A Gardening Journal

The Best Season Ever: Jacaranda in Bud

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In the tropics, a jacaranda in flower is the norm: The tree is wildly popular wherever it's hardy, and you're as likely to see streets lined with it in Nepal, South Africa, and Brazil as in southern Florida or California. Anytime from Spring to mid-Summer, large racemes of lilac buds emerge from branch tips. They mature to flowers that are remarkably similar in size, coloring, and array to those of Paulownia tomentosa. (Indeed, from this Northerner's perspective, jacaranda is the empress tree of the south.) The difference is that jacaranda can be in flower for nearly two months; paulownia might be in flower for two weeks.

 

In the late-in-the-day light, below, the buds appear to be blue.

 

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Jacaranda isn't hardy in climates that are colder than subtropical, where frost would be a typical Winter occurance, not a once-every-few-year stunner. So, while mature trees will survive a rare frost, there will never be a street north of Orlando, Florida, that will be lined with jacaranda long-term. Fortunately, jacaranda thrives and—as here!—flowers when grown in containers.

 

Here's how to grow this spectacular tropical tree:

 

Latin Name

Jacaranda mimosifolia

Common Name

Jacaranda. "Jack-a-RAN-da" is the pronunciation; the name is thought to be derived from Guarani, an indigenous language of Paraguay. If the origin were Spanish, the pronunciation might, instead, be "hock-a-RON-da."

Family

Bignoniaceae, the Trumpet Vine family.

What kind of plant is it?

Deciduous subtropical tree. 

Hardiness

Normally Zones 10 - 11, with survival down to 9b when mature and under ideal circumstances. Jacaranda is subtropical in terms of its frost tolerance: Older trees can survive a rare dip into the low 20s Fahrenheit. The trees are not subtropical in terms of heat tolerance or requirement for a Winter chill: They thrive world-over in the tropics, and enjoy heat as well as humidity. See "How to handle it," below.

Habit

Upright but, often, multi-trunked, with gracefully spreading branches.

Rate of Growth

Fast.

Size in ten years

Twenty-five to fifty feet tall. Trees often attempt to form multiple trunks (and should be discouraged from doing so; see "How to handle it," below); such individuals can spread as wide as high. The width of a single-trunked tree is usually narrower than its height.

Texture

Thanks to the foliage's extremely small leaflets, a jacaranda in leaf is a superlative feathery presence in the warm months. Flowering often precedes emergence of new foliage, and can be so profuse as to create a canopy that's notably denser than that formed by the foliage to follow. Thanks to the arching branches, the trees are a pleasing presence even in their cool-season deciduous phase.

Grown for

its flowers: With the possible exception of Delonix regia, no tropical tree is as brilliantly colorful in flower, delicate in foliage, and graceful in habit. But it's the flowers that are the calling card. Trumpet-shaped, similar to those of trumpet flowers or foxgloves or chestnuts, they are borne in the tens of thousands, in large racemes that cover the tree. If the preceding Winter has been drier, flowers tend to appear in advance of the foliage, which simplifies and, therefore, intensifies their show. Otherwise, foliage and flowers can emerge simultaneously or, as in the case with my container specimen, flowers can follow the foliage by some weeks. The flower color can vary (as can the apparent color as captured through photography). Usually, the color is pale lilac-blue, but the full range from white to violet has been reported. Maddeningly, almost no cultivars are available—see "Variants," below. These fast-growing trees are often propagated from seed, which means the color of flowers tree-to-tree in mass plantings might not be consistent.  

 

its length of flowering: Jacaranda is reported as being in flower for nearly two months.

 

its reliability: As long as it receives full sun, jacaranda is so tolerant of soils of differing degrees of fertility and pH, drainage, compactness or loose-ness, depth, and overall availability to the roots of a full-size tree—let alone to being used as a target of peeing dogs, and a hitching post for animals, carts, scooters, and bicycles—that it can be (and is) planted as a street tree by the thousands at a clip. Jacaranda enjoys the monoculture mania in the subtropics and tropics that the American elm once enjoyed as a street tree in temperate North America. When the jacarandas are in flower, entire blocks, neighborhoods and, even, cities as a whole sport a lilac-blue haze. There are an estimated 70,000 jacaranda trees just in Pretoria, South Africa, which bills itself as the Jacaranda City. And it has competition: More than a few cities in Australia feature the trees prominently, and mount annual jacaranda festivals to celebrate them. Streets flanked by rows of jacaranda can be found in Zimbabwe, India, Nepal, Brazil, and, no doubt, many other locales where the tree is hardy. In the United States, the trees are popular in southern California (San Diego in particular), southern Arizona, and southern Florida. If the species were fussy in establishment or maintenance, brief in lifespan, or unduly susceptible to damage from rough weather or serious pests and diseases, such global prominence would be impossible. 

 

its graceful foliage: Bipinnately compound leaves have notably tiny leaflets, very similar to those of jacaranda's only other competition for postcard-worthy shots of the bodaciously colorful trees of the tropics, Delonix regia.

 

its graceful habit: When the tree receives some formative pruning in youth (see "How to handle it," below), the arching layered canopy is high enough that pedestrian and vehicular traffic is unimpeded. Thank goodness: Jacaranda mimosifolia is planted world-wide as a street tree.

Flowering season

Spring into Summer: In the northern hemisphere, late May into June and even July. In the southern, October into November.

Color combinations

The lilac-blue flowers and their darker-blue buds can coordinate with just about any shade: white, yellow, pink, orange, red, other shades of blue, violet, burgundy, ebony, and black. Although each flower is a pale thing, they appear in countless thousands on a mature tree—in the millions for the block-after-block displays jacaranda trees inspire—and, so, by dint of overwhelming scale, these pastel flowers can hold their own near colors of ultimate saturation and intensity. See "Plant partners," below.

Plant Partners

For a tree with such grace and popularity, let alone a world-famous floral display, Jacaranda mimosifolia presents an unusual array of challenges for use in mixed plantings. Because jacaranda in bloom creates such a powerful show all on its own, it's understandable that the tree is often planted as a soloist—or as an army of soloists, so to speak, when used as a street tree. When jacarandas lining both side of the street are in flower, what other plants could compete? And with such a long flowering season, a follow-up period of coloristic neutrality might be a relief. Further, non-gardeners may well conclude that, if they plant just a jacaranda in their front yard, they've already done more than enough to boost horticultural excitement in the neighborhood. Plus, the tree clearly tolerates the relative hardships of street-tree siting—cramped root runs, compacted soil, peeing dogs, pollution from vehicles—and it's the great exception if a street tree receives any companion plantings at all. All in all, it's no wonder that jacaranda trees are so often seen without thoughtful horticulture nearby. 

 

The tree's steady release of litter—leaves, flowers, stems, seeds—also creates practical challenges to significant underplantings. It's possible (but not easy) to sweep the profuse, diverse, and, often, sticky detritus from paving, or rake it off of grass. But even the most patient and obsessive gardener would likely become overwhelmed by the task of regularly wiping detritus from each leaf of broad-leaved plants, especially if their foliage were arrayed horizontally. Even doing the wash-down with a hose would grow tedious, month after month. Plus, what a waste of water.

 

Instead, consider plants within this wide-spreading tree's "litter shadow" that are limited in extent (so you can, as necessary, reach in to clean them) as well as graced with upright grassy or sword-shaped foliage (so that most detritus will simply fall between the vertical blades). What you're looking for, then, is a semi-shade-loving specimen with enough drama to be planted under the jacaranda's canopy as a singleton—an exclamation point amidst the carpet of the tree's attractive fallen flowers. Philodendron selloum has the oomph and scale, but its wide leaves would catch detritus like crazy. Cultivars of Phormium tenax might be ideal. In texture, habit, scale, and coloring, a colony of phormium could provide terrific contrast.

 

Choose forms with upright foliage; the leaves of some cultivars arch strongly and, therefore, would be more likely to retain jacaranda detritus. 

 

Dianella tasmanica 'Variegata' would provide similar interest at a fraction of the scale: mature plantings are usually less than two feet high.

 

Doryanthes palmeri is another option for large-scale settings: The foliage of this titanic phormium-like lily can form a clump ten feet high and broad. If possible, site the clump at the south or west margin of the jacaranda's canopy, so it can receive some direct sun.

 

Neomarica caerulea is reported to be a foolproof underplanting for jacaranda: The blue of tropical iris's Spring flowers coordinates well with the tree's blue buds and lilac flowers. Plus, the species blooms in waves, one of which is certain to occur during the jacaranda's very long flowering season.

Where to use it in your garden

Although jacaranda is planted as a street tree worldwide, it's such a messy tree that there's a real trade-off between beauty and practicality. See "Downsides" for the surprisingly long and diverse list of the tree's ever-falling debris. Further, the canopy of a mature jacaranda is wide, but the tree doesn't lend itself to pruning whose goal is size reduction. (Again, see "Downsides," below.) So the tree isn't suitable for small properties, where its litter would drift down onto every surface. In particular, jacaranda should never be sited anywhere near water features, whose mechanics can become clogged by the refuse. And, although the delicate pinnate foliage creates only light shade, the near-continual rain of tree fragments makes companion horticulture a challenge. (See "Plant partners," above.) There's enough light for lawn, which is, handily, the only horticultural groundcover that can also allow as well as tolerate the frequent raking or sweeping needed to keep the tree's mess in check.

 

It's  striking, then, that a tree that is universally loved—and planted—can be so difficult to site wisely. Ideally, plant jacaranda far out in large lawns where the tree is removed from vehicular or pedestrian traffic but is still fully visible as well as accessible. The tree's spreading canopy and reasonable size make it effective when planted as a specimen, even in large spaces. For example, it would be impossible to resist the pilgrimage to a single jacaranda at the far end of very deep lawn. But the thrill of the spectacular flowers is only heightened when jacaranda is planted in multiples. An informal grove spreading over a rolling acre (or ten!) would be astounding, as would be a plantation-style grid of jacaranda extending far out into level terrain. Just because there are already countless streets lined with jacarandas on both sides doesn't at all diminish the species' impact when used as an allée. If the road were infrequently used, and not lined with parked cars covered in the flowers' sticky nectar, the integrity of the carpet of fallen flowers forms with those still emerging in the canopies above would be maximized. See "Quirks," below, for possibiities to enhance the display of a jacaranda's fallen flowers.

 

If possible, emphasize the irregular habit of the tree's architecture by siting with a high wall at the back. Jacaranda's best location, then, would be on a very large property that, oddly, also had a very broad institutional or even industrial building as a backdrop. If the facade in question is deficient in windows or detailing, so much the better. Surely, somewhere in the world there's a resort or municipal complex in Zone 10 or 11 with a brick building two or three stories tall—a former mill, say—and three hundred feet long, that also abuts a couple of acres of field. A platoon of jacarandas would be all that's needed to transform this austere and even boring setting into a stunning magazine spread.

Culture

Full sun. The trees enjoy heat and humidity. Although sandy, fertile, well-draining soil is ideal, judging from the millions of jacarandas that succeed as street trees world-wide, the tree must be able to succeed in almost any soil that isn't poorly drained.  

How to handle it: The Basics.

If growing at the cooler end of jacaranda's hardiness range, plant in Spring, ideally when the tree is still leafless but the emergence of flowers or foliage is imminent. If planting where the temperatures are warm year-round, planting can occur at any time. Water to ensure establishment, especially if planting occurs during a drought or a normal dry season.

 

The tree often needs formative pruning when young to counter its tendency to form multiple trunks. Besides resulting in a lower canopy that might not permit passage of vehicles and pedestrians, multiple trunks make a tree more susceptible to damage in high winds: The less vertical of the trunks tend to be less securely anchored. 

 

Prune basal shoots off promptly, as well as any resprouts that, annoyingly, your pruning may well have encouraged. Such shoots have the descriptive name of watersprouts. And, indeed, they seem to grow quickly, with a defiant verticality that disrupts the tree's irregular and arching style of branching. The smaller and shorter these shoots are at the time of pruning, the less disruptive their removal will be. Young jacaranda trees, then, repay your watchful and proactive stewardship by maturing with a more space-efficient single trunk and a canopy that's free of watersprouts.

 

It's often not advisable to attempt to retrain jacarandas that have been allowed to grow free-range, by pruning major limbs or removing multiple trunks. Too often, you'll only cause production of a profusion of water-sprouts that, seemingly, restore the tree's original dimensions within the season. In contrast to the proactive formative pruning when the tree is young, pruning mature trees is usually done only when truly necessary and, even then, only after the need is clear: A limb has died, say, or a subsidiary trunk has split apart from the main one. Alas, after the pruning is completed, there's a follow-up period of proactive "watersprout watch."       

How to handle it: Another option—or two!

In my experience, jacaranda is an easy container specimen when young. The tree grows with exciting speed and, even if it never flowered, the delicate foliage is a thrill in itself. Plus, its deciduous phase makes it simpler to overwinter. Before any danger of frost in late Summer or early Fall, bring the tree into frost-free shelter. Inevitably, the decrease in strength of the sunlight the tree receives, both as a result of ever-shortening days and from having been brought into shelter, will cause foliage to be shed. Reduce watering accordingly; water sparingly while the tree is leafless. As long as the conditions are well above freezing (judging from my success at bringing a young tree in flower, a minimum of fifty degrees Fahrenheit is warm enough), a dormant jacaranda can be moved out of the always-in-short-supply sunny locations in your greenhouse or sunroom. You could even try storing the leafless and dormant tree in a warm but dark spot—even in the closet.

 

As Winter turns into Spring, be alert for swelling at the tips of branches, which could be either flower buds or new foliage. Increase watering as needed, and also bring the tree into as full sun as you can while still keeping it in warm shelter. Move outside only after balmy Summer temperatures are consistent.

 

As has been my experience, if you ramp up your watering too solicitously in response to swelling of leaf or buds, you'll encourage the dormant tree to rush into flower while it's still in the greenhouse. In any season, the flowers are thrilling, especially at a time when there may still be little in flower other than daffodils in your garden. But you may want your jacaranda to flower after the weather is warm enough for you to have returned the containered tree to your garden. This will probably be in mid to late May, which, conveniently, is when the tree would normally be coming into bloom anyway in climates where it's hardy.

 

How, then, to prolong a greenhoused tree's dormany even, as it were, against its will? Here's what I'll be trying. Since jacaranda is leafless when dormant, anyway, place the containered specimen where it doesn't receive much direct sun. This will lessen the warming the tree experiences during the day. No greenhouse mechanicals can maintain an even temperature roof to floor, front to back. While still ensuring that it remains frost-free, place the tree where its ambient temperature is cooler. (I might rest both of mine on their sides and, then, gently roll them under a greenhouse bench.) Finally, keep in mind that jacaranda is fairly drought-tolerant. Water only if the branch tips seem to be shriveling and, then, only a little. Watering out of misplaced kindness ("Wow, what a lovely warm day in the greenhouse in February! Maybe I'll give the jacaranda a drink.") will only encourage the tree into premature activity.

 

So far, so good. But because the tree's normal habit is to grow quickly—and its peak display is those gorgeous flowers—a containered jacaranda is likely to become difficult to handle as it grows larger and older. The usual tactic to keep a plant in bounds—pruning—is the very intervention that isn't advisable when this species is growing free-range. But only the grandest conservatory would have room for a jacaranda that reaches its mature dimensions. Each of my pair of containered jacarandas is about seven feet tall, including the height of their containers. In another year, they will be near the limits of convenience for transport to a greenhouse, let alone standing upright when inside it. Some kind of size control will be essential. Will production of watersprouts be as much of a problem when pruning a container-grown jacaranda? Or, counterintuitively, could the tree that shouldn't be pruned when mature be kept to convenient dimensions by growing it as a coppice? Perhaps the resultant watersprouts would flower in their second or third year, and could then be cut back to a stump. Maybe the tree's multi-trunk tendency and, admittedly, vigorous response to pruning could both allow it to be be morphed into a multi-stemmed flowering shrub, with some watersprouts maturing to flowering each season.

 

Or, best of all, perhaps height could be restrained through pinching soft tip growth right after any flowering was completed. The result would be a jacaranda standard: compact but still bearing flowers. Because the tree is omnipresent along streets and in gardens wherever it's hardy, its potential for space-efficient handling when growing permanently in containers is still to be explored.

Quirks and special cases

The flowers maintain their bright coloring so well after falling to the ground that the intensity and charm of the terrestial show of flowers can be nearly as enjoyable as that still continuing up in the tree's canopy. Further, trees continue to flower for such a long time—up to two months—that the arboreal and terrestrial displays can be effective simultaneously. Yes, this striking ground-level display is also a huge mess. Worse, bees are reported to be so engaged by the flowers that they visit them even after they've fallen; inevitably, this increases the chances of inadvertent and painful encounters with humans. This is just an introduction to the many, many, downsides to this mesmerizingly beautiful tree. See the fuller list in "Downsides," below.

 

Thinking more fancifully—as well as in the spirit of turning lemons into lemonade—it might be possible to handle the tree's day-after-day, week-after-week shower of released blossoms as less of a maintenance chore and more of a curatorial triumph. Any individual fallen flower is eventually going to lose its color, to transition from unexpected ground-level color that's worthy of savoring, to additional ground-level refuse that now needs to be removed. Depending on your climate and your particular tree's vigor and performance, there could be real variance in the tree's production of flowers and, therefore, the replenishment of the carpet of fallen flowers and the length of time a fallen flower retains its color. If all the flowers—newly fallen as well as already decayed—were cleaned up periodically, a fresh crop of fallen flowers would begin to accumulate. There could be a sweet spot of sweep-up frequency that results in the best combination of accumulation of attractive recently-fallen flowers and the minimizing of the proportion of them that are old enough to have turned brown. Sweeping once a week? Every three days? Twice a month?

 

Plus, the sweeping might also gently shift fallen blossoms closer together in between the wipe-the-slate-clean full clean-ups. I'm usually not a fan of backpack leaf blowers, but they might be the tool of choice here. A quick blow once around the perimeter of the carpet of fallen flowers could keep it more concentrated but with (probably) minimal damage to the fallen blossoms. The full clean-up could be done more quietly and with less pollution—with a rake—because the goal is now just to gather everything up, not preserve its integrity as it lingers attractively on the ground.

Downsides

Jacaranda is nearly as famous for its messiness as its beauty. Flowers, leaflets, the stems of the leaves, the seeds, and twigs are all shed; nearly year-round, there's something underneath a jacaranda that needs to be cleaned up. Although the tree is irresistible for lining roadways, this placement guarantees that parked cars are always littered. The detritus is reported as being difficult to clean off of concrete, too. Plus, the nectar from the flowers is sticky and is hard to wash off. Fallen leaflets decay, releasing a less-than-pleasant scent. Worse would be to grow the tree near swimming pools or water features. The tree litters heartily the entire swimming season: Flowers are present (and, therefore, falling) for nearly two months, and are followed by the leaflets, then the stems that bear the flowers as well as the stems that bear the leaflets, plus the seeds. The larger debris will be captured by pool skimmers (which need to be cleaned frequently lest they be overwhelmed), but the leaflets are so tiny that they can escape the skimmers and clog pool machinery itself. As if this weren't enough, the popularity of the tree means that its pollen can be so widely and heavily dispersed as to be a hazard for allergy sufferers. 

 

The tree is also a puzzle when it comes to pruning. On the one hand, formative pruning when young is strongly advised, so that the tree develops just one trunk. Multi-trunked trees are more likely to incur major losses during storms, because the lesser of these trunks tend not to be anchored as securely. But pruning also stimulates emergence of water-sprouts—very fast-growing vertical stems—that disrupt the tree's charac-teristic broad and somewhat pendulous habit. These should be removed as soon as they are noticed. Pruning, therefore, is not advised when the goal is to limit overall size: The watersprouts often recoup any temporary reduction in size in only months, while also ruining the tree's graceful architecture in the process. Trees that are older than fifteen years are reported not to need such pruning—which is another way of saying that, for a decade and more, young jacaranda trees are likely to need attention.

 

See "Where to use it" and "How to handle it," above, for advice on siting and growng jacaranda so as to minimize its drawbacks.

Variants

Because the flowers of Jacaranda mimosifolia can vary from white to deep purple, and this species is grown by (probably) the millions world-wide, you'd think that there would be plenty of demand for named cultivars. Instead, they are rare. The flowers of J. mimosifolia 'Alba' are pure white; it is probably similar to 'White Christmas', which is available in Australia. One source mentions a form with variegated foliage, but only en passant. I can't locate a source for either. At present, then, only the species is readily available. Seeds germinate easily, so expect some variance. Even better, propagate the more interesting forms via cuttings or grafting, then provide cultivar names and bring them into commerce.

 

The flowers of J. jasminoides are a thrilling dusky plum. This species, known as dwarf jacaranda, can mature as a large shrub or small tree. It is a precocious bloomer, and can begin flowering while only a foot or two high. It's on my wish list. The flowers of J. cuspidata are darker still, a true violet.

Availability

On-line and, where hardy, at retailers.

Propagation

By seed, cuttings, and grafting. Seed-grown plants can be slower to begin flowering, but my young container-grown specimens certainly didn't receive that memo.

Native habitat

Jacaranda mimosifolia is native to Bolivia and Argentina.

 
 
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