Does Frost Kill Cottonwood Cuttings?

Protect Cuttings When Temperatures Fall

• Because the warmer end of the cottonwood's hardiness range rarely experiences hard frosts, starting cuttings outdoors in these zones in winter is generally safe in zones 8b through 9. If forecasts call for temperatures to unexpectedly dip below freezing, moving the cuttings to a sheltered rooting structure will protect them from possible damage. Any shelter that's out of the freezing temperatures will do, whether it's a garage, greenhouse or even a covered back porch.

  In USDA zones 3 to 8a, using either a hot bed or a cold frame will provide the necessary protection and will also aid in faster root development, allowing the cuttings to grow to transplanting size more quickly.

Selecting Cuttings for Success

• Selecting cottonwood cuttings carefully will result in greater success at propagation. Cuttings should come from a side branch that is between 8 to 10 inches in length and one-quarter inch in diameter. The wood should be free of damage caused by insects and diseases and it should have several leaf nodes on the tip and on the sides. Each cut should be made at a 45-degree angle one-eighth of an inch under a leaf bud. Using a sharp propagation knife will eliminate ragged edges. Be sure to begin with cutting tools that have been disinfected, such as by soaking in a 10 percent chlorine bleach solution for a couple minutes or wiping with rubbing alcohol.

Prepare Cuttings Properly

• Cottonwood cuttings will root within one to two weeks. Successful rooting will occur more quickly if the base of the cuttings are wounded before they are placed in the rooting medium. Using a sharp, disinfected, propagation knife, scrape off the bark for about half an inch at the bottom of the cutting. A 50-50 mixture of medium grade perlite and coarse sand provide a good rooting medium for cottonwood cuttings. They can be placed in standard nursery pots and situated in a sheltered location. If a cold frame or hot bed is not available, place them against a south-facing wall.

Tips for Transplanting

• Sheltering the cuttings until after frost danger is past will ensure the formation of healthy young trees. Cottonwood cuttings need moisture to thrive, but allowing the top two inches of the rooting medium to slightly dry out between waterings will prevent the cuttings from rotting.

  Move the cutting to a less sheltered location one week before it is to be transplanted to its permanent location will get it used to outdoor growing conditions.

  Cuttings should be planted bare-root in full sun in fast-draining, moist soil.