Let’s be rational about roots

One of my colleagues alerted me to a blog post on tree myths currently making the rounds on social media. As a myth debunker myself I was particularly intrigued by the last myth “Root Pruning Stimulates Root Branching:”

“When planting a tree’s root ball, It is very tempting to cut back on roots that are circling the ball. It is very often thought that a dense root ball will stimulate new feeder root growth…but that is not the case.

“Don’t worry about encircling roots as they will correct that on a new site.

(Yeah right)

“Most new root growth occurs at the end of existing roots. Root pruning is often done at the nursery to accommodate packaging and to resume growth before the final sale. If you are planting the tree at its final site, it may be best that you gently break up the root ball but never prune root tips.”

Most surprising of all was the statement at the end of the post which cited an Extension publication by Dr. Ed Gilman at the University of Florida.

Let’s straighten this out (pun intended).

First of all, root pruning DOES stimulate new root growth. It’s just like the response you see when you prune the crown of a plant – the buds below the cut become active and develop into new shoots. There are growing points behind the cut ends of roots which act in the same manner.

Young root branching

Second, circling roots will NOT correct themselves after planting. If they are flexible, you can tease them out to radiate from the trunk. If they are woody, you will have the same luck straightening them as you would in straightening a dowel. If anything, it’s going to break. Not bend.

Seriously. You think this root is going to straighten out?

Finally, root elongation (growth) DOES occur at the end of existing roots – IF they are intact. If they’ve been cut, then we’re back to my first point.

This is basic plant physiology. The response of roots to pruning has been known for several decades. So how could the University of Florida publication be so wrong?

Excessively long roots can easily and safely be pruned before planting

I was able to track down the publication “Dispelling Misperceptions About Trees“. It was written in 1991 and has since been archived – meaning that it’s not considered to be a current source of information any longer. But let’s take a look at what it says, especially the underlined portion:

 Root pruning does not stimulate root branching all the way back to the trunk. Roots are often pruned before moving a tree in hopes of creating a denser root ball.However most root growth after root pruning occurs at the end of the root just behind the root pruning cut, not back toward the trunk. Therefore, dig the root ball of a recently root pruned tree several inches beyond the location of the root pruning. Root pruning should be conducted 6 to 10 weeks before moving the tree. Root pruning more than 10 weeks before moving the tree will reduce the advantages of pruning, because regenerated roots will quickly grow outside of the root ball.”

Root pruning when these trees were dug results in many new flexible roots

This says exactly what I stated in my first point: root pruning stimulates new root growth – which is root branching.

Dr. Gilman’s document goes on to say:

“Roots circling around a container do not continue to grow in a circle once the tree is planted in the landscape. Roots frequently circle within the perimeter of a container several times before the tree is planted into the landscape. The portion of the root which grew in the container does not straighten out, but new growth on this root will not continue to circle.”

So yes! You DO need to worry about those circling roots!

Circling roots turned this crape myrtle into a crap myrtle (Courtesy of Roger Duvall)

In 1991 Ed was an assistant professor at UF and went on to write hundreds of Extension publications and research articles during his career. And in 1991 he was well aware of how root pruning affects root growth.

The moral to this story: read your sources carefully and cite them accurately. And if what you read doesn’t jibe with the current state of science, ask questions!

What’s in YOUR honey? It may not be the nectar you expected.

This month’s National Geographic has a brief article from an ongoing study of the DNA profiles of urban honey. While we can all observe honeybees visiting flowers in our own gardens, until recently we could only assume what nectar they were collecting for honey production. This tantalizing snippet completely blew me away.

Honey collection

The study, undertaken by an entomologist who founded the Urban Beekeeping Laboratory and Bee Sanctuary, is sampling urban hives from major cities, including Boston, Portland (OR), New York, San Francisco, Seattle, and Washington DC. For each of these cities, National Geographic reports the top three plants for honeybees based on relative DNA levels.

Here’s what I found amazing about this research:

      • The top sugar sources are from TREES. Not wildflowers. We don’t see bees visiting trees as easily as we see them visiting flowers, so our perceptions are biased. Over 75% of the sugar used for urban honey is from trees.

        Honeybee visiting flowering tree
      • The trees that are most popular for bee visitation are not necessarily native to those regions. Seattle bees, for instance, prefer linden and cypress trees, neither of which are part of the native coniferous forest. Likewise, the despised eucalyptus trees of San Francisco are one of the top three sugar sources.

        Flowers and leaves of linden
    • You’ll notice that I didn’t use the word “nectar” in describing what bees are collecting. That’s because much of the sugar they are gleaning isn’t coming from flowers. It’s coming from sap-sucking insects like aphids that produce honeydew. Bees apparently collect honeydew as well as floral nectar.

      Aphids!
    • Urban areas usually have higher plant diversity than rural areas, given the variety of woody and herbaceous plants that people use in their gardens and landscapes. The researchers speculate that this higher plant diversity may be one reason that urban hives are healthier and more productive than rural ones.

      Garden beehive

Many gardeners operate under the assumption that native plants are the best choice for gardens and landscapes. Though certain landscapes (like those undergoing ecological restoration) should only be planted with natives, there is no evidence-based reason that we shouldn’t be using non-invasive, introduced species as part of our planting palette.  In fact, research has demonstrated that tree species nativity plays only a minor role in urban landscape biodiversity: most animals learn to use new resources in their environment. Honeybees, considered to be “super-generalists” insects, are demonstrating that in spades.

Upside-down growing

I was poking through old photos and came across this oddity:upsidedowntrees

What you are looking at is Japanese maples (Acer palmatum) being grown hanging upside down. I saw this year ago at a nursery in Japan. (You are also probably looking at a disaster of girdling roots in those tiny plastic pots, but that’s another topic) When I asked about them, I was told that they are weeping forms, and grown this way temporarily before being planted in the ground right-side up.
Looking at the image, it makes me think that the particular variety grown here might have a mutation that makes them negatively gravitropic, and so respond to the pull of gravity in the opposite way a normal plant would. (For more on that see my earlier post on gravitropism in corn) Growing them upside down would allow them to produce a fairly normal branching pattern, and then once plants, new growth would, presumably, cascade down from the established trunk and stem.
Anyway. That’s your oddity for the day.
Joseph Tychonievich

Trash or Treasure?

You’ve probably heard certain plants dismissed as “trashy” –  but what does that mean?  We have a delightful Magnolia macrophyla in our campus garden – with huge foliage, creamy blooms, the native factor, etc., it draws all kind of attention. So I’d hesitate to call it trashy. But the autumn leaf drop clutters the ground with leaves the size of a sheet of legal paper.  They aren’t rake-able, or really mow-able, have to gather by hand into “sheaves”.  And there’s a LOT of them.

Here’s another example:

We plopped a 3-gallon Koelreuteria bipinnata (many common names, such as Chinese Flame Tree, Bougainvillea Golden Rain Tree, etc). into one of our home perennial borders a few years ago. As Dirr notes, it started out “beanpole-like in youth” but has grown into a nice vase shape. It hit puberty last year, with a smattering of flowers and fruit. This year has been a different story – I swear it doubled in size; and judge for yourself its full-on adulthood:

KPblooms

Late August and early September brought huge panicles of yellow flowers – eye-popping for us, and a late-season bounty of pollen and nectar for our honey bees (and every other bee and wasp in the area). You could hear the canopy “buzzing” from several yards away.

The yellow petals then fell away, carpeting the grass and part of our deck. It their place developed shrimp-pink, papery capsules.

KPpodshabitI cut one of the capsule-filled branches off; and a month later everything is still pink and intact in a vase of water. I also noted each of three capsule sections bears one dark round glossy seed. Uh-oh. That’s a lot of seeds.

KPpodsWith our first freeze, the leaves fell – in big chunks consisting of a tough foot-long petiole and a bunch of leaflets. My mower didn’t do a good job chopping them up – ended up having to rake and move to compost pile. What the mower DID do was fling the papery capsules far into other beds.

KPtrashFlashy? Yes.
Trashy? Yes.
Invasive? Not sure yet. Will report back if seedlings appear!

Comments welcome – tell us about your favorite “trashy treasure”!

A Resilient Citrus Tree Rebounds

Cit3Spring1

Sad Citrus

The last two winters have been pretty brutal on my citrus trees.  Their winter home is the enclosed, but unheated, south facing entrance foyer.  Usually, this is a perfect spot.  Sunny, and with temperatures usually in 45-60 degree range.  But when the polar vortex brought record cold to the Mid Atlantic region back in February, they were hit hard, and I had my doubts that this 13 year old specimen would survive.

Cit3Fall1

Happy Citrus

But it bounced back pretty well, after a season in the sun, so I figured it should be rewarded … I’d give it a new home, replacing its split container … and document the process here.

process1

Prep Area

drill

Drainage Holes Drilled

Process2

Whew! No Pebbles in the Bottom!

Parsley

Rescued Parsley

girdle1

Uh Oh, The Dreaded Circling Root.

girdlecut

Snip Snip

DoneChips

Wood Chip Mulch, of Course

DoneDone

Voila!  Ready to Move Inside

 

Top Ten Trees and Shrubs with Great Fall Color

 

Sugar maple (Acer saccharum) in full fall color
Sugar maple (Acer saccharum) in full fall color

As promised in my Sept. 9 post of “The Science Behind Fall Color”, I would address trees and shrubs with outstanding fall color. It was hard limiting it to only ten trees and ten shrubs, since I found 5 common shrub species of maples alone, so I cheated a bit and grouped the maples, oaks, etc. into one group so that my list was not entirely all maples.

'Robin Hill' apple serviceberry (Amelanchier x grandiflora 'Robin Hill')
‘Robin Hill’ apple serviceberry (Amelanchier x grandiflora ‘Robin Hill’)

I have seen the below plants with reliable fall color in northern, southern and eastern landscapes. These plants “light” up the landscape in autumn. For outstanding, long lasting autumn color, plant the below trees and shrubs with herbaceous plants which bloom in fall such as asters, mums, sedums, monkshood, toad lilies, and Japanese anemones. Do not forget ornamental grasses with their showy seed heads extending the season of color and texture.

Sweet birch, cherry birch (Betula lenta)
Sweet birch, cherry birch (Betula lenta)

We used to recommend ash for fall color, but not any more due to emerald ash borer. Japanese barberry and burningbush are tops for fall color, but both species are highly invasive and not recommended. There are more plants with great fall color than the ones below. I would love to hear your favorites!

 

Top 10 Trees for Fall Color

1) Black gum, sour gum, tupelo (Nyssa sylvatica), orange-red, scarlet to purple, outstanding

Black gum, sour gum, tupelo (Nyssa sylvatica)
Black gum, sour gum, tupelo (Nyssa sylvatica)

2) Maples, especially:

Sugar maple (Acer saccharum), bright yellow to orange-red

Red maple (A. rubrum), yellow, orange-red to bright red

Freeman maple (A. × freemanii), yellow, orange-red, red to reddish-purple

Paperbark maple (A. griseum), dark red to bronze

Japanese maple (A. palmatum), orange, red to purplish-red

Korean maple (A. pseudosieboldianum), deep orange to reddish-purple

Three-flower maple (A. triflorum), orange

Full moon maple (A. japonicum), yellow-orange to scarlet-red

Moosewood, striped-bark maple (A. pensylvanicum), bright yellow

3) Ginkgo (Ginkgo biloba), bright golden-yellow

4) Thornless honeylocust (Gleditsia triacanthos f. inermis), bright golden-yellow

5) Quaking aspen, trembling aspen (Populus tremuloides), bright yellow

6) Oaks, especially:

White oak (Quercus alba), dark red to wine

Red oak (Q. rubra), red to russet

Scarlet oak (Q. coccinea), red to scarlet

Black oak (Q. velutina), dark red

Scarlet oak (Quercus coccinea)
Scarlet oak (Quercus coccinea)

7) Apple serviceberry (Amelanchier × grandiflora), yellowish-orange to red

8) Buckeyes, especially:

Yellow buckeye (Aesculus flava), golden-yellow to orange

‘Autumn Splendor’ buckeye (A. × arnoldiana ‘Autumn Splendor’), deep, burgundy-red

‘Homestead’ buckeye (A. × marylandica ‘Homestead’), orange-red

9) Birch, especially:

Yellow birch (Betula alleghaniensis), bright yellow

Sweet birch, cherry birch (B. lenta), bright yellow

Paper birch, canoe birch (B. papyrifera), yellow

10) Yellowwood (Cladrastis kentukea), bright yellow to gold

 

Top 10 Shrubs for Fall Color

1) Large and dwarf fothergilla (Fothergilla major and F. gardenia), yellow-orange to red, outstanding

Large fothergilla (Fothergilla major)
Large fothergilla (Fothergilla major)

2) Common and vernal witchhazels (Hamamelis virginiana and H. vernalis), bright yellow to golden-yellow

Vernal witchhazel (Hamamelis vernalis)
Vernal witchhazel (Hamamelis vernalis)

3) Virginia sweetspire (Itea virginica), dark reddish-purple

4) Black and red chokeberries (Aronia melanocarpa and A. arbutifolia), red-orange, wine-red to purple

Black chokeberry (Aronia melanocarpa)
Black chokeberry (Aronia melanocarpa)

5) Sumacs, especially:

Shining sumac, winged sumac (Rhus copallinum), bright red to scarlet

Prairie Flame® shining sumac (Rhus copallinum 'Morton')
Prairie Flame® shining sumac (Rhus copallinum ‘Morton’)

Staghorn sumac (R. typhina), orange to scarlet

Smooth sumac (R. glabra), orange to scarlet-purple

Fragrant sumac (R. aromatica), orange, red to purple

6) Oakleaf hydrangea (Hydrangea quercifolia), reddish-orange to wine

7) ‘Tor’ birchleaf spirea (Spiraea betulifolia ‘Tor’), orange to reddish-purple

8) Viburnums, especially:

Withe-rod viburnum (Viburnum cassinoides), orange-red, crimson to purple

Blackhaw viburnum (V. prunifolium), reddish-purple

Arrowwood viburnum (V. dentatum), depends on cultivar, yellow, red to purple

American cranberrybush viburnum (V. opulus var. americanum, formerly V. trilobum), yellow to reddish-purple

Doublefile viburnum (V. plicatum f. tomentosum), wine-red

‘Wavecrest’ Siebold viburnum (V. sieboldii ‘Wavecrest’), red to burgundy

9) Cranberry cotoneaster (Cotoneaster apiculatus), deep reddish-purple

Cranberry cotoneaster (Cotoneaster apiculatus)
Cranberry cotoneaster (Cotoneaster apiculatus)

10) Virginia rose (Rosa virginiana), deep reddish-purple

 

 

Laura Jull, Ph.D.

a.k.a.: The “Lorax”

Bad power line pruning

Driving home today, I saw this lovely sight:

powerlinepruningOur local utility company has been busy butchering trees around the power lines.

Every plant person I know complains about this, but I honestly don’t think there is much hope for a change. Power companies don’t want limbs falling on the electric cables during storms, and they’re not likely to start spending money to hire real arborists to do the pruning.

What I really wish is that people would start thinking a little more before putting in a tall tree directly under electric lines. I’m sure these went in as cute little babies, I know it can be hard to visualize what a small tree will grow into, but we do really need to do a better job of it. If you are looking to plant, take the time to look up the tree in question and see how fast it is going to grow. Google will usually tell you, and if you are planing conifers, the American Conifer Society has an amazing website which will tell you the growth rates in inches per year of just about any conifer you can imagine. Check it out, and do the math, and see just how fast that little spruce is going to be causing problems before you start digging holes.