Christmas trees – The Garden Professors™

The Walking Dead: Christmas tree edition

Zombies are big deal these days. Seems like you can hardly turn on the TV these days without seeing someone (or someTHING) coming back from the dead. Turns out Christmas trees are no exception. Every so often during the Holidays I will get a call or an e-mail that starts off, “My Christmas tree is starting to GROW!” And indeed they are. Under certain circumstances, conifers that are cut and brought indoors can break bud and begin to grow; sometimes putting on considerable new growth.

It's alive! Concolor fir Chrsitmas tree pushing new growth. Photo: Doug Thalman — It’s alive! Concolor fir Chrsitmas tree pushing new growth. Photo: Doug Thalman

So what gives? Like the proverbial chicken running around with its head cut off, Christmas trees are dead they just don’t know it yet. After they are cut, conifers can continue physiological functions – photosynthesis, transpiration, respiration – for weeks. In some cases they can break bud and begin to grow like it’s springtime when a homeowner brings them indoors. There are a couple of key factors that come into play. First, the tree must be exposed to enough cold weather to meet its chilling requirement. This varies among species, but most conifers need to accumulate at least 6 weeks of chilling below 40 deg. F to overcome dormancy. So early cold weather where the tree is grown and harvested is step one. Second, the “Zombie tree syndrome” is most likely to occur in species that are adapted to high elevations or northern latitudes. The usual suspects are concolor fir (Abies concolor) and corkbark fir (Abies lasiocarpa var. arizonica). These trees have evolved in areas with a short growing season, so there is a selective advantage to breaking bud rapidly when weather warms in the spring – or if brought into a toasty 70 degree living room.

Walking dead - new growth on concolor fir Christmas tree. Photo: Doug Thalman — Walking dead – new growth on concolor fir Christmas tree. Photo: Doug Thalman

So what do you do if your tree turns into a Zombie and comes back from the dead? Don’t panic. It’s a natural phenomenon; just be sure to check and refill the water in the stand regularly so the new growth doesn’t desiccate. And lock your bedroom door at night – just in case…

If trees have met their chilling requirement the they can begin to growth when brought indoors. Photo: Doug Thalman

Silence of the lamb chops

One of my ‘other duties as assigned’ this time of year involves serving as The Christmas tree Guy and responding to various media inquiries about Christmas trees. Last week I posted a link to a media story about Christmas trees on the Garden Professor Facebook page. That post drew a response from Kyle Fletcher Baker who derided cut Christmas trees as “murder of the innocent.” My initial reaction was, “Jeez, Kyle we’re talking about fir trees here not lamb chops or veal.” But Kyle’s post serves as a reminder that there are many people that object to cutting trees for Christmas decoration – no word on how these folks feel about cut flower arrangements but that’s another story. In some cases this objection stems from the belief that Christmas trees are cut from native stands of trees. In fact, virtually all Christmas trees sold at tree lots are grown on tree farms for that expressed purpose.

There is also a sizable portion of the population that believe artificial trees are more environmentally responsible than using a live tree. My personal opinion is this is a fairly small factor in most people’s tree buying decisions but the question persists and seems to get a lot of media play. The American Christmas Tree Association (a trade group that represents artificial tree retailers NOT tree growers) commissioned a life cycle analysis (LCA), which estimated cradle-to-grave carbon footprints for real and fake trees. The bottom-line of the study is that the impact of both is negligible. The tipping point is how far you drive to get a real tree each year and how long you keep your artificial tree. If you get your real tree close to home or combine getting your real tree with other trips, the carbon footprint of the real tree comes out better.

But if the thought of cutting a real tree is still more than your conscience can bear, there is a third option: a living Christmas tree. Many nurseries and Christmas tree farms offer container-grown or balled-and-burlapped trees that can be planted outdoors after the holidays. There are even companies springing up on the west that specialize in live Christmas tree rentals. These companies bring a tree into your house and then pick it back up after the holiday. Some will offer a certificate that the tree will be planted in a park or national forest after its display.

A Tree Story

Given my line of work, it’s probably no surprise I’m a sap for tree stories (no pun intended). Last week I was in Nova Scotia for the biennial International Christmas Tree Research and Extension conference. The conference and associated tours provided an opportunity to learn about Christmas tree production in Nova Scotia, one of the leading Christmas tree producing regions of North America. During the conference I also learned about the annual tradition of Nova Scotia’s Tree for Boston.

Each year Nova Scotia, through its Department of Natural Resources, presents a 40’-50’ Christmas tree (balsam fir, white spruce or red spruce) to the city of Boston. The gesture is an annual reminder of Nova Scotia’s gratitude for Boston’s and Massachusetts’ immediate aid and generosity in response to the Great Halifax Explosion of 1917. For those of you, like me, that were not familiar with the story, the Great Halifax Explosion occurred in Halifax Harbor on the morning of December 6, 1917. The French Freighter Mont Blanc, packed with explosives bound for the Allies’ war efforts, collided with another ship and caught fire. The explosion that followed, reported to be the largest man-made explosion of the pre-nuclear era, leveled a large portion of Halifax and neighboring Dartmouth, killing nearly 2,000 people and injuring 9,000 more. Within hours of the massive explosion, the governor of Massachusetts sent two trainloads of relief supplies to the devastated city. As a token of their appreciation, the citizens of Halifax provided Boston with a Christmas tree for Christmas 1917.

The tradition of providing a Tree for Boston was revived 1971 and has become an annual event ever since. While the cynical may deride this as a crass and commercial promotion for tourism and Christmas tree exports, the gratitude and affection of Nova Scotians for Boston seems heartfelt nearly a century after the disaster. And, if nothing else, Nova Scotia’s Tree for Boston serves as a history lesson, at least for those of us in the U.S., on this over-looked chapter of World War I.

Must we continue to bring in exotics?

A couple weeks back I posted about a collaborative research project that I am involved with to identify seed sources of two Mediterranean fir species (Turkish fir and Trojan fir) for use as Christmas trees in various locations around the country. The post prompted a question from Monta Zengerle who asked, “Must we continue to bring in exotics to satisfy the nursery trade?” Since our intended purpose is Christmas trees and people move plants around the world for purposes other than nursery stock, I’ve broadened the question to “Must we continue to bring in exotics?” for this discussion.

Not all exotic species introductions are man caused. This dock washed ashore in Oregon following the Japanese tsunami carrying all kinds of critters with it.

The answer, of course, is “No.” As human beings the only things we absolutely have to do are eat, sleep, and breathe. But the reality is much of the food and fiber production around the world, as well as our amenity plantings, are based on exotics plants. Human agricultural history is largely the story of plant importation and subsequent breeding. As Thomas Jefferson famously observed, “The greatest service which can be rendered any country is to add a useful plant to its culture.” However, it is doubtful that Jefferson considered kudzu or purple loosetrife could be among those plants added to our culture. Today we have a different understanding and realize that along with the economic benefits of plant exploration and importation comes the possibility of unintended and serious ecological consequences. And we’ve realized this for some time. People that deal with plant introductions on a regular basis talk about ecological errors and economic errors. If we allow importation of a plant that later turns out to be ‘bad actor’, we’ve made an ecologically harmful decision; if we ban a useful plant that ultimately would have turned out to be non-invasive, we’ve suffered an economic loss. Fortunately, only a small percentage of exotic species become naturalized and only small percentage of naturalized species become invasive. The underlying challenge is we cannot predict with 100% certainty which plants will be invasive in a new environment and which won’t. Ecologists are working on it and we can certainly begin to judge the invasive potential of new introductions. In the meantime, we are left with the imperfect calculation of whether the potential economic upside outweighs any potential environmental risk.

‘Top-work’ on noble fir in Oregon to maintain a single terminal leader. Turkish fir typically require less top-work.

So let’s look at our current project as a case study. What’s the upside? Christmas tree growers in the U.S. produce roughly 20 million trees annually. That’s a potential economic impact of hundreds of millions of dollars and seasonal and full-time employment for workers on over 13,000 farms from North Carolina to Washington State. A major issue for growers in virtually all of the principle growing regions is phytophthora root rot. Previous work at Oregon State University indicates that Turkish fir is highly resistant to this pathogen. By identifying seed sources with phytophthora resistance and superior Christmas tree characteristics (tree form, needle color, post-harvest needle retention), we will enable growers to continue or expand production and give consumers an additional choice for their holiday tree.

Native noble fir (left) is highly susceptible to root rot. Turkish fir (right) is much more resistant.

What’s the down side? As I mentioned, predicting invasiveness is difficult. That said, firs have several characteristics that make them unlikely invaders. Most firs have a relatively long juvenility period (age before they produce seed) which means they have a long period between generations. Secondly, most fir species produce seed crops sporadically as opposed to producing heavy seed crops year after year. Ecologically, firs are pretty wim
py; growing best on moisture, well-drained sites and unlikely to aggressively colonize disturbed areas. Lastly, the best predictor of invasiveness is invasiveness – a plant that has become invasive in one location is a candidate to become a repeat offender in a similar environment. Among conifers, the greatest issues with invasives have been pines (genus Pinus), in the southern hemisphere. In fact, all of the documented cases of invasives in the pine family (Pinaceae) are Pinus species; none were Abies. Based on all this, the likelihood of Turkish fir or Trojan fir becoming ecological problems appears very small, while the potential to add a useful plant to our culture is clear.

Exotic giant sequoias at Hoyt arboretum, Portland, OR.

Richardson, D.M. and Rejmánek. 2004. Conifers as invasive aliens: a global survey and predictive framework. Diversity and Distributions 10:321-331.

You don’t have to be crazy to work here, but it helps

Recently I spent a week in Oregon working on a Christmas tree genetics project along with my colleagues Chal Landgren( Oregon State University), Gary Chastagner ( Washington State University), and John Frampton (North Carolina State University). The objective of the project is to identify superior seed sources of Turkish fir and Trojan fir for use as Christmas trees around the United States. We refer to the project as the Cooperative Fir Genetic Evaluation or CoFirGE – remember, the most critical step in any experiment is coming up with a catchy acronym. CoFirGE began with a trip by my colleagues to Turkey where they collected seed from 100 fir trees across a range of sites in Turkey

Turkish fir growing in western Oregon

Why are we interested in these species? Both Turkish and Trojan fir are closely related Nordmann fir, which is widely used as a Christmas tree in Europe. These species make wonderful Christmas trees due to their symmetry and needle color. In addition they may be resistant to diseases, particularly Phytophthora root rot, that plague Christmas tree growers from Washington State to North Carolina.

So, what was going on in Oregon? After the seed were collected in Turkey they were sent to Kintigh’s nursery near Eugene, Oregon, where the seed were sown to produce seedling plugs. The next step of the project will be to send the seedlings out to cooperators in five locations (Pacific Northwest, Michigan, North Carolina, Pennsylvania, and Connecticut). This is tree improvement on a grand scale. In each region there will be two test plantings and each planting will include 30 reps of 100 seed sources or 3,000 trees. Multiplied by 5 regions and 2 plantations that’s 30,000 trees total that we will collect data on for the next 8-9 years.

30,000 seedlings ready to be sorted and shipped

Each seedling is individually labeled with a bar code for identification

Sorting into to boxes to send to cooperators around the country

But step one is getting the seedlings from the nursery to the out-planting sites. That means lots of tagging, sorting, and bagging. With help from technicians and students from WSU, OSU and NCSU and staff from Kintigh’s we were able to get all the seedlings sorted and bagged by mid-day on Thursday and start them on their journey to their new homes. Next step: Planting…

Finding agreeable things not sought for

As a graduate student at the University of Georgia many years ago I took a course in research methods. One of the discussions that stuck in my mind all these years centered on the word ‘Serendipity’. The classic definition of the word is “the faculty or phenomenon of finding valuable or agreeable things not sought for.” As scientists we rely heavily on the scientific method as a systematic method of inquiry to make new discoveries. But we also need to need to keep our eyes and minds open to serendipitous discoveries along the way as well.

So what got me thinking about serendipity? A few weeks back I visited a Christmas tree grower in northern Michigan with Jill O’Donnell our state-wide Christmas tree educator. The grower called us in because he had some questions about some unusual trees in one of his Fraser fir plantations. And, not only were the trees unusual, they were gorgeous. The only question was; what were they? The plantation originated from seed the grower had collected himself from some older Fraser fir trees he kept as a seed orchard. He sent the seed to a large forest nursery in the Northwest, which grew the seedlings and sent them back to him. The grower wondered if seed of another species could have been introduced in the process. Possible, I told him, but not very likely. Nurseries that are serious about contract growing are meticulous in keeping seed lots separate – few things are worse in that business than sending the wrong seedlings. Plus, I’ve worked with many species of fir and this was one I didn’t recognize. The trees had many characteristics of Fraser fir but also had attributes of concolor fir; long bluish needles and a slight hint of citrus scent when the needles were crushed. Many fir species can hybridize and all I could think was these trees had to be hybrids. “Are there any mature concolor firs near the seed orchard?” I asked. The grower brightened, “Actually there’s a group of older concolors about a half mile up the hill from the Fraser fir orchard.” We jumped in his pick-up and visited the concolor firs. Many of the trees had cone stalks indicating they were reproductively mature and could produce pollen. Conifer pollen can travel for miles so it’s reasonable to expect that some of the concolor pollen could reach the Fraser firs, which were downhill and downwind based on the prevailing winds in the area.

Excellent tree form of the mysterious hybrids

So what’s next? There are several reasons to follow up on this serendipitous discovery and try to make some additional crosses. First, as evidenced by the photos, the trees look fantastic. Second, Fraser fir and concolor fir are each great trees but they also have some liabilities. A downside of concolor is that they break bud early and often suffer late frost damage – Fraser’s break bud late. Fraser fir need acidic, well drained soils – concolor fir can grower on a broader range of sites. It’s possible that the hybrids will have intermediate characteristics that would make them ‘the best of both worlds’.

Foliage close up

The only thing left is to decide what to call the hybrids. Nurseries like to combine common names. So, Craser fir? Froncolor?

Last minute advice about Christmas trees and other fun stuff

The next podcast is up and running for your listening pleasure. I’ve got an interview with Dr. Gary Chastagner, WSU’s Christmas tree expert. He’ll tell you about his latest research and share some tips for keeping your tree happy and your carpet needle-free.

Here are some photos from Gary’s “dungeon” where he’s been comparing needle retention with some new promising conifer species from other parts of the world:

In the dungeon with Gary Chastagner

What dungeon would be complete without a rack or two?

I know which one I’d choose…

If you are really hard core, here’s a link to some of Dr. Chastagner’s research. Just look for the Christmas tree heading and click on it.

What fir?

OK, it’s the middle of December so I get to indulge my passion for Christmas trees. One of the most interesting projects I’ve gotten to work on during my time at Michigan State is a study to look at alternative species of firs (Abies spp) for Christmas trees and well as for landscape conifers. Firs are fascinating trees that are distributed throughout temperate regions of the northern hemisphere. There are about 50 species, many of which are important for timber, landscaping or Christmas trees.

For those of you that put off your Christmas tree shopping until the end (or want to start thinking about next year’s tree) here are three trees to keep an eye out for.

Korean fir Abies koreana We have several growers in Michigan that are now growing Korean fir. It has relatively short needles that have a bottle-brush arrangement on the stem. The color is often described as dark green, but I’d say the needles tend more to a true green or Kelly green with a silvery underside.

Concolor fir also makes a great landscape conifer

Conolor fir Abies concolor I grew up in the Northwest so I always knew this tree as white fir until I moved to the Midwest. In any case, it’s a great tree. Long, soft-blue needles. Depending on the seed source they can be as blue as a blue spruce. The main draw-back here in Michigan is that concolor tend to break bud early, which makes them susceptible to frost damage in the spring. Their citrus-like scent is hard to beat.

Danish growers compete for the best Nordmann fir in the “Fight for the Golden star” at their annual tree fair.

Nordmann fir Abies nordmanniana Denmark is the leading producer of Christmas trees in Europe and Nordmann fir is their principle species. The Danes like Nordmann because of its deep, dark green color and natural form and symmetry. Europeans don’t like their Christmas trees sheared so they rely heavily on genetics and selection to find trees that naturally have good form. We’re starting to see more Nordmann in the US, both here in the Midwest and in the Northwest. Growers complain that the trees are slow-growing to start but I think some US consumers are looking for a more open, natural-looking tree and Nordmann can fill this niche.

And now for something completely different…

From this week’s e-mail file…

“Dear Dr. Cregg:

As I’ve done for many year, this year I harvested my “wild” Christmas tree from the Huron-Manistee National Forest. I cut the tree at ground level. Soon after I brought it home, it started sprouting new light green clumps of needles at the tips of many branches. Is the tree actually growing? It doesn’t seem possible that it’s still alive, but it seems to be thriving and I hate to toss the tree to the curb if it’s fighting for life. I am tempted to leave it in the tree stand to see what happens….”

Pat M.

Midland, MI

Dear Pat:
The tree is dead, it just doesn’t know it yet. Depending of the species, some Christmas trees will break bud and begin to grow once they are brought indoors. The tree is still alive in the sense that its needles are still carrying out photosynthesis and water is still moving up the trunk to the needles. But since the tree has no roots and no way to produce any new roots, it has no prospect for long-term survival. The phenomenon you’re observing is common in some spruces and other conifers adapted to cold regions. Before you cut the tree, the buds were exposed to enough cold to meet their chilling requirement to overcome dormancy – the only thing that keeps trees in wild from growing at this point are cold temperatures. Once you brought it indoors, the tree ‘thought’ is was spring and started to grow. If you or a family member want to do a little science project you could keep the cut end in water and see how long the tree lasts. Eventually, however, the conducting elements at the cut end will begin to plug with resins and the tree won’t be able to move enough water to meet its needs and will expire.

Regards,
Bert Cregg

O Tannenbaum!

Twas the blog before Christmas… My last chance to post about Christmas trees for another year. I’m always surprised when I troll around the web or do interviews how many myths about Christmas trees still abound. So in the spirit of the season, a little Christmas tree myth-busting.

“Good grief. I’ve killed it.”

Using a real tree hurts the environment
Here’s a real post from the e-how.com website:

“Its so not fair to cut down all those baby trees, use them for a few weeks and then toss them by the curb for garbage removal. Everytime, i pass by a house and i see those poor trees just shoved out like that it breaks my heart. they belong in the forest or backyard where they were meant to be, growing old and improving the air and atmosphere. i used to like real Christmas trees but not anymore.”

Yes, Virginia, there are still people out there that think Christmas trees are cut from forests. The U.S Forest Service and some state forestry departments do offer permits to cut Christmas trees but this is a tiny fraction of the trees used in the U.S. Virtually all Christmas trees sold at tree lots and stores are grown on Christmas tree farms for that purpose. For each tree cut, growers plant two or three more. Moreover, many communities have programs for re-cycling Christmas trees into mulch or compost.

Christmas trees are a fire hazard.
The key here is water. Fresh Christmas trees that are properly watered are not a fire hazard. Trees that are allowed to dry can be a fire hazard. These are the ones your local TV station uses for their annual dramatic Christmas tree fire video.

Fire retardant sprays make Christmas trees safer.
Research by Dr. Gary Chastagner, a colleague of Linda’s at WSU-Puyallup, has shown that some fire retardants can actually increase tree moisture loss. Maintaining tree moisture is the key to making trees safer and improving needle retention. Making sure the tree stand never dries out is much more important than a fire retardant spray.

Injecting water directly into the stem is the best way to maintain tree moisture content.
This is a case where a little knowledge can be a dangerous thing. Since water moves up the tree through the xylem elements in the stem, wouldn’t injecting water right into the stem be the best way to water? That’s the logic behind the Tree I.V. As the name implies, this device is like an I.V. drip for your tree. Drill some holes in the trunk, attach some tubes to a jug a water, and voilà, a self-watering tree! We can thank Gary Chastagner again for busting this myth. He and some colleagues found that displaying a tree in a regular tree-stand with water maintained higher tree moisture levels that the I.V. technique.

So, if arborists can use trunk injection to apply pesticides and fertilizers to trees, why wouldn’t the Tree I.V. work? Actually, the tree I.V. does work in the sense that the tree will take up water from the jug. The problem is that the tree may not take up enough to meet its total water need. In a normal stand, the entire stem cross section is exposed to water. With the tree I.V. only a portion of the stem will be translocating water. Plus, conifers contain resin ducts which clog injection ports. This is one of the reasons why arborist’s trunk injections don’t work as well as on conifers as they do on most hardwoods.

Bottom-line, keeping your Christmas tree hydrated is the key to retaining needles and keeping the tree safe. A good rule of thumb is that a stand should hold a quart of water for each inch of tree caliper at the base. For most trees this means a stand that will hold at least a gallon of water. Check water in the stand daily and never let the tree go dry.

Have a very merry Christmas!