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  • Author or Editor: Gary A. Chastagner x
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On placement of their freshly cut bases in water, cut douglas-fir Christmas trees, which had dried to −2.0 or −3.0 MPa, rehydrated to about −1.0 MPa within 24 hr, and limited needle loss occurred as their water potential gradually decreased to − 6.0 MPa during display. Only 90% and 75% of the trees, dried to water potentials of −4.0 or −5.0 MPa, respectively, rehydrated when placed in water, and water potentials of these trees increased to −1.9 and −2.8 MPa, respectively. About 40% of the trees dried to −4.0 or −5.0 MPa exhibited severe needle loss, characterized by complete abscission of fresh-appearing needles from the stem within a few days of rehydration. These data indicate that douglas-fir has a threshold water potential between − 3.0 and − 4.0 MPa. When trees were allowed to dry to or below this threshold, tree quality was significantly reduced.

Open Access

Needle retention is an important trait when selecting for high quality Christmas trees. Nordmann fir [Abies nordmanniana (Stev.) Spach.] is generally considered to have good needle retention, but recent research has shown that when cut trees are allowed to dry, significant needle loss problems can develop. This has the potential to limit the use of this species in situations where trees are harvested early, shipped long distances, sold in warm weather markets and displayed for extended periods of time. A set of 39 provenances where tested to identify provenance differences in needle retention. Branches where collected in two consecutive years in October in 1999 and 2000 and November 2000. Small branch samples where cut and displayed indoors under controlled conditions and allowed to dry. Strong provenance differences in needle loss were seen for all three test dates. No significant interactions were seen among the October collections, but significant rank changes occurred from October to November. Predicted (BLUP) provenance mean values ranged between 11% and 27% for needle loss when branches where allowed to dry, averaging all three tests. Despite only one test location, the study clearly indicates that it should be possible to select for provenances with generally better needle retention characteristics.

Free access

Moisture and needle loss characteristics were similar for noble (Abies procera Red.) and Nordmann fir [Abies nordmanniana (Stev.) Spach.] Christmas trees that were displayed in water. After 42 days, trees still had xylem pressure potentials above -2 MPa. In addition, trees that were displayed in water had very little needle loss. When trees were displayed dry, noble and Nordmann fir had similar rates of moisture loss, drying to about -6 MPa in about 3 weeks. Although there was very little needle loss from any of the noble fir trees that were displayed dry, some Nordmann fir trees began to shed large numbers of green needles within 3 to 5 days, which significantly reduced postharvest quality. Unless sources of Nordmann fir are identified that have good needle retention characteristics, the needle loss problem observed when trees dry to about -3 MPa has the potential to limit the use of this species as a Christmas tree in the United States.

Free access

Postharvest moisture and needle retention of boughs was examined for four Danish and five U.S. provenances of noble fir grown in Denmark. Boughs were displayed indoors under controlled conditions, and data were collected relating to rates of moisture loss and needle retention. Small current-year shoots had moisture and needle loss patterns similar to larger bough material. Postharvest quality of the Danish and U.S. provenance boughs was very similar. There was also a high correlation between the moisture level of the boughs and shoots, indicating that it should be possible to use small shoots to assess differences in moisture retention in future tests.

Free access