I live in Chester NS and have a mature (20 year) Star Magnolia which blooms prolifically every May , around 10 -12 of May, including this past May It is in a sheltered spot and has lots of room. I noticed that is suddenly has dropped hundreds of its buds, which all look fine. The tree and all its leaves look fine. We did have a very heavy frost this year on June 6th , could this be the cause? Thanks.
Thank you for contacting Toronto Master Gardeners concerning bud drop of your mature Star Magnolia (Magnolia stellata).
Since your tree bloomed successfully in May, I presume that it is the buds destined for next year’s flowering that have fallen.
For optimum care, the tree prefers moist organic soil in full sun and it is recommended to mulch, to retain moisture, with organic material such as compost, composted pine bark, etc. keeping it away from the trunk(s) by about 10 cm or 4 inches in order to prevent the mulch from harbouring insects or causing damage to the trunk. Blossoms are susceptible to frost or wind which may have affected the dropped buds.
Magnolia scale (Neolecanium cornuparvum) is almost its only pest. The Missouri Botanical Garden claims that salt spray can cause bud death and twig dieback and salt in the soil is slow acting and may not affect plants for many years and, of course, you will be aware if this is a possibility.
Toronto Master Gardeners has previously responded to a magnolia bud drop question that might be of value in your enquiry with a number of factors to consider. http://www.torontomastergardeners.ca/askagardener/magnolia-bud-drop/
An interesting fact is that Star Magnolia is pollinated by beetles, and it’s woody carpels are strong to protect them from damage by the beetles.
We wish you well in your continuing flowering success with your lovely tree.