How to grow Magnolia

Pruning and Deadheading

Magnolias require little in the way of pruning and are best left to grow naturally, aside from a light tidy after flowering if necessary. This means removing any dead, diseased, damaged, or badly placed growth.

An mishappen or overgrown deciduous magnolia can be renovated over a three-year period. This means removing only a third of the branches at a time to avoid causing too much stress to the plant.

Watering

Magnolias should be regularly watered during their first few years in the ground, after which they should be largely self-sufficient other than in hot, dry conditions. It is important that magnolias are not allowed to dry out fully, so do remember to keep an eye on this. Magnolias grown in free-draining soil need more attention when it comes to watering, and will benefit from an extra mulch or two throughout the year to help lock in the moisture (see ‘Feeding’ section below). The same goes for magnolias grown against a wall, which can be sheltered from rain.

Container-grown magnolias have less access to moisture so need to be regularly watered throughout every growing season. Allowing the top couple of centimetres of compost to dry out between watering is a useful rule of thumb to help avoid overwatering. Use your finger inserted into the compost to check. From mid-autumn, the British climate tends to take over watering needs, though do remember to step in in the event of an unseasonably dry spell.

Feeding

To give them the best possible start, feed magnolias for their first few years in the ground with a general purpose granular feed applied to the surface of the soil and lightly worked in (known as a ‘top dress’). This is best done in late winter, along with a mulch of well-rotted organic matter (i.e., a layer of manure or garden compost applied to the soil around the plant). This has the added benefit of suppressing weeds and locking in moisture.

Once your magnolia is well established an annual mulch should provide sufficient nutrients, however apply a top dress as above if ever an extra boost is needed.

Container-grown plants rely even more on the gardener for nutrition. Get off to a flying start by making sure you use a good quality compost, then throughout the growing season (March to September) apply a liquid feed at regular intervals according to its instructions. An annual top dress is also advisable. Each spring, scrape off the top 5cm of compost and replace with fresh compost containing a little general purpose granular feed.

Cold Protection

If you live in a colder region, you may be best giving H4 and H5 rated species and cultivars a protected spot against a warm, sunny wall.

A late frost can damage magnolia flowers, so it is worth familiarising yourself with the average weather patterns in your area and choosing a species accordingly. For those further north, a later flowering variety is best. In milder areas, many of the earlier varieties are also an option.

Like all plants, those grown in containers can be more vulnerable to the cold. In the event of very low temperatures, it can be worth wrapping pots with hessian or fleece (this will protect the pot from cracking too).

Pests and Diseases

Magnolias are usually problem-free, though there are a couple of fungal diseases to be aware of.

Honey fungus tends only to be a problem where there is a heavily wooded area nearby, so is thankfully not a likely problem for most home gardeners. Phytopthora is a root rot which can occur on heavy, wet soils. Both will cause similar symptoms of dieback and sparse foliage, and unfortunately little can be done other than removing the affected specimen and replacing with a known resistant alternative. Quince (cydonia) and parrotia are rarely affected by either disease and make good magnolia substitutes.