- Fall needle drop: A natural phenomenon in conifers
- Help a Newly Planted Evergreen Turning Yellow, Brown or Dying
- Why is my newly planted evergreen turning yellow or brown?
- Why Your Evergreen Needles Turn Yellow
- Not All Conifers are Evergreen
- Distribution of Coniferous Trees
- Characteristics of Coniferous trees
- Resin Ducts
- Uses of Conifers
- Simple Keys for Identifying Conifers: The Pine Family
Fall needle drop: A natural phenomenon in conifers
Every fall, people look forward to Mother Nature sharing her palette of reds, yellows, purples, browns, oranges and golds as deciduous tree leaves change color and drop in preparation for winter. We understand and expect the leaves on our maple, oak and elm trees to turn color and fall off. What many people are unaware of though is that most conifers also drop their needles at this time. Fall needle drop in conifers is no different than leaf drop in deciduous trees. The change in color and drop are a physiological response to the shorter days and cooler nights as trees prepare for winter.
Evergreen conifers such as pines, spruce, fir and arborvitae shed their oldest needles each year starting in late August and continuing into October. Their oldest, interior needles turn yellow while needles at the tips of the branches stay green. This yellowing and dropping of the interior needles occurs uniformly from the top to the bottom of the tree. When and how dramatic this event is varies with tree species, summer weather conditions and individual tree health.
Normal fall needle yellowing on Eastern white pine.
Photo credit: Steven Katovich, Bugwood.com.
Tamarack, larch and bald cypress are less familiar trees found throughout Michigan. While these trees are also conifers, they differ from the pine, spruce and fir in that they lose all their needles each fall.
This, too, is a natural phenomenon, but causes alarm to people unfamiliar with these deciduous conifers. Like other deciduous trees such as maples and oaks, these trees will grow all new foliage next spring.
Normal fall needle coloration on Larch tree prior to
shedding all its needles. Photo credit: Rebecca Finneran, MSUE.
While many people fear their conifer trees are dying when they notice yellowing and dropping needles in the fall, rest assured this is normal and tree health is not impacted. Bear in mind though that needle loss at other times of the year, or at the tips of the branches, is not normal for these species and may be due to an insect or fungal pest or the result of severe environmental stress.
- Gardening in Michigan
Help a Newly Planted Evergreen Turning Yellow, Brown or Dying
When you planted your new evergreen, you likely imagined it brightening up your snow-covered landscape. While most of your other plants slept, your evergreen would give you that burst of color you so desperately need in colder months!
So, why has your tree already traded in its signature color for dead-looking yellow or brown needles?! That’s not what you signed up for!
Keep reading to learn what’s going on with your evergreen and how to fix it.
Why is my newly planted evergreen turning yellow or brown?
Newly planted trees have a lot to deal with as they adjust to a new home. Even when we give them the best care after planting, they can still get stressed out.
That stress is known as transplant shock—it’s when plant roots struggle to adjust after changing their environment. Transplant shock can cause many problems, and yellowing or browning foliage is one of the most common and easy to spot!
Are there other reasons why a newly planted evergreen turns brown?
Transplant shock can make an entire evergreen shift from green to yellow or even brown. But, if you’ve only noticed small parts of your evergreen changing color, that may be normal.
Sometimes, inner evergreen branches turn brown while the outer limbs remain green. This is a normal, healthy part of the growth process. No need to worry if that’s the case!
Is my newly planted evergreen dying if it’s brown or yellow?
Trees suffering from transplant shock are still alive but need a helping hand to regain their health and beauty.
Here are a few ways to help your newly planted evergreen get its groove (and green) back!
As usual, growing a healthy plant is all about having a plant health care plan.
- Even if you water the lawn already, your tree needs its own drink of water! Give your tree about 1-inch of water every week (rainfall counts!) for the first year or two after planting.
- For now, only cut branches off your evergreen if they’re dead or damaged.
- Mulch the tree to help lock in soil moisture. The mulch should be about two inches deep and kept about five inches away from the trunk.
Learn the best way to water your newly planted evergreen tree.
Joseph OBrien, USDA Forest Service, Bugwood.org
Why Your Evergreen Needles Turn Yellow
These types of trees are commonly termed evergreens because their needles stay green year round. Well, at least most of the needles stay green. The average lifespan of evergreen needles is three years. In the fall of their third year, the oldest needles turn yellow and drop from the tree, leaving only the one and two year old needles on the outside of the branch. New needles form in the spring, at the tips of limbs, so again there is three years of needle growth on the tree. So if your evergreen has been healthy all season and then suddenly, in September or October, some of the needles turn yellow, don’t be alarmed, it’s natural – except in seasons of extended drought, where yellow needles can indicate tree health issues. Such is the case in years like this year where we have experienced a season with excessive drought stress. This will lead to more than the average amount of needle drop, and in some cases, defoliation.
If you are concerned about your evergreens, please call us at 877-308-8733 or request a free consultation with an Arborist, as they are trained to identify drought stress and differentiate it from natural third year needle drop.
Not All Conifers are Evergreen
Bald cypress knees (Taxodium distichum ‘Pendens’ 806-52*A). Photo by Kyle Port
If the needles are dropping off of your cut Christmas tree–most likely a fir (Abies) or pine (Pinus)–you know it’s time for it to go to the compost pile. Likewise, if a fir, pine, or other evergreen conifer (spruce , juniper , yew , arborvitae , etc.) growing in your yard dropped all of its foliage it would be a sure sign that something was drastically wrong with the plant. Conifers are supposed to keep their leaves all year, right?
Well, not necessarily. While it’s true that the majority of conifers are evergreen (they retain foliage for a full year or more), the word “conifer” is not synonymous with “evergreen.” There is a small group of conifers that grow and drop a new set of leaves every year, just like maples, birches, or other deciduous trees. There are five genera of these deciduous conifers, four of which grow in the Arboretum.
The larches (Larix) are the largest group of deciduous conifers with 11 species widely distributed in northern regions of North America and Eurasia. Tamarack, aka eastern or American larch (L. laricina), is one of three North American species; it has a wide range in northern tier states from Maine to Minnesota as well as much of Canada and Alaska. Taxodium is another North American genera of deciduous conifers, the most common species being bald cypress (T. distichum), noted for its iconic buttressed trunk and knees .
Dawn redwood, Metasequoia glyptostroboides, in the fall.
The other three deciduous conifer genera are all native to China (and Vietnam in one case), and, curiously, all are monotypic, meaning there is only one species within each genus. Golden larch (Pseudolarix amabilis) is a particularly handsome tree, its common name coming from the vibrant golden yellow its needles turn in autumn before dropping. The grove of golden larch (accessions 3656, 16779, 10764, and 187-94*A) along Bussey Brook at the southwest end of the Conifer Collection is a must-see at the Arboretum. And then there’s dawn redwood (Metasequoia glyptostroboides), a signature tree at the Arboretum (it’s featured on our logo and there’s a magnificent specimen 524-48*AA across from the Visitor Center). Read the whole story of the Arboretum’s involvement in the discovery and distribution of dawn redwood here .
The remaining deciduous conifer is not hardy at the Arboretum. Water pine, or Chinese swamp cypress (Glyptostrobus pensilis), is native to limited areas in southeast China and Vietnam; it is hardy only to USDA Zone 8 (average annual minimum temperature 10 to 20 degrees F ).
For a thorough overview of the gymnosperms–the plant group that includes conifers, ginkgos, and the fascinating Welwitschia, among others–see this Arnoldia article .
An evergreen plant is one whose leaves remain green for the entire year. This is the case even in instances where such a plant retains its leaves only in warm seasons as opposed to deciduous plants which shed all their leaves in dry weather or during winter. Evergreen plants are comprised of both shrubs and trees, chief among them being conifers. Conifers are plants which bear cones; they are woody plants and the majority of which are trees in addition to a small number of shrubs. They are evergreens with over 600 different species in existence all around the world. Conifers comprise some of the tallest and oldest tree species some growing up to 300 feet in height like the Coast redwood. The Bristlecone pine can live for a staggering 5,000 years.
Distribution of Coniferous Trees
With the numerous species, conifers are distributed in different places around the world, but they are mostly found in the Northern Hemisphere extending all the way to the Arctic Circle. They are also in both Central and Southern America, a few varieties in Africa as well as vast distributions in Asia and Europe. Some of the conifers which were introduced to New Zealand have become invasive and they include radiata pine, lodgepole pine, European larch, and Douglas dir. In South Africa species such as patula pine, maritime pine, and radiata pine have been named as invasive species.
Characteristics of Coniferous trees
Coniferous trees have several characteristics chief among these being their leaves which are why they are referred to as evergreens since they retain their foliage all year round by shedding and growing new ones simultaneously. Leaves of some coniferous plants are needle-shaped like the pine, spruce, and fir while others such as cypress have scale-like leaves, these do not form single leaves but entire branches of more than one year.
Conifers bear cones that are seeds and they are dispersed both by wind and animals. The seed cones have bracts, which bear semblance to actual seeds. They are partly hidden in some species like hemlock, or barely visible in firs while they are seen to be elongated and very prominent in the Douglas fir. When matured these seeds become large and woody.
Another trait in coniferous trees is the sticky secretion that is found on the bark of the tree. Resin ducts are the tubes that house the cells which secrete this pitch to the surface of the tree. It is used by the tree as a healing agent and close up wounds inflicted during the process of shedding cones, leaves, and even bark. On the surface, the resin is sometimes harvested for use in extraction of oils and other commercial use.
Uses of Conifers
Conifers are exploited for different reasons. Some of the uses include the production of paper and lumbering for purposes of construction. The conifers are robust and long-lasting and are therefore a favorite in making furniture. In addition to these, they have also been used in making anti-cancer medicine. Due to their several uses conifers have come under threat as a result of human activities of exploitation coupled with degradation of forest areas, which in effect have put about 34% of these species at the brink of extinction.
Simple Keys for Identifying Conifers: The Pine Family
Have you ever given much consideration to the various pine trees around you? My children and I have been slowly identifying the deciduous trees in our neighborhood and can now identify a few during the winter by the buds that develop in late summer. But it wasn’t until recently that we set on a quest to learn more about the many conifers we see every day. We quickly learned that what we generally call a pine may not be just a pine. If you would like to investigate the conifers of the pine family with your child, we have some simple keys that will help you distinguish them.
What exactly is a conifer?
Conifer stems from Latin and means “cone bearer”. There are seven different families of conifers, all of which bear cones. With a some exceptions, most conifer trees are evergreens that maintain their color and leaves throughout the year. They are easily identified by their needle-like or scaly leaves.
For simplicity, let’s focus specifically on evergreen trees of the pine family…
Who’s in the pine family (Pinaceae)?
This family of conifers include pines, spruces, firs, hemlocks, larches (these are not evergreens), and true cedars. Members of the pine family have needles as opposed to scaly leaves. Spruce, fir, and hemlock needles grow singularly on the branch. The needles of pine trees grow in bundles of 2, 3, or 5. True cedars have clusters of 15 or more needles and, although some species have been naturalized in North America, they are native to the Middle and Far East.
How to tell them apart
Remember that the needles of pines grow in clusters of 2 or more.
To distinguish between spruces and firs, all you have to do is “shake hands” with the tree. Spruces can be stand-offish because their needles are pointed and sharp. They are also usually square in cross-section, making it easy to roll between your fingers. Fir trees are much friendlier. Their needles are softer and flat, which cannot be rolled between your fingers. You can give this mnemonic a try to help your child remember: spruces are stiff and sharp, firs are flexible and friendly.
You can find more keys to help you identify these conifers on our flash card download. Print them on card stock or laminate them to bring them with you on your next walk or hike and see how many of the trees can you identify.
You may also find these resources helpful:
- Trees, Leaves & Bark by Diane Burns
- The Tree Book for Kids and Their Grown-Ups by Gina Ingoglia
- Where Would I Be in an Evergreen Tree by Jennifer Blomgren
- National Wildlife Federation Field Guide to Trees of North America
- What Tree is That? Arbor Day Foundation Online Edition
- Trees With Needles: Online Tree Leaf Key
flash card photo sources- spruce cone, eastern white pine cone, fir cones