No Leaves, No Problem: All You Need Is A Twig — Tree Identification in Winter

By Wendy Diaz EMGV

If you are hiking in the forest this winter or even ‘intentionally walking your own yard’ (recent post on https://durhammastergardeners.com) and want to identify a tree, the best way to identify the species in the wintertime is to use the morphological features of the tree that botanists utilize. To start with, all you need is a twig! 

I recently attended a Tree Identification In Winter Workshop by Matt Jones, Extension Agent, Horticulture at the Chatham County Center in Pittsboro where I was introduced to such precise methods and I practiced identifying twigs using the ‘tools of the trade’1.  To differentiate between character traits of tree species one can use the North Carolina State University (NCSU) Dichotomous Key (Key) developed by Dr. Alexander Krings for our particular geographical region of the Piedmont2. Dichotomous keys start by presenting the user with two sets of plant characteristics in a couplet form, then the user has to select one of the two choices, which more accurately describes the specimen in hand1. The user’s choice leads them to the next couplet and so on until they reach a species name and there are no more choices to make. The Key gives the species name in Latin to avoid confusion from the many common names a tree species can have. An easy way to obtain the common name if you are not familiar with the Latin species name is to use the online NCSU Plant Toolbox3.

The features of the tree which are visible in winter and which are most diagnostic of each species are based on the woody plant morphology which does not include the bark of the tree. Bark can be diagnostic for some trees with very pronounced characteristics like the smooth bark of a beech (Fagus grandiflora) for example but depending on the age of the tree or the position of the bark on the trunk, different bark texture may be observed on the same tree which can lead to confusion and it is not always diagnostic. For the typically difficult genus Quercus or oak, it also helps to look for acorns around the base of the tree as the acorn’s morphological features can differentiate between species.

The main morphological features included in the Key are the following: the arrangement and position of buds, bud scales, arrangement of leaf scars, pith anatomy, number of vascular bundle scars, stipular scars and armament. A hand lens, a set of pruners and a bright area to work in will also help in discerning these relatively small species-specific character traits on the twig. It is essential that the user know the vocabulary4 of the Key, such as but not limited to:

Petiole – The stalk that joins the leaf to the stem.

Alternate – The arrangement is at alternating points from one side of the stem to the other or staggered.

Opposite – The arrangement is on the same spot on stem but on opposite sides of the stem.

Leaf scar – A visible thickened crescent mark on stem where the leaf was attached.

Pith Anatomy: The core of the stem can be homogenous (solid and uniform), diaphragmed (sections), chambered (hollow sections) or excavated (hollowed out).

Diaphragmed: Horizontal breaks in the core of the stem and each section is filled with material.

Bud scale:  A modified leaf that forms a protective covering over the bud.

Valvate bud scale: The scale forms two parts of the coating like a clamshell. 

Bud Scale Scar: The concentric rings formed by bud scales from the previous year’s terminal bud.

Stipular scars: A pair of appendages found on many leaves where the petiole meets the stem, tiny and attached around the stem and can be slit-like or ring-like.

To practice my newly acquired knowledge, I cut a small twig from a tree in my front yard and brought it inside with, to my surprise, a caterpillar.

Twig of tree (3 cm diameter) Photo by Wendy Diaz on January 25, 2020
Caterpillar on tree twig. Photo by Wendy Diaz January 25, 2020

The first step was to determine to which structural group the tree belongs by deciding if the leaf scars were alternate or opposite.  The leaf scars were alternate .

Black arrows–alternate arrangement of leaf scars. Grey arrow-encircling stipular scar.
Photo by Wendy Diaz January 25, 2020

For the second step, the stem had to be sliced longitudally so it’s pith anatomy could be examined. The second couplet asked if the pith was chambered/diaphragmed or homogeneous. The pith of this stem was diaphragmed so the next step using the Key was to proceed to Group 2 where the couplet asked if the stipular scars were encircling the twig or if they were absent.  

Diaphragmed pith anatomy with horizontal breaks in the core of the stem with each section is filled with material. Photo by Wendy Diaz January 25, 2020

The stipular scars were clearly encircling the twig so that lead to the next couplet.

Green arrow – valvate but (two parts). Gray arrow – stipular scar encircling the stem. Photo by Wendy Diaz January 25, 2020

This couplet described the bud as either cap-like and pointed apex or valvate and rounded apex.  These buds were valvate (two parts) with a rounded apex guiding me to the final lead, which is the species name of Liriodendron tulipifera or Tulip Poplar!

Liriodendron tulipifera or Tulip Poplar photo by Wendy Diaz January 31, 2020

The NCSU Dichotomous Key can be a little daunting if you are not a botanist, especially if the tree species you are trying to identify requires multiple couplets and it is at the end of the Key such as Carpinus caroliniana (American Hornbeam). I found clicking on the + symbol next to each couplet, which links to a photo of an example image, is a great visual aid and helped me on whether or not to continue on to the next couplet or backtrack. Practice makes perfect, but if you get frustrated with the Dichotomous Key, you can always wait for spring and the leaves to come out or identify your trees with leaves by attending the companion workshop offered by Matt Jones in September 5.

References:

1. https://extensiongardener.ces.ncsu.edu/2020/01/key-2020-winter-state-news/?src=rss

Online tool: NCSU Botanist’s Little Helper: 2.         https://projects.ncsu.edu/cals/plantbiology/ncsc/TwigID/

Online tool: NCSU Plant Toolbox: 3.         https://plants.ces.ncsu.edu

4. https://content.ces.ncsu.edu/extension-gardener-handbook/glossary

5. https://chatham.ces.ncsu.edu/native-tree-identification/

Book References:

Terminology: Plant Identification Terminology An Illustrated Glossary James G. Harris Melinda Woolf Harris second edition

Advanced reference: Woody Plants of the Southeastern United States: A Winter Guide, Ron Lance, University of Georgia Press

Learn With Us, week of February 16

Moss: Primitive and Beautiful – Durham Garden Forum
Tuesday, February 18 7:00 – 8:30pm

Sarah P. Duke Gardens
420 Anderson St, Durham, NC 27708
“Moss: Primitive & Beautiful” with Flora O’Brien, Duke Gardens Volunteer and Extension Master Gardener Volunteer. Moss is a very ancient, primitive plant, and can be enchanting in your garden. It does possess chlorophyll for photosynthesis but does not have flowers or vascular system. Join us to learn more from Flora, the volunteer who cares for the Duke Gardens moss garden.

For any new member joining during the months of February and March 2020, their membership will run through April 30, 2021. Please extend this offer to any of your neighbors, friends, or gardening groups interested in joining the Durham Garden Forum. Our $25.00 membership continues to be an outstanding bargain for the quality of programs/speakers offered. Single program entry fee for non members is $10.00.

Spring Seed Starts
Saturday, February 22 10:00 – 11:00am

Durham Garden Center
4536 Hillsborough Rd, Durham, NC 27705
Description:Starting Seeds for Spring Planting – If you’re hoping to go into the new season with flowers or vegetables or herbs (or all of these), NOW is the time to get both your plan and your supplies together. Topics discussed will include materials needed for successful seed starts; the difference between direct sow and planting indoors; suggestions for proper planting medium; light, water and temperature requirements.

Free/Registration required. Contact:919-384-7526 or http://www.durhamgardencenternc.com

Learn With Us, week of February 9

Getting Started With Warm Season Vegetables
Thursday, February 13⋅3:00 – 5:00pm

721 Foster St, Durham, NC 27701
Description: Growing your own vegetables from seed is a great way to get varieties not commonly found at garden centers. But with so many species and varieties to choose from, it can be hard to know where (or how!) to start. Join Ashley Troth (Extension Agriculture Agent) and the Extension Master Gardener℠ volunteers of Durham County and learn how to get your veggies off to a good start. Participants will learn the basics of warm-season vegetables, including how to select species and varieties, proper growing conditions, and diagnosing common germination and seedling problems.

Click Here for more information and to register

The class costs $6 per person. Registration and fee payment is required by Feb. 11, 2020. Additional classes may be offered if there is sufficient demand. If spaces are full, add your name to the waitlist on the registration page. Workshop will be held at N.C. Cooperative Extension, Durham County Center (721 Foster St, Durham, NC 27701) This class is part of the Bull City Gardener Learning Series and is open to everyone.

Getting Started With Warm Season Vegetables
Saturday, February 15⋅9:30am – 11:30pm

721 Foster St, Durham, NC 27701
Description: Growing your own vegetables from seed is a great way to get varieties not commonly found at garden centers. But with so many species and varieties to choose from, it can be hard to know where (or how!) to start. Join Ashley Troth (Extension Agriculture Agent) and the Extension Master Gardener℠ volunteers of Durham County and learn how to get your veggies off to a good start. Participants will learn the basics of warm-season vegetables, including how to select species and varieties, proper growing conditions, and diagnosing common germination and seedling problems.

Click Here for more information and to register

The class costs $6 per person. Registration and fee payment is required by Feb. 11, 2020. Additional classes may be offered if there is sufficient demand. If spaces are full, add your name to the waitlist on the registration page. Workshop will be held at N.C. Cooperative Extension, Durham County Center (721 Foster St, Durham, NC 27701) This class is part of the Bull City Gardener Learning Series and is open to everyone.

February: To Do in the Garden

by Gary Crispell, EMGV

Welcome to the newly minted month of ‘Febril.’ Seems like we did this last year. Therefore, beware, lest you let your guard down and get caught by the other new month—Maruary which could easily be just around the corner, lurking, waiting to zap your saucer magnolia blossoms and any other non-cold hardy vegetation. And, it ain’t snowed yet neither. So, as tempting as 70 degrees might be, be smart. Just for the record, I didn’t just pull this stuff outta the air. I done researched it like them professors learned me to in Horticulture (yea, I can spell, too)  School on Hillsborough Street in Raleigh. Pay attention, y’all. It’s real stuff.

Lawn Care*

Cool season grasses (i.e. fescue and bluegrass) should be fertilized with a slow-release fertilizer following the recommendation of your SOIL TEST.

Late February/early March is the best time to apply a pre-emergent to prevent crabgrass. There are several easy-to-use granular products on the market. Be sure to read and follow the directions on the label for safe and proper handling and application. Calibrate your spreader to ensure accurate application amounts. Too little will not give you effective control and too much may damage the turf.

Fertilizing

See Lawn Care above and Planting below.

Planting*

And so it begins: the vegetable garden. The reason for existence, for frozen fingers in February, summer sunburn and the endless supply of liniment in the medicine cabinet.

It is time for root vegetables and salad. Vegetables you can plant now include cabbage, carrots, leaf lettuce, onions, potatoes, radishes, rutabagas, spinach and turnips. Work a little fertilizer into the soil that was tested in October (while it was still free to do so) following the recommendations of said SOIL TEST.

Be cognizant of soil moisture levels.  It appears that Mother Nature is going to maintain that for now, but she can be really fickle.

Pruning*
If you have been ignoring previous posts, now would be a good time to prune bunch grapes and fruit trees.

Also due for judicious trimming are summer flowering shrubs and small trees. That list includes crape myrtle (Lagerstroemia species), butterfly bush (Buddleia davidii), and hydrangeas that bloom on new wood (Hydrangea arborescens & H. paniculata). Blueberry bushes will also benefit from a February pruning.

While you’re out there whack back the ornamental grasses, also.  The new blades haven’t emerged yet and the plants are looking a bit tired anyway.

Got some overgrown shrubs that you’ve been meaning to (or reluctant to) prune heavily? Go for it now.  I understand that if you’ve never done it before it can be a bit intimidating. Trust me. The plant will almost always not only survive, but also thrive. I am aware of the never-more-than-a-third rule, but sometimes that is not enough. If it needs to go back to 12 to 18 inches, go for it. Chances are you and the plant will be glad you did.

Spraying

The orchard needs attention. Peaches and nectarines should be sprayed with a fungicide to prevent leaf curl. Spraying a dormant oil on the fruit trees will help control several insects later in the year.

Other fun stuff to do outside in February
Perennials can be divided if the soil ever gets dry enough.

Many landscape plants can be propagated via hardwood cuttings this time of the year. Some of the plants in the category are crape myrtle (Lagerstroemia species), flowering quince (Chaenomoles species), junipers (Juniperus species), spiraea (Spiraea species) and weigelia (Weigelia species).

Bluebirds will be most appreciative of a through house cleaning before the Spring nesting season. Remove all the old nesting materials and let them start afresh. It’s like clean linens for them.

Oh, yeah. Lest we forget … order flowers or other living things from the plant kingdom for your significant other. Just for the record, guys like flowers and plants, too. Happy Valentine’s Day!

Think positive thoughts about an early Spring and no late freezes.

Additional Reading from NC State Extension

Carolina Lawns: A guide to maintaining quality turf in the landscape
https://content.ces.ncsu.edu/carolina-lawns

Planting calendar for annual vegetables
https://content.ces.ncsu.edu/central-north-carolina-planting-calendar-for-annual-vegetables-fruits-and-herbs

Pruning trees and shrubs
https://content.ces.ncsu.edu/pruning-trees-and-shrubs

Plant propagation by stem cuttings
https://content.ces.ncsu.edu/plant-propagation-by-stem-cuttings-instructions-for-the-home-gardener