Monday, August 22, 2011

Collecting softwood cuttings

As discussed in a previous post, blueberries can be easily propagated in summer from leafy softwood cuttings by using an intermittent mist system to keep the cuttings from drying out during the six- to eight-week rooting period.  However, a specific stage of shoot growth must be selected for cuttings, because not all leafy shoots will root -- those that are too old will tend to form flower buds rather than roots, and cuttings from shoots that are too young and succulent will wilt before rooting can occur. The photos below illustrate when and how to collect and stick softwood cuttings.

Timing:  Collect cuttings when shoots are 10-12 inches long and semi-hardened.  In southeastern NC,  this occurs in late May and again in late July or early August:

Blueberry bush in early August with suitable shoots for propagation

Cuttings can be snapped off by hand or clipped with pruning shears

Pinch off the top of the cutting and remove the lower leaves

Age of cuttings:  Select cuttings with leaves that are intermediate in color between the darkest older leaves and the palest young shoots.  Softwood cuttings should be immature but not succulent.  Cuttings that snap easily when bent are too young -- the cuttings should be bendable and becoming woody.

Leafy shoots from oldest to youngest.  The two in the center are suitable for propagation.
Softwood cuttings of the proper stage are bendable but do not snap

Shoots that snap easily when bent are too succulent for outdoor propagation beds

Handling:  Collect cuttings early in the morning if possible, to minimize wilting.  Once collected, cuttings are susceptible to wilting and must be kept moist and cool. Sprinkle with water and store in a cooler with ice until ready to stick the cuttings in the rooting bed.  Caution -- direct contact with too much ice can damage cuttings -- keep them cool but not icy.

Take a cooler and water to the field to keep cuttings from wilting

Sticking cuttings:  Cuttings are stuck into six- to eight-inch deep rooting beds filled with aged milled pine bark. Stick the cuttings 1.5 to 2 inches apart in rows by cultivar.  Approximately half the length of the cutting should be in the bark, with only the leafy section above the bark. The mist system should be running during this process so that the cuttings are never allowed to dry out.

A measuring stick is used to space the cuttings evenly across the bed.

Cuttings are stuck approximately half their lengh in the bark

A commercial rooting bed partially filled with cuttings

Cuttings typically root within six to eight weeks.  Once fully dormant, the cuttings can be dug and either potted, or planted directly into the field.  Most nurseries and commercial growers pot rooted cuttings and grow them out for a year prior to selling or setting in the field.

For further reading: 
Krewer, G. K. and W. O.Cline. 2003. Blueberry Propagation Suggestions.
Bilderback, T. E., R. E. Bir and M. A. Powell 1993.
A Simple Intermittent Mist System for Propagation.