I live in Toronto , upper beaches. I need help on the best step to transplant part of my mock orange. I have to move it from its current location and hope to trim him down before moving it in September. For the best survival outcome , what would you recommend I do? Please take a look at the pics, it is just too big , how short should I trim it ? Would I be able to divide it ? Would it flower the next spring ?
Thank you for contacting the Toronto Master Gardeners concerning your mock orange.
Mock Orange (Philadelphus coronarius) benefits from annual pruning to encourage strong healthy shoots and improve flowering. Annual pruning also prolongs the life of these plants. Mock Orange blooms on the previous year’s growth, also known as ‘old wood’. Therefore, they should be pruned immediately after flowering, because if you wait too long to prune, you run the risk of cutting off the buds for next year’s flowers.
Normally it is best to transplant a shrub in the fall when it goes dormant so September would be the optimal time. If the mock orange is large, tie up its branches to keep them safe during the procedure.
When you are ready to transplant choose a cool and overcast day, and work as quickly as you can. Water your plant thoroughly the day before you plan to move it. When you dig your plant up, try to disturb it’s roots as little as possible, and bring as much of the root as you can with the plant. The next step is to make sure that the planting hole is large enough. The new hole should be twice as wide as the existing root ball. Put the plant into the hole and fill it approximately halfway with water, permitting the water to run out. This settles the soil surrounding the roots. Fill the hole with soil , and press down gently around the plant to ensure there are no pockets of air in the soil. Water thoroughly, and make sure you continue a program of watering daily for the next few weeks to help your plant establish itself.
The following web site will give you detailed instructions on how to transplant shrubs with the greatest success
https://www.clemson.edu/extension/hgic/plants/landscape/shrubs/hgic1055.html
Proper pruning will keep your mock orange neat and tidy as well as prolonging it’s life. Again this plant should be pruned after it blooms. Dead or damaged wood can be removed at any time. These stems should be removed right to the ground or to their point of origin. You could remove dead or damaged wood at the same time as you do annual pruning, right after flowering, so that all of your pruning is done at the same time.
As Mock Orange shrubs mature, they can get overgrown. This can be prevented by cutting back up to 20 percent of aging stems to near the base each year. If a Mock Orange is severely overgrown, there are two ways to rejuvenate it. The first is to rejuvenate in stages, over the course of three years, by cutting one-third of the oldest stems down to the ground, at the time that you do your annual pruning, each year for three years. After three years, you will have a healthier looking shrub. The second way is drastic pruning, which is cutting all of the stems to ground level in the spring. You will not have flowers that year and maybe not the next, but you will soon see healthy growth at the base as the shrubs quickly grow back.
It should be noted that transplanting your shrub and pruning it now will impact the blooms next spring. However with proper care you should see you mock orange in full bloom the following year.