Sustainable Gardening Blog

It’s what almost every garden needs and what almost no garden gets.  

RENEWAL PRUNING

Are there any full-grown azaleas, spireas, weigelas or snowball viburnums (V. macrophalem) in your garden?  Then there’s a 99 percent chance that they need renewal pruning and now’s the time to do it.  

First, remove any dead stems and branches.  But that’s just a warm-up.  The real fun is in removing one-third of all the stems all the way to the ground or close to it.  Ah, but which stems to remove?

• Stems that are growing where you don’t want them to grow, like hanging over a walkway or bullying a nearby shrub.
• Stems that are crossing other stems, especially the ones that begin on the outside and grow through the middle, crowding the whole interior of the plant.
• If those two types don’t add up to one-third of the stems, take out the oldest ones next.  Conveniently, these are often the tallest - too tall, in fact.  People are tempted to cut them back a foot or two at the top and the result is even more growth up there where it spoils the shape of the plant.  The plant becomes top-heavy, especially if it has large flowers to hold up, like this snowball-type viburnum.

Almost everyone who hires me has plants that need renewal, so I’ve explained this technique many, many times and people are totally unbelieving.  This type of pruning (the correct kind!) is SO counterintuitive, it takes a total leap of faith to actually try it.  I give my pep talk but after I drive away, who knows?

Readers, give it a try.  I’ll go out on a limb and promise that you can’t kill one of these plants by doing what I’ve suggested. 

HOW TO LEARN TO PRUNE

But what if you have some other shrub that’s not on the list above?  Or say your old azalea is part of a large crowded mess of shrubs and you have no idea how to tackle the problem.  No book or website can really provide the answer, and you’re thinking you might need someone to do it for you - or better yet, teach you how to do it.   Hiring an arborist (or a gardening coach)  to come to your garden, assess the situation, and teach you to take care of your shrubs and small trees for no more than you’d pay for a lawn treatment would be money awfully well spent.  Super-low-maintenance shrub gardens fill out and look great and really are low-maintenance, but not no-maintenance.  Without yearly pruning they become unruly jungles.   Keeping shrubs beautiful, healthy, and the right size for the landscape is SO damn easy, but very few homeowners will give it a try.

Here’s what might help - if just some of the TV segments about "How to create a container garden" were retired to the archives and demonstrations of "How to prune your azaleas" were shown instead.  Hey, I’d even wield the Felcos myself - for the cause.

For years, this has been my favorite shrub for shady spots because of its outstanding
appearance all year long. Long white flowers appear in March and April,
but its evergreen foliage gets lots of attention, too, especially the
new growth that appears in fabulous shades of reds.

Then just this year I started hearing gardening
experts warn that global warming is NOT being
kind to this plant, and one has even stopped recommending it.  Say it
isn’t so!  Maybe now’s a good time to look into similar plants like the
American species and Japanese-American hybrids (more on them below). 

Photo credit.

DETAILS

• The straight species can grow (slowly) to 8 or more feel tall, but many shorter varieties are available.-12 tall )
   

• Hardy to Zones 5-8 Japan.   

• Performs best   in partial shade and acid soil.

CARE

• Pieris has only average drought-tolerance, so needs watering  during dry periods.
• Really requires no pruning but if you do you prune, do it after flowering to avoid cutting off the buds.
• Unless your soil is already acidic, apply Hollytone or other organic fertilizer for acid-soil-loving plants every spring.
• Lacebug is a common and serious pest that sucks the sap from the
  leaves, yellowing them.  Adequate shade, water and soil acidity reduces
  its vulnerability, however.

Photo credit.

PIERIS FLORIBUNDA, AND HYBRIDS OF THE TWO SPECIES

Pieris floribunda, a native plant from Virginia to Georgia, is 2 to
6′ tall, with a greater spread.   It’s harder to propagate so, not
surprisingly, it’s not as available as the Japanese species.  Woody plant expert Michael Dirr reports learning that the natives
consistently die out in the Atlanta area but that hybrids (crossed with
the Japanese species) do just fine there.      

UPDATE:
I’ve taken the question of invasiveness to the expert for HIM to figure it all out, and I’ll post his findings right here.
 

Where it isn’t an *invasive pest, Nandina is valued for its extreme tolerance of drought, its tolerance for sun or deep shade, its evergreen foliage, and the red berries that, when eaten by birds, are causing problems in the Southeast. (Photographed here with Aesculus parviflora or bottlebrush buckeye.)

Invasive?

Nandina domestica is on the invasive plant lists for Texas and the Southeast, as far north as Virginia, where it spreads by bird-carried seeds.   Yet I’ve read warnings from  naturalists that nandinas aren’t, in fact, food for birds (so shouldn’t be counted as wildlife-friendly).  So the unsolved mystery is:  Are there noninvasive varieties of nandina whose berries the birds won’t eat? They also spread very occasionally by stolens in a clumping manner, but that’s not been pinpointed as the problem - only the dropping of seeds by birds.

But just to complicate the issue even further, the former president of the Florida Native Plant Society has written publicly that Nandina was designated as invasive in Florida by the very groups who benefited from doing so (by receiving more funds for its removal).  He disagreed with that designation and quit the Society in protest.  Yikes.

In any event, some gardeners who grow Nandina prevent the production of berries and the possibility of spreading by removing its flowers.

It’s indigeneous to China and Japan.

Details

• Lacy white panicle-shaped flowers in the spring; bright orange berries emerge and last for months.
• Fine in full sun or deep shade.
• The species grows to 8 x 4-6 feet’, and dwarf varieties are available that are full grown at  3 or 4 feet, even just 2.
• Hardy to Zone 6.
• Deer-resistant.

Care

• Extremely drought-tolerant, meaning that gardeners report its survival through the longest droughts with no supplemental watering at all.
• No insect or disease problems are reported.
• If leggy, the stems can be cut back to the ground.
• May drop leaves if temperatures go below 10 F, or die back to the ground in below-zero temperatures.

Your Comments are Welcome and will be added to the plant profile on Sustainable-Gardening.

Cherry laurels are extremely popular with landscape
designers as evergreen foundation shrubs and hedges, but
they’re less well known to the
public because they’re not showy.  They don’t exactly scream "buy
me" at the nursery.

The ‘Otto Luyken’ and ‘Schip’ laurels are the favorites, both of
which I use in my garden - they’re used to hide both the foundation of the house and the under-deck view. And the taller species functions well as an evergreen screening hedge
along my side property line.  But don’t miss the pruning ideas below.

In the U.S. they’re often referred to as "English laurels;" in England, not surprisingly, just "cherry laurels."  They’re indigenous to Eastern
Europe and Asia Minor.

DETAILS

• All varieties do well in full sun or partial shade, and
  ‘Otto Luyken’ even tolerates deep shade.
• White blooms appear mid-spring
• Size? Take your pick.
  • The species (photo right) grows fast (up to 2′ per year) to 20 feet tall, if
    left unpruned.
  • ‘Otto Luyken’ grows to 3-4 feet tall and 6-8 feet wide.  It’s shown in the
    top photo.
  • ‘Schipkaensis’ or ‘Schip’ (photo below) grows to 4-5 feet tall and 5-8 feet
    wide.
• Sources say they need good drainage,  but doesn’t almost every plant?
• Hardy to Zone 6.

CARE

• One less-than-helpful source tells us to "water regularly". In my
  experiencethey’re quite drought-tolerant, once established in the garden
  (after at least the first season).
• To prune for smaller size, cut the tallest stems back to varying heights,
  but always just above another branch (don’t leave stumps). OR remove the tallest
  one-third of the stems all the way to
  the ground or close to it every year.

• Left unpruned, cherry laurels can become so thick and densely branched that
  light and air are restricted and disease and pest infestations are encouraged. 
  So keep them more open and healthy by removing some of the interior branches,
  especially ones growing toward the center.
• Don’t prune by sheering around the edges to a perfect but unnatural
  shape - this will lead to the same dead interior problems described above
  (disease, pests).

Readers, if you’ve grown these, do what’s been your experience with them?

Here’s a plant we think of as too formal, too boring, too (fill in the blank).  But I suspect our criticisms of boxwoods are based primarily on the way they’re traditionally grown - pruned to soldierly uniformity, despite the less than robust good health enjoyed by plants thus brutalized by shearers.  (The poor plants must whimper in dread when they see gardeners approaching with the damn things.)

So I offer an alternative - the Natural Boxwood.  Here are two ‘Green Ice’  boxwoods I planted smack dab in front of my front porch, replacing the existing (and hideously misplaced) large azaleas in this brutal southwest exposure.  Here’s what the tag says: "Buxus x ‘Green Ice’ - deep glossy green foliage that maintains its color throughout winter.  A solid, semi-compact plant with vigorous new growth.  Extremely hardy.  A soft and sturdy plant."  And it’s proven to be all of that.  Boxwoods even tolerate significant amounts of shade.  And do I need to remind the reader it’s EVERGREEN?  No, I didn’t think so.  On the right is a Spirea ‘Goldmound’, sporting chartreuse foliage all season and brassy fuchsia flowers in June.

The key to natural boxwood growth is to stop shearing and start thinning.  Removing some of the extra thickness keeps the plant nice and open so that more air, light and rainwater can reach the plant’s interior.  The correct pruning technique is often referred to as punching holes in the foliage but if done right, you’d never know that little green globs have been removed because the plant still looks so natural, so unpruned.  The best pruning is unnoticeable, a standard that unfortunately can’t be met when corrective pruning is finally undertaken after years of mispruning or a total lack thereof.  In those cases the natural look can’t be achieved immediately but will follow, in time.  Yet another lesson in patience.

I’m hoping to convince Elizabeth Doyle (of the Yankee Clippers) to create a how-to video on the subject of shrub pruning because she’s a full-time professional pruner and a proven public speaker to boot!  Update to follow.

This Spirea ‘Anthony Waterer’ is TOTALLY rewarding me for removing its dead flowers in late June or so.  Elsewhere in the garden and going unphotographed, the one that escaped my Felcos has zilch in the rebloom department.  You’d think I’d learn.

And because I never tire of shrub photos, here’s a close-up.  Awfully nice in mid-September when there’s nothing but the sedums making a show in my garden.

Michele Owens at SignoftheShovel is, I know, a fine person, not to mention one of the most talented writers in all of blogdom.  But when she leaves this comment on my post about wiegelias, "Nice alternative to those ratty-looking spireas," I want to say - Hey, that’s my Favorite Shrub for Sun you’re talking about there - and rush to their rescue.  I know you all understand. 

So I present the lovely spirea ‘Snowmound’ to make the case for the not-rattiness of spireas.  It’s similar to but possibly even prettier than the popular ‘Bridal Wreath,’  and here it is full-grown.  The only pruning I’ve done is my usual limbing up to remove branches lying on the ground.  All my other spireas are pruned regularly to make them smaller and they respond very nicely with fullness and good form.  I hope to present more evidence shortly.

And for inquiring readers, here’s everything I can think of about spireas.  They come in a variety of sizes, this being the largest, require a half-day of sun to bloom, are drought-tolerant, deciduous, and can be cut back after flowering for a nice second show.  Blooms are white or shades of pink, and there’s even foliage colors to choose from.  See the gorgeous chartreuse of ‘Ogon,‘ a new spirea that’s oh, so popular with designers.  And if any of this is incorrect or incomplete,  do let me know.

AZALEAS. A few quickies today, beginning with a report from the Azalea Belt. Washington Post writer Joel Lerner recently ventured to suggest that azaleas be used only as accents, a bit of heresy I venture to agree with.  This photo and a previous one - scroll down 3 posts - illustrate that excellent point.  Joel also urges readers to resist buying one each of every color and instead stick with just one color.  And if I ever find an example of that, I’m sure I’ll prefer it, too.

Before I leave the subject, I know someone will ask why I think azaleas should be used sparingly, so let me answer that up front.  Because they’re A, overused, even in such inhospitable spots as full sun; B, rarely pruned correctly, if at all; and C, add so little to the garden after their two weeks of glory.  For all those reasons and surely more, dissing azaleas has become common sport among garden designers, even as homeowners cling to their beloved mounds of fuchsia.

ON FAME.  Readers of Garden Design Magazine will find an article and photo spread in this month’s issue about none other than Susan Harris.  Ooh, could that be Takoma Gardener? Well, as my mother would say when someone asked if the famous television writer and producer was her daughter, "no, unfortunately." So I’ve been "not the famous one" for my whole adult life and I’ve been fine with that, although surely my mother would have preferred I’d given her better bragging rights at her weekly bridge game.  But now I learn that the fabulously rich television Susan Harris and her equally successful husband have one of the most beautiful gardens that money can buy.  And thanks, Garden Design, for rubbing my nose in it. 

INDIGNITIES. I was doing some plant rearranging yesterday, performing slight redesigns in practically every border, and feeling totally in the zone.  Visions of greater and greater beauty filled my thoughts - until a big splat of mourning dove shit landed on my scalp.  Suddenly out of the zone, I was comforted by the thought that even the famous Susan Harris could experience birds shitting on her head.  But my next indignity was the kind that only true dirty-fingernail gardeners experience.  It was in my attempt to divide an overgrown ornamental grass and failing with almost every tool in my well-stocked tool shed that I found myself literally wrestling with the damn thing, and losing.  I suppose the the lesson is to divide sooner or enlist neighbors to help.  Or just do what television producers do - write regular checks to the gardening service.

Next in the parade of Shrubs I Love is a weigelia or weigela - spellings differ so whichever you use, people who know better will correct you. I’m hoping someone will tell me which is correct just for the record but honestly, it’s so damn lovely right now I don’t really care.  And why settle for one photo when I’ve downloaded about a dozen?

Since you guys have been patiently teaching me what you want to know about the plants I feature, I’ll start with my notes but feel free to ask questions - I know you will.

Hardy to Zone 5, this and other weigelias need a half-day or more of sun, bloom in late spring and this ‘White Knight’ at maturity is now 4′ tall and 8′ wide.  Definitely drought-tolerant, and requiring minimal pruning.  After six years now, the only pruning it’s received is a little limbing up to keep it off the groundcover.  It just naturally has this lovely arching form.  My pruning book tells me I may eventually have to remove old canes to the ground to rejuvenate it, like I’ve done with the old 10-foot-tall common weigelias that conveyed with my property, a process that worked really well because they grow back so quickly.  And though this one hasn’t needed it, =-generally right after flowering is a good time to thin stems or to cut back "untidy shoots" by half, "keeping the habit of the plant."  Damn right I want to keep the habit.

Bottom line, if this isn’t a high-impact, low-maintenance plant, I don’t know what is.