MAGNOLIAS

By Charles Williams

“No group of trees and shrubs is more favourably known or more highly appreciated in gardens than magnolias and no group produces larger or more abundant blossoms” stated the great Chinese plant explorer, Ernest Wilson soon after the turn of the 19th Century.

The purpose of this article and its associated pictures is to try to persuade readers of the validity of this statement and to quash some of the myths about magnolias being difficult to grow.

1. Historical Background
Magnolia was named by the Swedish botanist Carl Linneaus in 1737 in honour of the French botanist Pierre Magnol (1638-1715).   The plant which Magnol had described is that we now know as Magnolia virginiana an evergreen American species which despite its name was already growing in Europe by the mid eighteenth century.

The earliest western record of magnolias in cultivation is found in Aztec history at the time of Montezuma where there are illustrations of what we now know to be the very rare Magnolia dealbata.   This plant survives only in a few places in the wild and, although climate change is largely to blame, the natives cut the flowers for festivals and this prevents the plants seeding.   It was found by a Spanish explorer called Hernandez who was commissioned by Philip II of Spain and whose work was published in 1651.

Magnolias are however one of the most primitive plants in evolutionary history and fossil records show that magnolias once existed in Europe, North America and Asia over 100 million years ago.   Today they are indigenous only in Southern China and the Southern United States.   There are about 80 species of magnolia of which roughly half are tropical.   The genus magnolia is the largest within the Magnoliacae but there are also 9 other linked genera which include Liriodendron (1 species only), Michelia (45 species) and Manglietia (25 species).
After the latest reclassification of Magnoliacae, Michelias and Manglietias are now all renamed as magnolias.   Astonishingly one of the closest genetic relations to the magnolia is the buttercup.

Some of the earliest references to magnolias in literature refer to their purported medicinal properties.   Anyone who has smelt the peculiar smell of magnolia sap – and what an alluring smell it is - will see how likely this was to appeal to those involved in medicine.    The flower buds of Magnolia salicifolia are used in Asia to treat headaches and allergies.  A 1985 study reports on the potential use of this drug in the treatment of cancer.   Another recent study found that tonics from the bark of Magnolia officinalis lessen tremor in patients with Parkinsons disease.   Who knows what may yet be discovered.

Magnolias are pollinated in the wild by primitive wingless beetles.   Beetle pollinated flowers are characterised by their large size, white or pink colour, lack of nectar and abundance of pollen.   Beetles feed on pollen and most magnolias do not have nectar although they do have scent.   Beetles existed many millions of years before winged insects and hence their primeval appearance.   In our climate most spring flowering magnolias flower long before many insects have appeared in early summer and hence why many species seldom, if ever, set seed.   In parts of China this leads to an interesting spectacle where stands of Magnolia campbellii are predominantly white.   In Europe where beetles do not exist and wind or insect pollination is a reality Magnolia campbellii is predominantly pink.  In the wild Wilson and Forrest record the natives burning the white flowered trees as firewood.   In the West we treasure the white campbellii as being unique.   This may have as much to do with genetics as beetles but it does show what primitive and unique plants magnolias are.

2. What is a National Collection and what is the point of a National Collection?
Well over half the magnolia species in existence in the wild are classified as being endangered and on the United Nations ‘Red List’.   The purpose of a National Collection is to establish in one place as many species and cultivars of magnolias as possible to enable the public to see and assess them together.  The holder of the National Collection is responsible for ensuring the survival of the genetic store of such plants so that it is available for future hybridisation or genetic work or indeed for returning to the wild.    In the case of magnolias one simply cannot go to Yunnan or Schezewan in China.   Even if the magnolia species which Wilson and Forrest collected from around 100 years ago have been burnt as firewood, ring barked by goats or cleared for agriculture, we will still have pure genetic plant material originating from the wild of many of these species at Caerhays.   In quite a few instances Caerhays still has the original and oldest plants of particular species in the Western world.

Caerhays is not the only holder of a national collection and there are great strengths in this.   When climatic disasters strike there are others with similar collections to ensure that a species or cultivar is not lost. Bodnant and Windsor Great Park also hold national magnolia collections.   The benchmark is that one must have over 75% of the species and cultivars listed in Hilliers Catalogue.   At the last count there were nearly 350 of these.

3. Cultivation of Magnolias 
Magnolias are easy to grow and relatively pest free.   Once established they need the minimum of attention.

a) The perceived problems of size, first flowering and frost damage – Magnolia myths.
The three things which most frighten people about magnolias is firstly their ultimate height as tall trees, secondly the length of time which they take to produce their first flowers and finally the susceptibility of the early flowers to frost.
Although the 80-100 feet tall Magnolia campbellii, sargentiana robusta and mollicomatas which produce such a spectacle in February and March in Cornish woodland gardens can appear a bit daunting it must be remembered that magnolias grow much taller in Cornwall than they will in other parts of the country where rainfall is much less.   There are several species which are smallish shrubs and which are entirely suitable for smaller gardens or even tub growing (e.g. Magnolia stellata, M. lilliflora Nigra and several crosses between these two species - ‘Susan’, ‘Randy’, ‘Ricky’ and ‘Jane’).   Most varieties of Magnolia soulangeana are excellent garden plants which will become large shrubs but can readily be pruned.   Not all magnolia species and varieties are therefore just the preserve of large country gardens although tree magnolias should clearly not be grown too near houses.

If you grow tree magnolias from seed they may well take 10-15 years until they first flower.  In one instance at Caerhays a magnolia took over 40 years to flower.   However, most magnolias sold today are GRAFTED plants. This means that the long wait until first flowering can be readily avoided because of scion material used to make the graft comes from the flowering tips and branches of existing plants.   Some grafted tree magnolias will even flower while still in their pots but it would be very bad luck for a grafted plant not to be flowering away within 3-5 years from planting.   This criticism of magnolias is also therefore a misconception.

Clearly any plant which comes into flower in February or March runs a very real risk of having its flowers frosted.   Even in the mild Cornish climate this can and will happen some years.   However magnolias adapt to the climate of their surroundings and a Magnolia campbellii in Yorkshire might only come into flower in April in a cold spring.  Certainly it might well still get frosted but it is not necessarily going to happen very often.

If you live in a frost pocket or in the North of England or Scotland you need to select magnolias which do not flower until mid April and mid May.   There are plenty of taller growing magnolias to choose from and ‘Serene’,  ‘Iolanthe’, ‘Caerhays Surprise’, ‘Atlas’ or ‘Apollo’ are all good choices.   Additionally most Magnolia Soulangeana hybrids do not come out until May.

So select the variety for your area and stop worrying too much.   If our current run of very mild winters continues the risk of frost damage is minimal and magnolia flower buds are very well protected by two furry outer coatings which only drop as the bud opens.

Just because the flowers can occasionally get caught by frost does not mean that magnolia trees and shrubs are not totally hardy.   They most definitely are so put these three popular myths behind you and treat them as the uninformed misconceptions that they are.

b) Soil conditions     
Magnolias perform best in a loamy, well drained soil but rich in organic matter.   You can make an easy contribution to the organic bit by putting plenty of compost or well rooted manure into the planting pit and keeping the plant regularly mulched.   Magnolias are surface rooting plants which respond well to mulching.

A slightly acidic soil is best.   Lime or alkaline soils are more difficult for magnolias but, while nothing will grow on pure chalk, many Magnolia stellata and Magnolia soulangeana varieties grow perfectly well on ph’s of 7 as opposed to the optimum 5.5 – 6.5.   If you look at the magnolia collection in Windsor Great Park and in the Savill Gardens it is hardly an acidic soil area but with the application of peat and fertiliser you would not know it.

c) Location
Magnolias prefer to be grown in full sun but will tolerate dappled shade providing there is plenty of room for them to grow and expand without becoming misshapen and ‘leggy’.   If magnolias are squashed or competing for light and space with other trees and shrubs they will not flower well.

Although, as explained, magnolia trees and shrubs are totally hardy it is foolish to plant them in windy or exposed areas where not just the flowers but also their large leaves can get damaged unnecessarily.   Magnolias hold their leaves long into autumn which accounts for their phenomenal growth rates. However it makes the trees vulnerable to heavily leafed branches literally splitting off or breaking in strong winds.   Some shelter is therefore advisable.

If you live at the bottom of a hill or a deep valley try to avoid planting your magnolia in the very bottom of a frost pocket.  Cold air and frost moves downhill and concentrates in valley bottoms so try to plant uphill if you can.

d) Pests and Diseases
Magnolias are relatively pest and disease free in comparison to say rhododendrons.   However, as usual in nature, there are a few things you can do to avoid disasters.   The majority of magnolia casualties soon after planting can be attributed to one of the following problems:-

i) When you plant a grafted magnolia the old soil level in the pot must marry up and be level with the soil level in the ground.   If you bury the root ball or pot full more deeply you will very probably end up covering the graft with soil.   This will soon cause the graft to become infected and the plant will die even if the root ball survives.  You can easily achieve the same result by mulching too thickly and again covering up the graft.  For more tips on how to plant trees and how to treat grafted plants please refer to the Planting Advice Section of our main website.

ii) Very often we are told that a customer’s magnolia has come into leaf and then suddenly the leaves have vanished or gone brown or have turned into leaf skeletons.   This is the work of small slugs which live in the soil and only emerge in damp weather usually overnight to take their fill of young magnolia shoots and leaves.   Snails may help out too but you seldom actually see them at work.   Prevention is possible but in extreme cases there is no cure after the event.   In April and May as the leaves unfurl you should add slug bait to the base of the plant and repeat this after rain for a couple of weeks until the leaves are fully formed.   After 2 or 3 years of growth the plants can usually withstand a slug attack but not before their root systems have formed properly.

iii) The sap in magnolia stems and bark is highly pungent and therefore especially attractive to rabbits.    If you planted out 10 trees only on of which was a magnolia, it is a near certainty that the magnolia will get ring barked by rabbits first.   You may say that you do not have a rabbit problem but it only takes one!   The solution is to put a spiral guard around the main stem but some magnolias have lots of side shoots which makes this difficult.   Better still is to make up a circle of 1 inch wire netting which is at least 2 1/2 feet tall and surround the plant with this.   This will afford genuine rabbit protection.   Happily deer do not seem to like magnolias as much as rabbits at least with us.

4. Hybridisation of Magnolias  
  
Making your own unique cross.

Anyone can hybridise two different magnolia varieties when they are in flower to create a new hybrid (or rather lots of new hybrids) of your own.

Cut and take a flower from one magnolia plant, the ‘Pollen Parent’ and spread the pollen exuding from its stamens onto the stigma (or female reproductive part) of the ‘Seed Parent’ flower on the other magnolia plant.

Then remove all the tepals (petals to you and me!) from the ‘Seed Parent’ flower as well as the male pollen bearing stamens.   This should ensure that the ‘Seed Parent’ will not get visited by other winged insects carrying other different pollen as, without the petals, there is nothing to attract them.  It will also avoid self fertilisation whereby the flower fertilises itself with its own pollen.

You then clearly mark the twig on which your cross has taken place and hope that the stigma will grow and develop into a seed pod with viable seeds which represent your unique cross.   If it does, and there is no guarantee at all that it will, then the seed can be collected in October or November when the seed pod splits and the bright orange individual seeds can easily be seen.

How to grow these magnolia seeds is described later in this article.

We have already discovered the number of magnolia species which exist in temperate (as opposed to tropical) climates of China and North America.   There are 600 species of rhododendron but only about 80 magnolias.   Therefore the number of possible crosses between species is much more restricted.

In the UK climate not that many magnolias do actually set seed so the hybridiser is again restricted in his choice of subject.   In addition evergreen magnolias will not cross with deciduous ones and pollen from magnolias which flower in the spring can hardly be used on summer flowering varieties (at least by amateurs).

All these problems mean that there are perhaps only 1200 – 1500 properly registered and recorded varieties of magnolia hybrid worldwide.

We have explained why pink is the genetically dominant colour in the majority of tree magnolias.   This is even more true when breeding.

For every thousand magnolia seedlings which grow on to become flowering plants perhaps only one will be sufficiently different in terms of colour, habit or flowering time/period to enable it to be worthy of formal registration by the Royal Horticultural Society and the International Magnolia Society.   The remainder may be very nice plants or even extremely lovely plants but they will not be sufficiently different to be worthy of a name and registration.

Naturally people who make deliberate magnolia crosses and try hard to produce something new and different are very much more likely to find success than the keen gardener who simply grows lots of random seedlings which he has collected. However genetics can throw up random surprises but very very seldom indeed.

What has happened is that scores, if not hundreds, of magnolias have been named by people who very much like them in their own gardens.   We have Magnolia campbellii  Lamellyn, Sidbury, Wakehurst, Lanhydroch  - to mention but a few well known gardens.   They are good, even great plants, but are they sufficiently different to be worthy of a separate name?   Perhaps or perhaps not?

Then you get the experienced breeder who produces lots of seedlings (all different of course) from his deliberate crosses.   Instead of waiting to see how they perform individually over several years and selecting the very best only for naming, the breeder gets carried away and names/registers far too many.   We end up with lots of magnolias which are very similar indeed and the public get confused.   They want to buy excellence but do not know how to find it.

If you look at the labels on the magnolia plants at Caerhays some will just say M. mollicomata x M. ‘Lanarth’.   This means that the plant was a deliberate cross rather than a chance seedling.  (If it was a chance seedling it would say x unknown for the ‘Pollen Parent’).    Effectively this means here is a possibly quite decent Caerhays bred hybrid which sadly is not good enough for formal naming and registration. 

Since we all accept that most magnolia seedlings take at least ten years to flower the process of hybridisation in magnolias is very slow indeed and, in a lifetime, there are few chances to improve on your earlier mistakes.

And that is not the end of the story either.   If a plant does get named and registered it has to be exceptionally good if it is to achieve commercial success and be grown and propagated by nurseries.

5. Caerhays Bred and Raised Hybrids

In keeping with the strongly held beliefs outlined above Caerhays has named only half a dozen new magnolias in the last 50 years.

 Painting of Caerhays Hybrids by Michelle Bennett Oates

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