I planted a lovely star magnolia in my Dublin garden a few years ago, but it’s failed to flourish and has yet to flower (it was in full flower when I bought it). It’s growing in a slightly shaded spot near a boundary wall. What should I do?
N Quinn, Dublin
Star magnolia (Magnolia stellata) is a very popular species of this highly ornamental genus of hardy, spring-flowering shrubs, with large, pale, star-shaped flowers that open from silky buds on its bare branches around this time of year. More compact than a lot of the other kinds of more sprawling magnolias traditionally seen growing in large, established suburban Dublin gardens, such as Magnolia campbellii and Magnolia soulangeana, it slowly forms a bushy shrub or small tree of about 2m-3m in height and spread.
It needs a sheltered spot in sun or light shade, which is exactly what you’ve given it, so it doesn’t sound like this is the problem. However, as is true of most species of magnolia, it needs a deep, damp but free-draining, humus-rich, neutral or acidic soil. If yours is tending towards being dry and alkaline, as many Dublin gardens are, then I think this is most likely to be the issue.
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To help matters, I’d suggest regular, generous biannual mulches of well-rotted manure or homemade compost around the roots in autumn and then again around this time of year, which will gently lower the pH. This additional organic matter will also build up humus levels in the soil, which will help with fertility levels as well as making it more moisture-retentive during dry spells. Early spring is also a good time of year to boost healthy growth by sprinkling some handfuls of an organic ericaceous fertiliser around the base of the plant.
Finally, bear in mind that magnolias dislike being pruned, which also runs the risk of inadvertently cutting out the branches on which the flower buds have been slowly developing since the previous spring. If you do have to prune it to keep it in shape in the years to come, do this immediately after flowering.
