Christmas Tree Notes
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Christmas Tree Notes |
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CTN - 017
Eric Hinesley, Horticulture
William T. Huxster, Extension Forestry
Craig R. McKinley, Extension Forestry
Updated October 30,1995
Fraser fir competes well with other trees in the national Christmas tree market. When healthy and fresh, it is a beautiful tree with dark green color, good fragrance, and outstanding needle retention. However, cut Christmas trees, including Fraser fir, can perish quickly if not handled properly. The purpose of the following information is to provide retailers with the latest update of experience and research so they can provide customers with fresh trees that will remain serviceable throughout the holiday season.
Needle retention is related to dormancy and cold hardiness. Hardening is mainly a response to short days and low temperatures in late fall. In general, Fraser fir grown in the mountains of North Carolina have held up well in all areas of the United States and Canada. Currently, it is not possible to determine the earliest date in the fall when trees can be cut and exhibit good postharvest keeping quality. Trees that are not adequately frost hardened do not hold their needles well, and dry much faster following harvest. Early in the fall, hardening can be reversed if cold periods are followed by several days of warm weather. Problems with shedding of green needles, especially in the lower crown, often arise when trees are cut during mild weather in November. Try to ensure that trees are cut and delivered as late in the season as possible. Also, split shipments should be considered.
Tree freshness is probably the most important criterion of consumer acceptability. Look for the following in a fresh tree: high moisture content; little or no loss of green needles, no evidence of mold on foliage; fresh, resinous smell; needles that break crisply when bent, and bark of current-year twigs should be smooth without wrinkles or furrows. Dry needles are more pliable and tend to bend rather than break. If the bark of small twigs has wrinkles and furrows, the tree is already too dry to rehydrate (take up water). These criteria apply to the merchandise from the time of receipt until it is sold.
An index of freshness in cut Christmas trees is the "critical moisture content", below which a tree will not fully rehydrate when the trunk is recut and stood upright in water. Twigs of freshly cut trees normally have a moisture content (MC) (dry weight basis) of approximately 110% to 120%. For example, a fresh twig with 110% MC might weigh 2.1 grams, with 1.1 grams being water. The critical MC of Fraser fir and balsam fir twigs is approximately 75%. At that point, the twig that originally weighed 2.1 grams
Eric Hinesley, Horticulture William T. Huxster, Extension Forestry
Use of trade names represents neither an endorsement by the North Carolina cooperative Extension Service nor criticism of similar products not named.
would weigh 1.75 grams. A Fraser fir with moisture content below 70% to 75% is already too dry. The most accurate way to determine MC is with a pressure bomb. Readings can be taken quickly, and one twig per tree is adequate. Checking 2 or 3 trees in a load will give a relatively accurate picture of moisture status for all the trees.
Heat and sunlight are the greatest enemies of cut Christmas trees. At temperatures above 70 degrees F, trees lying unbaled on retail lots can lose up to half their moisture reserve in 24 to 48 hours. Avoid piling baled trees on hot parking lots or against south-facing brick or concrete walls. Trunk splitting is caused by rapid drying and resulting wood shrinkage. Split trunks, although unsightly, have little effect on the ability of trees to rehydrate or endure in the postharvest environment. Shading eliminates "stringburn", in which needles adjacent to the string turn brown. Stringburn on a baled tree in direct sunlight can occur in less than 30 minutes, particularly at temperatures above 70 degrees F. It can also result when frozen trees or those covered with frost are suddenly exposed to sunlight.
The best storage condition is low temperature (33 degrees F to 50 degrees F), high humidity (approximately 90%), and no light (darkness). The lower the relative humidity (RH) and the higher the temperature, the faster trees will dry. Fraser fir stored in darkness at 50 degrees F and 90% RH reaches the critical moisture content in about 30 days, compared to 2 to 3 days at 77 degrees F and 25% RH. Drying at high temperature (77 degrees F) is considerably faster than at lower temperatures (50 degrees F), even if the drying stress is constant.
Conditions essential for maintaining freshness are also critical during transportation from farms to the retail lot. Preferred transport is refrigerated trucks, particularly in areas south of North Carolina, and for distances greater than 400 miles. When using dry, closed vans, don’t allow the vehicle to stand in the sun for extended periods because if quickly leads to overheating and spoilage. Avoid temperatures above 80 degrees F in closed storage because trees can turn brown. For long-term storage in refrigerated trucks, trees should be loaded and baffled to allow for air circulation on top, bottom and sides. Trees hauled long distances on open trucks should be smoke tarped on the front and covered with shade cloth on the top and sides to prevent windburn and damage from diesel smoke.
Handling trees carefully is critical in unloading trucks, placing in and out of storage, and delivering to the customer. Minimize or eliminate walking on baled trees because it breaks limbs and leaders, and crushes foliage. Be especially careful handling frozen trees, as they are very brittle.
Store trees upright in a shady, cool place, out of high traffic areas. If permanent shade is unavailable, use a tarp or shade cloth suspended above the trees and down the sides with at least 2-foot air space. This eliminates stringburn, severe drying from wind, and keeps temperatures cooler. In severe drying conditions, misting trees at night is beneficial. Don’t soak piles of baled trees because it can cause molding and defoliation. Mold develops quickly only when temperatures are warm or hot.
Displayed trees should be sold on a "first in, first out" basis. The approximate time required for trees to reach the critical moisture content should be determined, and prices discounted at the time to hasten movement. Simple coding on tree tags will enables retailers to know exactly how long each tree has been on display. When displayed trees are no longer fresh or meet the above criteria of freshness, they should be removed from sale and replaced with fresh trees from storage.
In warm marketing areas (temperatures above 50 degrees F), trees should be displayed under shade, protected from the wind, and standing in water. This allows trees to completely rehydrate, and improves freshness. However, trunks should be recut (1/2" disc) before trees are placed in containers. Keep containers filled. Research with Fraser fir indicates that a customer has at least 8 to 12 hours to return the tree to water without having to recut. If a customer has no saw, make a fresh cut before the tree leaves the lot. Customers should be reminded not to get the end of the trunk dirty or muddy. If the trunk is too large to insert into a ringed stand, it is OK to taper the end, provided the tapered part remains submerged in the stand. Otherwise, the wood pores seal and do not take up water. Wood just beneath the bark is most effective in moving water up the trunk.
Emphasize to customers the importance of using a large water capacity stand. Heavy density Fraser fir Christmas trees can use about 1 quart of water per day per inch of trunk diameter; 6' to 8' trees frequently consume 4 to 5 quarts/day. Stress the importance of not letting the stand go dry; such trees often do not rehydrate when water is added. Fresh trees are almost impossible to set afire.
People often ask if additives in the stand can prolong the life of displayed trees. Research has shown additives to be of no real benefit. This includes such things as aspirin, clorox, sugar and 7-Up, as well as assorted commercial products. Some materials actually increase needle drop, and many cause trees to consume more water in the stand. The only essential ingredient for maintaining tree freshness is plenty of clean water in the tree stand.
North Carolina growers depend on retailers for satisfied customers. Paying attention to the suggestions above can eliminate or minimize potential problems. Also, complete and honest communication between growers and retailers early in the season can help avoid serious problems later.
Recommendations for use of agricultural chemical brand names and any mention of commercial products or services does not imply endorsement by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned in this publication.