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Plant Answer Line Question

Keywords: Philadelphus, Failure to flower, Pruning shrubs, Fertilizers

I just bought a house with a garden which has good bones, but has been untended for a long time. I believe the garden has 4 Philadelphus X virginalis 'Minnesota Snowflake' plants. They are deciduous in the winter, and they have greened up nicely in the summer. They are about 6 feet tall. On the 4 plants, this first summer, I've only seen 2 flowers. Can these shrubs be salvaged by using a blooming (high in phosphorus) fertilizer? Or do they need something else?


The three things I would ask about Philadelphus with few flowers:

  • Are they in full sun? (Sun is needed for best flowering results.)
  • Have they been pruned and, if so, when? (Pruning is best done in late summer, after flowering.)
  • Are they growing near a lawn or other area which receives fertilizer that is higher in Nitrogen (N) than Phosphorus (P) or Potassium (K)?

I would recommend that you test the soil before embarking on a plan of fertilization, unless you are adding a mulch such as compost, which releases its nutrients slowly. Philadelphus is usually considered a light feeder (i.e., it doesn't require a lot of supplemental fertilizer).

As far as a future pruning regime for the shrubs, Jacqueline Heriteau's Complete Trees, Shrubs & Hedges: Secrets for Selection and Care (2005) says that Philadelphus "blooms on the previous year's growth. A light annual pruning of older branches right after flowering keeps mock orange shapely and productive. Branches more than five years old should be removed in winter or early spring."

Date 2018-03-14
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May 31 2018 13:14:08