as to be able to leap into action when warm weather returns.

 

Poncirus trifoliata fruits stems green foliage overall 102816 640

 

See the branch laden with fruit that's still small and green? It's likely that it is the exceptional case of flowers forming de novo on a first-year stem. I didn't check on this particular hardy orange through the summer—I have (gulp) four of them—but such "new growth" flowers would have also had to have emerged in summer: The new growth itself needed to emerge first, leaving a too-short ripening season of just late summer to frost.

 

Poncirus trifoliata green fruits cropped 102816 640

 

Below, a shot of my topiaried hardy orange. It also bears flowers and fruit but, because the annual pruning encourages such a heavy outer layer of new growth, the fruitful older growth is largely hidden. (The flowers emerge in Spring before that new growth has started, so are nicely displayed.) But a casual viewer wouldn't even notice the fruit. Despite their being bright orange and the size of ping pong balls, by the time they show color in October, they've become nestled deep within the topiary's dense shaggy canopy of new growth.

 

Poncirus trifoliata 102916 640

 

Even a bit closer, the fruit is barely visible.

 

Poncirus trifoliata middle head showing both ripe at top unripe fruit 102916 640

 

Note the small green fruits on some of the ball's upper twigs. These are "new growth" fruits like those displayed by the branch of the free-range tree. Here it's even clearer that they are, in fact, born on twigs formed this season: The topiary was shorn of last season's growth in the fall. Plus, these fruits are formed at the very tips of the growth; fruits formed on older stems are never at those stems' tips, because additional vegetative growth emerges from those tips each spring.

 

Poncirus trifoliata middle head showing top unripe fruit 102916 640

 

Only in close-up are the colorful mature fruits more noticeable. Still, it's a weak display compared to the bouyant, bountiful, open show of fruits on the free-range tree.

 

Poncirus trifoliata middle head closer 102916 640

 

The normal season for pruning hardy orange topiary is during the cool months of fall and winter. If I get to it in time, I can remove almost all of the leafy but largely fruitless new growth, to expose the shapely rounded topiary contours of the older growth while its fruits are still in place.

 

A free-range hardy orange, however, provides a generous show of fruit and flowers each season all on its own, but lacks the striking shape that pruning provides. A topiaried hardy orange is far more of an achievement—you've braved the dangerous thorns to create it, after all—and provides magnificent as well as storm-proof geometry no matter how rough the winter. But it bears fruit sparsely, and displays it only after a well-timed mid-fall pruning.

 

If you have the room, grow Poncirus both free-range and as topiary. Then this species can more easily flaunt its fullest range of seasonal displays.

 

Here's how to grow hardy orange. The pruning strategy I recommend in this subsequent post lets you have your cake and eat it too: One year, the tree displays a healthy crop of flowers and fruit, while the next it regains its topiary shape.

 
 
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