General Guidelines for Storing and Planting Aspen Cuttings
By Brad Bender
What is best cutting depth?
You can plant 10" dormant cuttings with the tops almost flush to the ground to about an inch exposed. The buds can be buried over an inch deep on the stem and they find their way up to the surface to sprout. Often they are hand planted into ground that has been tilled and spaded so it is very fluffy and easy to hand plant without tools. Out in the Pacific Northwest they were planted on tight spacing with long 18" cuttings with a couple inches exposed to get multiple stems for biomass. A 7-acre Upper Michigan 8 x 7 spaced site was planted with the Whitfield tree planter. They kept the cuttings between flush and 1-inch high with no attention to the upper bud position.
How do you store aspen cuttings and bare root trees?
Some Northern Poplar nurseries harvest their cuttings in December because they have labor available and snow is not drifted too high for harvesting (vs. late winter harvest). They store their processed cuttings in sealed plastic bags (4 mil?) at about 28 F. For them, its somewhat a logistics concern for their business schedule and location.
Ron Zalesney's paper suggesed that late winter is the best time for harvesting cuttings, but he emphasizes that clone variation might exist (see: http://www.nrs.fs.fed.us/pubs/3233). It is only one research paper and all that implies. FBIC harvests in late winter (February/March) and store them for a shorter period at 34 F. using 4 mil sealed bags and no added moisture.
Bare root seedling storage has many variations also. The Toumey nursery lifts stock in early winter (November?) and does "overwinter frozen storage" in sealed, lined paper bags with no added medium (moss). Again, this is a logistics issue since they need to ship seedlings to southern region 9 when the ground is still frozen in the U.P.. Supposedly, their 3 ply bags retain moisture, but allow respiration gases to be exchanged. The bags achieve 100% humidity inside, negating any need for added moisture holding media (moss).
Other nurseries lift in the spring and use various packaging: plastic bag lined boxes, 3 ply bags as above, jelly roll treated paper with spagnum moss on roots. Spring lifted trees are often stored above freezing. Some use moisture holding packing media, others do not.
Pat McGovern stores dormant aspen cuttings in a refrigerator using ziplock freezer bags at about 30 degrees F. He noted that the cuttings can be stored this way for two to three months. The cuttings are usually stored dry but will have ice flakes inside the bag and seem to grow well when planted after a 24 hour soak in water.
FBIC uses moistened shredded paper in 3 ply bags to store spring lifted seedlings at 34 F. Mold can start in long term storage (over 2 months +/-). I have added a tiny bit of water to seedlings I thought maybe dessicated a bit before getting processed. Some say this encourages mold.
There's tons of research papers on seedling lifting and storage. We think that the late fall harvesting and overwinter frozen storage is mostly due to logistics vs. being a better method to ensure seedling survival. In the old days (maybe still), nurseries would late-fall lift seedlings, then "heel In" back into the nursery soil. This resulted in condensing them, getting some of the labor done, and making them more easily available in the spring wet period.
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