Book Review: Michael Dirr's Viburnums

by Susan

Who is this guy?
First, a word about the author, because the name Dirr carries a lot of weight in the plant world.  This Georgia professor of horticulture has authored 12 books, which seem to become instant classics.  But I like that his stature hasn't stifled his inner ranter, and he gets quoted for assertions like: "A garden without viburnums is like a life without the pleasures of music and art."  See, a passionate guy, and that passion and a nice sense of humor are reflected in his writing.  Here's lots more about him.

The book
The challenge faced by Dirr and Timber Press was to produce the definitive book about a large genus of plants that pleases several groups - home gardeners, nursery professionals and garden designers.  Well, this home gardener loved the 424 excellent photos of every species that's profiled, and more advanced readers are treated to detailed breeding notes and other hort arcana, so the result is not a read-through garden narrative but a true reference book.

Putting on my coaching hat, I imagined gardeners consulting the book for advice about the right plant to buy, maybe one that's especially shade- or drought-tolerant, hardy to Zone 4, or most likely to be available on the market, and here the book might disappoint.  The narrative format of the plant profiles requires a whole lot of reading to cull answers like those, and this impatient reader would have preferred little symbols or some easy way to hone in on plants that meet particular requirements.

Viburnums
It's a big ole genus of plants that come in a wide variety of sizes, some evergreen, mostly drought-tolerant, largely free of diseases, with a "strong trend toward deer resistance", offering both American natives and nonnatives to choose from, so what's not to love?  Exactly - so why is it so little used?  I've noticed a handful at the largest nursery near me, at the end of bin after bin of rhodies, a plant group that's much less likely to perform well in Mid-Atlantic gardens. 

Dirr's on a mission to correct the underutilization of these tough but beautiful shrubs, the next logical move in his campaign for woodies as a whole.  As a consistent, possibly annoying cheerleader for shrubs myself, I salute him!

Naturally I read the plant profiles for plants I've grown myself, and about V. carlesii or Koreanspice Viburnum, Dirr says it does indeed live up to its catalog descriptions, then goes on to the details.  That reality check is what I want in a plant book - that and great photos - and this book delivers on both counts.

Both the snowball and doublefile types of V. plicatum are considered by many to be the most gorgeous of all, but I learned recently from an expert near me that they're the least drought-tolerant of all Viburnums.  Wish I'd known that before I bought up a bunch of them because the Great Drought of 2007 caused mine to suffer quite openly.  So I was curious to see if Dirr mentioned this and he didn't disappoint, stating that "consistent drought and high heat result in bedraggled specimens."  Yes, bedraggled is a good word.  But the point is that Dirr gives readers that in-the-garden reality check.

Care - What I learned

• When examining a potted specimen at the nursery, slip it from the pot and check the roots - the more white roots the better.  I did not know that.
• As to pruning, Dirr says that "tidying and shaping with hand pruners is best."  Plus, you can shorten (to the nodes) any extended shoots.  In hedges, he recommends against using hedge sheers (brown edges can result).  Instead, do "feather pruning with a hand pruner".  This approach "involves removal of every other shoot, every other year" but "results in a more aesthetic, not-as-blocky hedge."  Never heard of such a thing.  Will try it.
• As to fertilizing, Dirr says that Viburnums "prosper quite well on a restricted fertilization diet".  He feeds his in late winter with the recommended rate of 10-10-10 plus minor elements.  "A second application, (one-half recommended rate) can be applied after flowering."  Now that wouldn't be my definition of restricted fertilization diet.  I'm more of the mulch-them-and-they-will-thrive school.
• Which fertilizer to use?  "Slow-release fertilizers like Osmocote (The Scotts Company) and Nutricote (Sun Gro Horticulture) are suitable as well, or water-soluble formulations like Miracle-Gro, also from The Scotts Company," with their website URL given.  What, no thoughts about whether to use fast-and-synthetic or slow-and-organic?
• I was happy to see this: "Soils enriched with rotted and composted manure and other organic materials provide ideal havens for viburnums and reduce the need for supplemental fertilizer," and he recommends mulches of composted leaves. So I'm pretty sure he gardens like we do - naturally.

Plant Variability
Here's proof that nothing's a given in the wild world of plants.  V. nudum 'Winterthur' is labeled as growing to 6' and that proved to be the case in Dirr's garden (after he killed the first one he tried, and I love that honesty).  But a 'Winterthur' at Longwood Gardens grew to 10'.  The doublefile 'Shasta' matures at 6' in some places and 12' in others.  Keeps us on our toes.

Questions I Have

• In his acknowlegments Dirr thanked some folks for "making me spiritually and academically whole and persistent."  Now that sounds like the beginning of an article I'd love to see published somewhere.  Say more!
• What does Zone 7(8) mean, or conversely, (4)5?  Sorry if I'm showing my ignorance but I couldn't find an explanation.
• And about V. nudum Dirr writes that it's "native to Connecticut, Long Island to Florida, west to Kentucy Lousisiana, and east Texas.  Zones 5 to 9. Introduced in 1752."  If it's native, what does "introduced" mean?  Again, my apologies.

So I pick some nits - that's what I do - but they pale in comparison to my admiration for this valuable contribution to garden writing, and the author and publisher who consistently produce such good work.

Photos from top: cover art from Timber Press, close-up of V. plicatum snowball-type, long view of V. plicatum 'Shasta', and close-up of V. nudum 'Winterthur'.

Comments

[Terry]

Just a quick note to Rant readers in the northeast, Viburnum Leaf Beetle (VLB) can do a number on a range of native and introduced viburnums. Cornell University has an excellent "Citizen Science" website devoted to this critter - including some amazing video of a female laying eggs, eggs hatching, and adults feeding. The link is http://www.hort.cornell.edu/vlb/.

[Gloria]

Dirr most likely means introduced to cultivation. Even natives were/are investigated before recommendation to the horticultural community. That long ago north america was a treasure trove of new species.

Zone range may be site specific. An open windy plain will be different than an enclosed protected area. A valley sometimes freezes as cold air sinks...etc.

Also some individual plants are suprisingly adaptive.
Dirr states that Viburnum rufidulum a southern Blackhaw has a cultivar 'Emerald Charm' that has withstood to -20 degrees F at the Morton Arboretum near Chicago in Illinois.

I just picked up 'Viburnums' yesterday. Reading about every single plant for information is not a problem here.Last night I skimmed over and looked at pictures but will savory each one before I'm finished.

[george]

i put in a viburnum bodnantense 'Dawn' this spring. and wow. it just started blooming about two weeks ago, and is probably going to hit its peak in another 2 weeks.

what a great looking plant. very fragrant. its kicking all the other plant's butts for "winter interest" right now.

so yea, GO VIBURNUMS!

[John]

> What does Zone 7(8) mean, or conversely, (4)5? [...]

The numbers in parens likely indicate borderline or possible hardiness zones.

> "native to Connecticut [...] Introduced in 1752." If it's native, what does "introduced" mean? [...]

This refers to the year the plant was introduced into horticulture/gardens.

[Don Boekelheide]

Thanks for the review of Dirr, Susan.

John and Terry already answered your questions, but I just wanted to chime in in praise of Dirr (and woodies). I've about worn out his _Manual of Woody Landscape Plants_, the one with the plain brown cover, and the line "A garden without a viburnum is akin to life without music and art."

In all the nurseries I like, I almost always spot a copy of Dirr tucked away behind the counter, tattered, mudstained, and flapping with sticky notes, just like mine. As a veggie gardener trained to grow food, I couldn't get by without Dirr.

I'm a fan of using natives whenever possible, but have to admit that Chindo (see Dirr, it is probably V. awabuki - it is the one J.C. Ralston brought back from Chindo Island, Korea) really has done a fine job in a challenging role we've all had to ask of plants in one garden or another - blocking a viewscape of ugly trash cans you can't move. In our case, they belong to our otherwise delightful neighbors.

The chindos are handsome, thriving plants at least 5 m tall here in Charlotte NC, which recently "moved" from Zone 7 to Zone 8. Dirr was right, chindos do appear to need a pollinator to get lots of berries (mine don't produce at all, in sharp contast to, say, deciduous (but who cares?) winterberry holly (Ilex verticillata)). On the other hand, the chindos, which are evergreens, show no sign of the foliage burn from cold he warns about.

But let me second your motion, Dirr's most often right. Excellent review of a good guy, thanks!

[RENEGADE GARDENER]

When it comes to trees and shrubs, Dirr is the Man. "Dirr's Hardy Trees and Shrubs" is possibly my most worn out reference book. Finest photography you will find in a plant reference book. Essential.

Nice guy with a twinkle in his eye and in his prose. Some of my favorite Dirrs:

"In all my traveling and consulting work, I have never recommended, at least when conscious, a poplar."

About Dwarf Flowering Almond: "A small, wispy shrub with essentially no redeeming characteristics other than its double, rose-pink flowers that cover the naked branches in April and May. After flowering, the plant is so bland that it practically disappears until the next flowering season."

The Bardford Pear: "As common as mud in landscapes across the United States. ('Bradford') suffers from a fatal genetic flaw that causes it to self-destruct, literally falling apart with time ... to plant entire streets with this cultivar is playing biological Russian roulette."

Amorpha fruticosa: "My first encounter with this shrub provided convincing evidence that I would never use it in the garden."

I should point out, ninety-nine times out of one hundred, he gushes equally delightful praise.

Dirr played a key role in the introductions of Clethra alnifolia 'Ruby Spice' (the only Clethra in my Zone 4 garden that's worth a damn) and the famed (infamous?) Endless Summer Hydrangea.

Thanks for the tip about the book, I'll probably pick it up, even though Minnesota/Zone 4 supports less than a handful of truly dazzling Viburnum varieties; most of the killer, newer varieties kick in around Zone 6.

RENEGADE GARDENER

[Marte]

Don, which viburnums are dazzling in zone 4?

[Kim]

Susan, what a great review. I was glad to see that I'm not the only one who fell in love with the doublefile viburnum before I found out that it isn't nearly as drought-tolerant as I'd thought. I keep trying to find mine a good home in my Mom's relatively moister ground... but if I don't find a good home for it, it may have to stay in my yard. This is one plant I just can't seem to bring myself to shovel prune.

[RENEGADE GARDENER]

Marte, my favorite viburnums for the north are:

Blackhaw (V. prunifolium) - Z3, dark green foliage goes red & bronze in fall, white flower clusters in spring, attractive, edible bluish black fruit in fall. 12-15' H x 8'-12 W.

V. dentatum 'Christom' (Blue Muffin) - Z3, lotsa white flower clusters in spring followed by lotsa very blue berries that you can see a block away. Goes yellow-red in fall. Good for foundation plantings because of its 4-5' H x 5' W.

V. sargentii 'Chiquita' - Z3, very showy white pinwheel-like blooms with purple stamens, rich red fruit stands out, very nice yellow-orange fall color, 5-6 H x 5-6' W.

V. sargentii 'Onondaga' - Z4, striking maroon foliage as leaves appear, maturing to green with maroon tinge by July. White flowers tinged with purple, red fruit and foliage for fall. 6-8' H x 6-8' W.

V. trilobum 'J.N. Select' (Redwing) was a new intro this spring and I haven't used it, but will if it performs as advertised, Z4, red-tinged new growth, flat-topped white flower clusters, dark green foliage, red in fall, bright red berries hold well after leaf drop, 8-12' H x 8-12' W.

V. trilobum is highbush cranberry.

Witherod (V. cassinoides) - Z3, emerging leaves are purple-tinted—sometimes—but this is stellar in fall, leaves go orange-red-purple. Same old creamy white flowers but the green fruit turns red, then blue, then black, then the birds eat it or you track it into the house. 7-10' H x 6-8' W.

If I could only grow one compact viburnum I'd grow Chiquita although only Onandaga has flowers like you'll see in the cheater zones. For a big one I'd do Blackhaw (also available in lovely small tree form).

Remember, "dazzling" is in the eye of the beholder. These viburnums don't have the leaf variations you get with certain Z5/6 varieties, the cool long slender leaves, shiny, rugose, etc. And we don't get the massive flower displays you'll see in the PNW because, you know, the thing got cold. But we can more than hold our own for fall color.

This is another plant that books and nurseries say "Full sun to part shade" but I don't think they're worth planting—talking about in the North now—unless you plant in full sun. Fall color is greatly diminished in anything less, as is flowering and fruiting. Probably do better in part shade in Z7, I've seen them in some pretty shady woodland settings around Portland & Seattle where the flowers were outstanding.

Should mention for Ranters in Flin Flon, Manitoba, there are three Z2 Viburnums in the trade, V. trilobum 'Bailey Compact' and 'Hahs' plus V. lentago (Nannyberry). All good fall color, flowers, fruit, whole deal. Google 'em, or buy the book, they are in there I'm sure.

Last time you'll ask me a question, I know, Marte.

[Marte]

Thanks very much for all the great info! By the way, "Perennials for Northern Gardens" has been invaluable to me. Thanks for that too.

[layanee]

I am another Dirr fan and proudly own several of his books. I will have to add 'Viburnums' to the collection. His book on 'Hydrangeas' is equally informative but the bible has already been mentioned, 'Manual of Woody Plants'! A standard in plant identification classes. Dirr's 'Hardy Trees and Shrubs' may be more user friendly with its' glossy pictures and is worth consideration also!

[Donna Moramarco]

Mike spoke at a green industry program that I co-chaired on LI this past October. One of his talks was on Viburnums. Lucky for us his book had just been released! His other two talks that day were on Hydrangeas, Noble Plants. I've had the privilege of knowing Mike for many years. If you ever have the chance to hear him speak - you must - he is an absolutely fabulous speaker. Imagine his books - spoken to you. I always say "In Dirr, we trust."