Pollen contamination and mating system of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) clone banks used as an interim seed orchard near Nanaimo, B.C., were estimated. Pollen contamination (m) from surrounding clone banks and natural stands ranged from 0.44 to 0.89. Overall contamination over 2 years was estimated to be 0.65. Pollen contamination varied significantly over 2 pollination years. Multilocus outcrossing rates (t) of four clone banks over 2 years ranged from 0.51 to 1.09, with an unweighted mean outcrossing estimate of 0.72. Outcrossing varied significantly among clone banks and pollination years. An excess of homozygotes suggests that these seed may be inbred. Although pollen contamination and inbreeding may be a problem in these clone banks, the seed may still be useful operationally.

Application. Girdfing in combination with a single stem injection of the growth regulator gibberellin m4/7 call be a highly cost-effective treatment for enhancing seed yield in Douglas-fir seed orchards. Diminished tree vigor and flowering response to biennial retreatment can result, however, unless trees are properly managed to minimize the physiological stresses associated with treatment and the heavy cone bearing which follows. Alleviation through irrigation and possibly fertilization of compounding water and nutrient stresses following treatment and during the off-treatment year to will speed the recovery and should enable trees to be safely retreated on a biennial basis.Abstract. Twelve-to 17-year-old Douglas-fir grafts, which in 1985 received no treatment,

This experiment compared the rooting response of cuttings taken monthly from slash pine (Pinuselliottii Engelm.) clones maintained in a greenhouse environment and in a field environment. Greenhouse cuttings rooted better in all months except for the first May collection. Seasonal variation was less pronounced in cuttings taken from the greenhouse-maintained plants, and May collections gave the highest percentage rooted from both locations. Average rooting by clone varied from 47 to 4% for field tests compared with 63 to 19% for greenhouse tests. Environmental effects on rooting, known to be critical on ramets in the propagating bed, are shown to be important also on the ortets.

Experiments on field-grown and potted trees investigated the effect of timing of gibberellin A3 treatment in relation to natural day length on flowering and sex expression in Chamaecyparisnootkatensis. When gibberellin A3 treatment began was more important than the number of weekly sprays (two to eight), and the optimal time of treatment was similar for promotion of seed and pollen cone buds. The optimal treatment time was independent of photoperiod or its direction of change, but instead appeared to be related to a specific stage of ontogeny during early development of the bud apex. Trees growing at progressively lower elevations attained this stage earlier in spring, suggesting that the mechanism triggering initiation of bud development involved heat sums. A higher concentration of gibberellin A3 was required to initiate seed cone buds (200 mg•L−1) than pollen cone buds (100 mg•L−1), and the average weekly dosage was more important than whether gibberellin A3 was applied weekly or biweekly. Young, potted trees within a greenhouse flowered more profusely than larger but similarly treated field-grown trees, indicating that the species is a good candidate for containerized seed orchards.