The way to Prune Sister Theresa Hydrangea

The way to Prune Sister Theresa Hydrangea

Grown in U.S. Department of Agriculture plant hardiness zones 6 through 9, “Sister Theresa” hydrangeas (Hydrangea macrophylla “Sister Theresa”) grows up to 5 feet tall and 8 ft wide. “Sister Theresa” is a variety of mophead hydrangea famous for its white, ball-shaped blossom clusters. Mophead hydrangeas naturally develop in a curved form, requiring little pruning to keep contour, especially in young plants. As “Sister Theresa” matures, pruning requirements increase to sustain a balance between old and new wood. “Sister Theresa” along with other bigleaf hydrangeas bloom on old wood and has to be pruned around July following the flowering period.

Remove all dirt and debris in your bypass pruners, then dip the blades in 70-percent isopropyl rubbing alcohol to disinfect them so you do not accidentally spread disease for your hydrangeas.

Cut the dead blossom flowers back to a leaf node below the blossom cluster, cutting just above the node, if wanted. As an alternative, you can leave the dead blossoms on the plant over winter to add a bit of texture to your winter garden.

Cut out all dead, diseased or broken stems. Cut dead stems close to the floor and cut broken comes back to the nearest healthy leaf node. Diseased stems must be cut at least 6 inches below the diseased area. Disinfect the pruners with alcohol each time following cutting diseased branches before carry on your pruning efforts.

Cut all thin or weak stalks back to the bottom. These will be the stems, typically found in the middle toward the base of this plant, that did not have the time to fully develop and harden off before winter.

Remove any rubbing or crossing stem to open up the inside of the plant to air flow. Choose the very best of the 2 branches and cut another weaker stem close to the ground.

Cut the tips of longer stems just above a leaf node to bring the stems in contour with the rest of the plant. Remove no more than one-third of the entire length of this stem.

Renew the old wood in a three-year pruning process in the event the plant is more than five years old and appears overgrown with wood. In the initial year, remove one-third of the old divisions, cutting them back to the ground. Cut another one-third of those old branches in the second summer, then remove the rest of the one-third of the previous branches in the next summer. Select stems to prune that are spaced evenly throughout the plant so the flowers that bloom on the remaining wood will be dispersed evenly around the cylinder.

Clean up the plant debris from across the base of the plant, then spread a 2-inch layer of humus material, such as leaf mould, as mulch around the base of the plant. Avoid pushing the humus mulch directly against the plant comes.

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