Container Production for Living Christmas Trees - Department of ...

container productionwinter 2009great lakes christmas tree journalContainer Production for Living Christmas TreesBert Cregg, Wendy Klooster, Amanda Taylor, R. Thomas Fernandez and Pascal Nzokou, Michigan State University, Departmentof Horticulture, Department of ForestryLiving Christmas trees are an increasinglypopular niche market for manyChristmas tree growers and tree nurseries.Although no official statistics areavailable on sales of living Christmastrees, a walk through a garden center ora perusal of specialty catalogs such asJackson and Perkins shows an everincreasingarray of living Christmas treesavailable. Several university extensionservices such as Clemson and Purduenow publish guidelines for care and handlingof living Christmas trees for consumersthat want to plant their trees afterthe holidays. In the western United States,companies now offer “rental” Christmastree services that bring living trees intohomes for holiday display and then pickup the trees after Christmas and plantthem in parks and schools.Marketing living trees that consumerscan plant after the holidays is not newand many Christmas tree growers havedug and sold a portion of their crop asliving trees for years. The reasons consumerschoose living trees are varied;Table 1. Approximate Weight of Soil in Root-balls of Field-dug ConifersTree height Minimum Root-ball diameter 1 Root-ball weight 2(feet) (inches) (pounds)3 18 60–704 20 80–1005 22 110–1306 24 140–1707 26 180–2108 28 230–260some consumers consider living treesmore environmentally friendly than cuttrees,some like the ‘two-for-one’ aspect ofChristmas trees that can also be plantedin the landscape, some plant trees tomark special occasions such a child’sfirst Christmas. A major challenge forconsumers purchasing field-dug trees,however, is that the root-ball of even amodest-sized living tree can weigh 100lbs or more (Table 1).Container-grown conifersContainer production systems offergrowers a means to produce lighterweightliving Christmas trees that are easierfor typical consumers to handle.Growing Christmas trees in containersfollows the trend found in the landscapenursery market. According to a 2007 U.S.Department of Agriculture survey, containerproduction accounted for 53% oftotal landscape conifer nursery productionin 2006, up from 46% just three yearsearlier. At the same time, balled and burlapproduction dropped from 49% to 42%of the market.Moving from field production to containerproduction may seem like an easytransition , but the differences between37

container productionwinter 2009great lakes christmas tree journalMSU graduate research assistant Amanda Taylor is investigating growth and water use of container-grown conifers in response tocyclic irrigation.38field-growing and container-growing areso vast the best advice for would-be containergrowers may be, “Forget everythingyou know.” While all of the subtleties ofcontainer production can fill volumes,the three most important factors growersneed to consider are: container substrates,irrigation management, and nutritionmanagement. These factors can beconsidered as a ‘three-legged stool’ andeach one must be properly managed toproduce a quality crop.Container substratesOne of the biggest challenges forChristmas tree producers accustomed tofield production is understanding theimportance of container substrates.Choice of substrates will influence allother aspects of managing the crop.Many first-time container growers are surprisedto learn that container substratestypically do not contain any soil. Themost common elements are light-weightmaterials including pine bark, Douglas-firbark, peat moss, perlite, coconut hullsand composted materials such as ricehulls. In the southern U.S. several universitiesare researching the use of woodchips as an alternative to pine bark,which is becoming more expensive as itis diverted to other uses such as fuel andlandscape mulch. Regardless of thematerial chosen, the desired propertiesof container substrates are: moistureholding capacity, porosity (adequate airspace and drainage), weight (lighter isusually better), cost, and availability. Fora wide range of plants, mixtures of pinebark and peat moss provide an excellentcontainer substrate. We recently comparedgrowth of four conifer species(Fraser fir, Colorado blue spruce, Blackhills spruce and eastern white pine)planted as 2+2 transplanting into 3-galloncontainers. The plants were grown fortwo years in three ratios of pine bark andpeak moss (90% pine bark: 10% peatmoss, 80:20 and 70:30). Trees of all fourspecies grew well in the intermediate(80:20) mix (Figure 1). The fir andspruce trees also grew well in the heavy(70:30) mix while pines grew well in thelight (90:10) mix.Irrigation managementProper watering is essential to containertree production. In contrast tofield production, where rainfall may providesufficient moisture, container-growntrees must be irrigated because of theirlimited rooting volume. Typically container-growntrees are watered every dayduring the growing season, particularly inmid-summer when temperatures are attheir peak. Depending on the size of thecontainers, irrigation may be provided byoverhead systems or by drip or microsprinkler(spray stakes) systems.Typically landscape container nurseriesuse overhead for 5-gallon containers orsmaller but some nurseries will use drip

container productionwinter 2009great lakes christmas tree journal40Figure 1. Averagestem caliper of livingChristmastrees grown in3-gallon containersfor two yearsin substrates withvarying ratios ofpine bark andpeat moss.Figure 2. Averageone-year calipergrowth of easternwhite pine treesgrown in 3-galloncontainers at threeirrigation levelsapplied by dripemitters or spraystrakes. Dailyirrigation amountapplied once dailyat 6 am or appliedas 4 cycles at 6 am,10 am, 2 pm and6 pm.Figure 3. Averagetwo-year heightgrowth of livingChristmas treesgrown in 3-galloncontainers inresponse to varyingrates of fertilizer.Fertilizer wasapplied as controlledrelease product(Osmocote 15-9-12 (N-P-K) 8-9month Northernrelease, Scott, Inc.)or spray stakes on smaller stock especiallyin Pot-in-Pot systems. The advantage ofoverhead irrigation is the low initial costand ease of installation. The disadvantageof overhead irrigation is the lower wateruse efficiency compared to drip or microsprinklerirrigation since overhead systemsirrigate the space between plantsand they also lose more water to evaporation.Drip and micro-sprinkler systems arevery efficient at applying water to theplant root zone but are more expensive toinstall than overhead systems.Maintenance can also be an issue withdrip or micro-sprinklers; since each treehas its own emitter or spray stake, workersneed to walk tree rows regularly to inspectand replace emitters that are clogged ordamaged by animals.As noted earlier, growers can improvethe efficiency of water use by using dripirrigation or spray stakes instead of overheadirrigation. Water use can be furtherenhanced by cyclic irrigation. Researchin the South has shown that wateringnursery crops in small pulses 3 or 4 timesa day can improve plant growth comparedto applying to same total amount ofwater once a day. We recently installedan irrigation trial of container grown conifersat the MSU Pot-in-Pot ResearchNursery. Preliminary results from the firstyear of the two-year study indicate thatapplying four 4-minute cycles of irrigationper day can improve growth of livingChristmas tree species compared to treesreceiving the same daily irrigation amountapplied as a single 16-minute cycle(Figure 2).Nutrition ManagementFertilization is the third essential componentof container production. Sincecontainer media are essentially soil-lesssubstrates, growers must account for allessential plant elements in their fertilizerprogram. This is in contrast to field productionwhere growers may only need toadd nitrogen or specific deficit elementsto produce a successful crop. The mostcommon approaches to fertilizing con-