Tree Stress

This spring we have several trees showing signs of stress that are not particularly attractive.  Since last fall, something has happened to them.  They leafed out late and/or they have some dead branches throughout the tree.  More than likely, it is a result of the historic cold temperatures this winter.  But it made me wonder about some other reasons these trees may be stressed this spring. 

Why trees?

Trees in Kansas are a luxury and one of your property’s greatest assets. To sit under a mature tree on a warm afternoon, enjoy the blue skies and sip your favorite cool drink is a special experience.

Trees need to withstand the rigors of the climate. Trees block harsh winter winds, give you privacy, delineate boundaries, offer great fall color, attract birds and other wildlife that enhance your enjoyment or your landscape, and increase its resale value. Trees are important for all of these reasons and more, but they are not invincible. At any moment, signs of stress can emerge, so we need to understand and make every effort to alleviate problems that may arise. 

Open-grown burr oaks are wider than they are tall (Photo by Lamar Roth)

Tree Stress Symptoms

Stressed trees are easy to pick out in the landscape. Symptoms will manifest in a number of ways including flaking bark, secretions, distorted or missing growth, insects, foliage issues, dead branches and lack of vigor. 

These symptoms are visual clues to internal, external or environmental stressors. Left untreated, these stressors could ultimately kill your tree. Stressed trees are beacons to insects because they are weaker and vulnerable to attack.  Compounding factors over a number of years from the same stressors or multiple stressors lead to tree fatality. Here are some common causes of stress in trees. 

Poor Tree Watering Techniques  

It is true that trees need water to survive, but they need just the right amount of water.  Too much or too little can cause a tree to be under stress. These problems can be compounded when planted in our clay soils. Defoliation, yellowing of the leaves and branch die back are all symptoms to avoid. Most trees, if properly situated, can withstand seasons of drought without much extra inputs. 

Monitor trees during stressful times such as drought to make sure they don’t need a deep soaking. Keep in mind that waterlogged soils are more problematic than drier soils because proper air exchange by the roots in hindered by extremely wet conditions. Sometimes we see a tree under stress from drought and do more damage by giving it too much water. Give it a deep soaking, but let it dry out between watering.   

Install the tree properly 

One of the first lessons I learned as a novice horticulturist is how to plant a tree. “How hard can it be?”, you may say.  Just dig a hole, put it into the ground, water it for a while and watch it grow. More trees are killed by improper installation than you might realize. Choosing the right tree for the soil conditions, along with understanding mature size, will go a long way to helping that tree survive and thrive. 

In our clay soils, I plant the root flair a few inches higher than the soil line in a hole that is at least twice the size of the root ball. I make a small basin around the tree that makes it easier to water and then lightly mulch the basin. It is important to keep mulch away from the trunk of the tree. I stake the tree for the first year and remember to remove the wires that will eventually girdle the tree if forgotten.

For some additional tips on how to properly plant trees, check out my blog post “Steps to Planting a Tree”.

Beware Lawn mowers and Weed eaters

Anything you can do to keep mowers and weed eaters away from the trunk of trees is vitally important. I have seen too many tree trunks damaged by mowers bumping them and people string trimming around the base of the tree, trying to cut down every sprig of grass. A small two to three foot mulch ring provides just the right buffer between the trunk and lawn.  I have seen a string trimmer completely girdle the soft bark of a maple tree and kill it in a couple weeks. If you have invested in a tree, protect it from these tree killers.   

Mulch Around Trees Properly

The advantages of mulch around trees are obvious. It is one of the easiest things to do and it improves the aesthetics of the landscape. However, too much mulch, mulch touching the trunk, or mulch volcanos around your trees could cause major tree stress. These stressors are totally avoidable with one to two inches of mulch around the trunk, but not touching the trunk. It is important to keep the mulch several inches away from the trunk. Too much mulch will cake up and seal off the soil, impeding proper air exchange by the roots.    

Too much mulch piled up at the base of the tree can lead to fungus, rot, low oxygen levels and tree death.
This is an example of a mulch volcano. Be sure to pull mulch away from trunk of tree and spread out.

Improper Tree Pruning

Pruning your trees as they mature is a necessary function. I generally prune our deciduous trees during the winter when they are dormant, making sure not to remove more than 1/3 of the growth at a time. Proper timing will allow the tree to begin to heal without opening up the tree to potential diseases and pests. Evergreen trees can be pruned any time but I avoid the hottest part of the year.   

Construction Injuries to Trees 

Trees often suffer during and after construction projects. Compacted soils and branch or trunk damage can stunt the growth for several years after the project has been completed.  It often takes years for compact soils to improve.  I killed several nice maple trees after our Visitor Center was constructed because the soil was too compacted.  The soil would not drain and they were essentially planted into an undraining bowl.  The roots were completely surrounded by water and they drowned and stunk when I pulled the dead trees out.  Remember to protect/ fence off any trees you want to save during a construction project. 

Environmental Injuries

There are so many nice trees and shrubs from which to choose. We often push the hardiness zones to grow trees that are borderline hardy in our area. As I mentioned earlier, we have a sawtooth oak and gingko that suffered damage from the extreme cold earlier this year. The are coming out of it, but they will look tough for a few years. These trees are not native and remind me to choose native plants first. It also reminds me to be aware of the hardiness of plants we install. Match plants up to your site, including sun, soil, exposure, hardiness, mature size, and moisture.

Sawtooth Oak winter damage

Trees are resilient, but we can help them by considering their needs. A little homework before planting can alleviate problems through the years. Trees are alive and ultimately affected by so many factors, some of which are out of our control. Who know what the next pest will be? Who knows when the next drought will occur? All we can do is try to create/match an environment conducive to growth.

Plant Profile: Southwest White Pine

When one thinks of classic and elegant conifers, Eastern white pine often comes to mind.  Unfortunately in the Great Plains, summer heat, wind and drought restrict growing Eastern white pine to only well protected sites.  We have a stand of Eastern white pines strategically planted with protection from these adverse conditions.  Even these few original Eastern white pines planted in the early 1980’s are slowly expiring because of environmental challenges. 

Fortunately, there is an alternative.  The Southwest white pine, Pinus strobiformis, is a tough, drought- and heat-tolerant conifer. Its native range extends from Texas to Arizona and south to Mexico.  They inhabit dry, rocky slopes in mountainous areas. 

Southwest white pine planted in 2000

Habit

Somewhat shorter and broader than its eastern cousin, the Southwest white pine reaches 30-60 feet in height at maturity, with a broad, rounded crown.  Needles are five per bundle (fascicle), 1.5 to 3.5 inches in length with a dark green to blue-green color.  The top and bottom of the needles have somewhat distinct white stomatal lines.  Though not as long and soft as the needles of the Eastern white pine, the needles are very soft textured and pliant.  The long cylindrical cones mature in two years and produce a brown oval seed that is edible.

This image has an empty alt attribute; its file name is IMG_2207-768x1024.jpg

Culture 

Adaptable to our high pH soils, Southwest white pine prefers well-drained soil in full sun.  It is a moderate to fast grower. Young specimens in the Arboretum have grown 10-12 inches per year since they were planted in the mid-1990s.

Also consider a Southwest white pine as an alternative to Austrian pine, which has suffered from Sphaeropsis tip blight in the last decade.  It can be used as a large specimen or in a screen or windbreak planting. Its hardiness, drought resistance, and fast growth are definite attributes to consider in our challenging climate. 

Alternatives

Other evergreen and conifers we use here at the Arboretum: Arizona Cypress, ‘Taylor Juniper’, ‘Canaertii’ Juniper, Black Hills Spruce, Pinyon Pine and Vanderwolf’s Pyramid Limber Pine.  There are no guarantees on any of these.  They may develop blights, or other diseases in time.  Certainly they are all attractive to bag worms. 

The bottom line is that growing evergreens in Kansas will always be a challenge.  These are the best options for landscapers. Take a look at our 2020 Native Plant Guide for Spring FloraKansas Native Plant Festival for other landscape options.

Arizona Cypress

The Best Trees for Fall Color

‘The best time to plant a tree was 20 years ago. The next best time is now.’

– Chinese Proverb

 

For many reasons, fall is my favorite time of the year.  I love the cooler weather and changing landscapes.  This signals the end of another growing season, but there are still a few highlights to come. The beauty of the fall wildflowers like asters and goldenrods makes them stand out in a sea of grass.  The native grasses are at their peak with attractive seed heads and brilliant fall color.  It is also a time when trees begin to change, developing shades of red, orange, yellow, and tan.  I know winter is coming, but the crescendo of our gardens is fun to watch.

Native Blackhaw Viburnum (Viburnum prunifolium)

How do trees develop fall color?

Fall color in trees is a result of a complex process of removing the green pigment, chlorophyll, from the leaves, which allows the other pigments to be seen.  For instance, carotene and xanthophyll (carotenoids) are yellow pigments that are produced all year long with chlorophyll.  With the shorter days and cooler fall temperatures, chlorophyll production is slowed and the green color slowly disappears revealing the yellow pigments that have been there all year long.  Green ash and ginkgo are good examples of trees with nice yellow fall color.

Other trees produce red and purple pigments called anthocyanins, which tend to cover the yellow pigments present in leaves during the fall.  As the fall season progresses, the increased sugar content in these leaves works to intensify these reddish-purple leaves.  American ash, shingle oak and shumard oak are nice trees with red fall color.

In trees with a combination of carotenoid and anthocyanin pigments, an orange fall color develops.  Sugar maples, smoke trees, and sweet gum trees are wonderful examples with orange fall colors.

Some of our trees have no vibrant fall color, but rather the leaves turn to tans and browns. This is caused by tannins in the leaves, which accumulate as the chlorophyll is removed from the leaves.

Fall color can be a little different every year.  Plant genetics, and environmental conditions make subtle changes from year to year fun to watch.  Each year, there is a unique beauty in the landscape that should be savored, enjoyed and not taken for granted.

White oak

My Favorite Trees for Fall Color

Shumard Red Oak (Quercus shumardii)

This oak tree will reach a height of 40-60 ft. with a nice rounded-pyramidal habit.  It is a stately tree that produces a wonderful range of colors from deep red and maroon to dark oranges.  Fall color can be quite variable from year to year depending on environmental conditions.  Other oaks worth trying: shingle oak, white oak and black oak.

Sugar Maple (Acer saccharum)

Sugar Maples and many other maples are the quintessential tree for fall color. In Kansas, sugar maples are relatively slow growing but worth the wait as a mature tree can put on quite a fall display.  They reach an ultimate height of 40-50 feet tall and equal spread.  The bright red, orange and yellow leaves appear in October and last for many weeks.  Try the cultivars, ‘John Pair’, ‘Autumn Splendor’, ‘Table Rock’, ‘Flashfire’, ‘Oregon Trail’ or ‘Legacy’ for the most consistent fall color each year.

Table Rock Sugar Maple

Bald Cypress

This is not usually recognized as a tree with exceptional fall color, but when the fine leaves turn reddish-brown in the fall, it is striking.  We have planted Our specimens near the pond where the “knees” can develop. The pyramidal habit reaching 50-60 feet tall make it a majestic tree for certain situations. It is certainly worth a try.

Bald Cypress fall color

Others worth noting:

  • Viburnum rufidulum
  • Viburnum prunifolium
  • Cotinus ‘Grace’
  • Betula tremuloides ‘Prairie Gold’
  • Sassafras
  • Ginkgo ‘Autumn Gold’
  • Carya cordiformis
  • persimmon

We are already seeing signs of fall here at the Arboretum.  Fall color starts in September and ends in November with peak coloration sometime in October.  Cool night temperatures above freezing, calm winds, and sunny days will make the colors more intense.  So, even though it’s not New England, let’s enjoy the beauty of fall.

Sugar Maple






Trees For the Kansas Home

At last year’s fall plant sale I convinced my father to plant some oak trees around his house where older shade trees are nearing the end of their lives. I told him to think ahead ten years: when the sweetgum (Liquidambar styraciflua) in the front yard finally dies, won’t he wish that he had a head start on growing the next shade tree nearby? And wouldn’t it be nice to start a row of trees near his workshop to block the hot west sun? Of course! He ended up choosing a few Shumard oaks (Quercus shumardii) which have done well for him and are off to a great start.

These trees were an investment in the future of his property ownership – well placed trees can save you money on heating and cooling your home and offer protection to your roof and siding from the sun’s damaging rays. Are there parts of your yard that need a shade tree? Or perhaps you have a tree that will need replacing in the near future?

Do your research and find the perfect tree for your needs, practical and aesthetic. Following are some of my favorites from the upcoming sale, but a full list is available here.

Fruiters

If you want to add a fruiting tree to your landscape, consider a Kansas native. PawPaw (Asimina triloba) and Persimmons (Diospyros virginiana) are both delicious and underused native fruits. Both are small to medium sized trees when mature (20 to 40 feet tall) and grow well in moist to medium-dry environments.

Persimmon (left) and PawPaw (right) both produce delicious fruit.

Persimmon (left) and PawPaw (right) both produce delicious fruit.

Understory

Sassafras albidium is the host plant for the spicebush swallowtail (Papilio troilus)

Sassafras albidium is the host plant for the
spicebush swallowtail (Papilio troilus)

If you already have some large shade trees and want to add canopy layers, consider an under story tree that thrives in the dappled sunlight and protection of larger trees nearby.  Sassafras trees (Sassafras albidium) have unique foliage, showy spring flowers and all parts of the plant have a pleasant smell. Eastern Wahoo (Euonymous atropurpureus) is known for it’s intense fall color and often grows in a shrubby form.

Flowering

There are lots of showy flowering trees to choose from, but we carry a few particularly unique options. Hop hornbeam (Ostrya virginiana) has cream colored shrimp shaped flowers, seen below. Yellowwood (Cladrastis kentukea) trees have pendulous white blooms and bright golden fall color.

Blooms of hop hornbeam and yellowwood trees.

Blooms of hop hornbeam and yellowwood trees.

Shade

Big sturdy shade trees are a good choice for a homeowner looking to reduce their electricity bills and protect their home from the elements. Black oak (Quercus velutina) and American Chestnut (Castenea dentata) both grow upwards of 60 feet tall and both produce nuts that provide winter food for wildlife.

Planting a tree is a satisfying task — it is an investment in the years to come, the hope of growth and newness. A mature tree can even raise the market value of your home! Tree coupons for the fall plant sale (September  9 – 11) will be available soon on our website. Hope to see you at our upcoming sale, carting away a tree of your own.

Photos from wikimedia comons, attributed to: Asit K. Ghosh Thaumaturgist (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons
Hophornbeam by Eric Hunt (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
Cladrastus bloom Elektryczne jabłko (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 4.0-3.0-2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/4.0-3.0-2.5-2.0-1.0)], via Wikimedia Commons