How to grow a deciduous magnolia tree

Looking for a feature tree with some serious ‘Wow!’ impact? The deciduous magnolia will deliver.

What you need to know about a magnolia

Name: magnolia, deciduous magnolia, saucer magnolia (most often Magnolia x soulangiana var., but other species and cultivars are often just sold as Magnolia followed by the hybrid or cultivar name, e.g. Magnolia ‘Vulcan’)

Plant type: small- to medium-sized deciduous tree.

Height: to 8m tall × 5m wide with many smaller varieties.

Foliage: oval shaped, quite broad, around 15cm long × 10cm wide, definite pointed tip. New growth bright, limey-green that ages to dark green, paler beneath. Sometimes just slightly furry.

Climate: warm temperate in cooler locations and cool temperate in warmer spots. Sub-tropical in cooler, elevated locations.

Soil: rich, free-draining, prefers acid conditions (see soil notes on pH).

Position: full-sun, must have protection from wind.

Flowering: flowers in late winter or early spring, generally on bare wood before new leaves form.

Feeding: annually with a quality controlled-release fertiliser that is balanced for acid-loving plants.

Watering: must have reliable moisture during periods of flowering and leaf growth and in hot weather.

Deciduous Magnolia

Appearance and characteristics of a magnolia

Spring flowering magnolia trees have their own special allure. Their gorgeous flowering display is like a joyful shout-out from nature, signalling that winter is behind us. There is one kind of tree that puts on the biggest, boldest and most breathtakingly beautiful display—the deciduous magnolia. Its flowers are made up of petals that are 12cm or more in length, making them nothing short of spectacular. The flowers are often described as tulip-like, as they start with an upright, slender form before opening to a near saucer-like shape. The colours are just divine. A regular M. x soulangiana is mainly white with various levels of purple towards the petal base. There are also deciduous magnolias with pure white blooms and all manner of shades, including delicate, slightly fragrant yellows to very deep, luxuriant purples. The impact of this flowering display is amplified by the fact that it all happens on bare wood before the new season’s foliage has started to open.

The deciduous magnolia will generally have one central trunk with a number of solid lateral branches creating a spreading form. This can give the impression that the tree is multi-trunked. Its form is naturally quite neat and tidy, and the tree is often almost as wide as it is tall. The classic M. x soulangiana can become large with age, up to 8m tall × 5m wide, but most magnolias are smaller than this, with 5 × 3 being more typical at 10 to 15 years. Many of the newer varieties have growth habits that are around half that of a typical deciduous magnolia.

Flower and leaf buds develop on the tree over winter and are protected by furry protective coverings. The flowers can take week to fully open. Flowering time and duration will depend on the variety and location. The new leaves will follow shortly after flowering, or may start appearing while flowers are still present.

The canopy of the tree is quite dense when it is healthy and happy. The leaves start very soft and bright green and then age to a slightly leathery or thick papery feel. This tough appearance is deceptive, as leaves will be easily damaged by hot or drying winds. In autumn the leaves will wither and brown before falling. As the older bark of the tree is a smooth silvery grey, the tree makes a beautiful specimen even when bare in winter.

Uses for magnolia

Magnolia can be grown for several purposes, including:

  • feature tree

  • great sustainable choice, offering cooling winter shade and letting in warming winter sun

  • beautiful spring flowering display.

How to plant and grow magnolia

Magnolia grows best in full-sun to part shade. It must be protected from strong winds, or the flowering display can be quickly lost, and foliage damaged. Magnolias may tolerate temperatures as low as –5˚C, but frost protection is essentially, especially for younger trees. In hotter zones they must be planted in the coolest possible spot, as they need winter dormancy and protection from strong heat.

For best results, plant in a good quality, slightly acid, deep soil with additional organic matter such as quality compost or well-composted manure. However, magnolia will grow well in regular garden soil, provided drainage is good and it has reliable moisture during flower and leaf development and across the warmer months.

Soil notes on pH

Magnolia, both evergreen and deciduous, is described as an ‘acid-lover’—that is, it likes soil that is classed as more acid. Soil acidity or alkalinity is all about the pH level of the soil. The pH scale runs from 0 to 14. Neutral soil has a pH of around 6.5 to 7. Slightly acid soil has a pH of around 6 to 6.5. Most garden plants like soil leaning towards the acid side at around 6.5, but magnolias tend to like a pH from 5 to 6.

So, what does this mean if you have “normal” garden soil? Realistically, not much. You can still plant and grow magnolia with great success in regular garden soil. The main impact of small variations in pH is that it affects the availability of various nutrients. If a soil is not adequately acid, then nutrient deficiencies may occur. Most of these can be overcome by using a fertiliser that has been blended for acid-loving plants. In addition, maintaining biologically active and healthy soil, may not amend pH, but the resulting microbial activity can improve nutrient availability.

If, on the other hand, your soil is distinctly alkaline (over pH 7), you will need to look at amending the soil pH or importing soil before planting your magnolia. Amending soil pH is a tricky, potentially complex and ongoing exercise. There is no one-off fix, you’ll need to reapply amendment additives at least annually.

You can test your soil using a simple pH test kit. Just remember that the pH of each area will be different. Talk with a plant specialist in your local nursery for more advice.

Magnolia planting tips

1. The plant may be quite whippy (tall and thin) when bought, so will need staking during root development. Use at least two stakes.

2. Improve soil with a quality compost or well-composted manure at planting time.

3. Mulch well and keep mulched. This is especially important in warm temperate and sub-tropical regions.

Caring for magnolia

Fertilise your magnolia annually in spring with a quality controlled-release fertiliser that is balanced for acid-loving plants. Supplement feeding with an organically-based product such as a seaweed tonic as the flowers and foliage develop. Allow fallen leaves to remain around the base of the tree to mulch and naturally break down.

How and when to prune magnolia

It is best to avoid pruning most deciduous magnolias, as this can trigger rapidly growing vertical shoots called “water shoots”. These shoots can ruin the form of the tree, and are also very weak and prone to breaking off.

Most deciduous magnolias will be grafted, so look for any shoots arising from beneath the graft and prune them off. If you don’t do this, these shoots can start to dominate, meaning the tree you bought will likely die back and the resulting tree will not have the flower colour or form of the tree you purchased.

Diseases and pests

You’ll encounter very few problems with a deciduous magnolia. If you find that your tree seems to have skipped a flowering season after looking like buds were developing, you may find that possums are the culprits. Some possums can develop a taste for the plump young buds. If this happens, you may need to spray the tree with an animal deterrent the next season as soon as buds start developing, or net it until flowers open.

How to propagate magnolia and growing magnolia from seed

Seeds are rarely seen in home gardens, so are not used for propagation.

Growing magnolia from cuttings

  1. Semi-hardwood leafy cuttings can be taken from summer through to autumn. These should be at least 10cm in length.

  2. Dip the cuttings in in a propagating gel.

  3. Place in pots of quality propagating mix.

  4. Keep warm and moist.

If you like this then try

Star jasmine: this striking vine can be trained to grow vertically over wires and trellising, as well as horizontally, to create carpets of bright green covered with white, star-shaped flowers.

Evergreen magnolia: stunning spring and summer flowering display with the advantages of evergreen growth.

Lilly pilly: an extremely popular native plant, with a distinctly tropical look and glossy mid-green adult leaves.

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