Friday, 15 March 2013

Please don't put a brick through my window!

“So I was using a neonicotinoid...”

In a short time I doubt I'll be saying that again! At some point in the not-too-distant future the insecticide group known as the neonicotinoid group will be banned from use in Europe. This insecticidal group of chemicals makes up about 25% of the European pesticide market, so there is a battle being waged between the producers of this chemical group (who predictably claim that the environmental effects of their products are minimal) and anyone who understands the importance of beneficial insects, including (most famously) bees. As the neonicotinoid group is a broad spectrum insecticide it will kill any insect. Although the doses and application rates are aimed at damaging populations of small insects, it also has a knock-on effect on larger insects that collect pollen and nectar from the flowers of treated plants, including causing infertility and abnormalities in bees, and subsequently population decline.

I'm not going to enter into the issues around the neonicotinoid group here. I would like to draw your attention to a product...

This is Intercept. It is a neonicotinoid that is available solely to professionals who have a pesticide handling certificate (usually a PA1/PA6). It is manufactured by Scotts, who also make slow-release fertilisers, “Miracle Grow”, and various insecticides and herbicides.

Now before you lobby to have all Scotts products removed from sale because they [currently] make neonicotinoids, I would like to draw your attention to the label. 

On the side of the label it makes it absolutely clear that this product must not be used on any edible crops, or even compost that might be reused to grow crops for human or animal consumption. Fair enough, it's poisonous and has a residual effect. Let's look at the bottom of the label....

“HIGH RISK TO BEES. Do not apply to crops in flower or to those in which bees are actively foraging. Do not apply when flowering weeds are present.”

This particular bottle of Intercept was bought in 2008 and has a clear warning that there is potential to harm bees.

How does one company know that their product is dangerous to bees warn users 
while another (Bayer) continues to maintain that neonicotinoids are not harmful?

Neonicotinoids will be banned from use. Horticulture is better placed to cope with this than agriculture; neonicotinoids have almost already been replaced by a bacterial product to combat vine weevils in compost ('Met52') (as well as using nematodes if needed later in the growing season), Integrated Pest Management (IPM), better horticultural practices, and (if necessary) the remaining chemical products available to professional growers.

At work we seldom spray any stock in the tunnels or outdoors- birds and insects do most of the work for us- and maybe the occasional isolated batch might need a chemical treatment if a pest population is getting out of hand. We never routinely 'blanket spray' plants, even though we grow an enormous range and are always short on manpower- nature takes it's course and we intervene only if absolutely necessary. Most hardy stock nurseries run along similar lines.

So before I get a brick thrown through my window... why was a using a neonicotinoid product when I know about the dangers to bees? I had a very serious root aphid infestation on the root-balls of some large Pinus roxburghii. Ordinarily plants with such bad infestations of root pests would be disposed of, but throwing away rare pines that are already more than a decade old is not an option. Am I happy with my decision? Yes. Pines are pollinated by the wind, not bees, and there is no chance of beneficial insects being harmed by the use of this product on the pine- I assessed the risks and used the product legally. Once there is an effective drench for root aphid on non-flowering plants then the little bottle of Intercept at the back of the pesticide locker will become a thing of the past. More likely we will run out of Intercept granules and then it will be banned, but at least the Pinus roxburghii are safe.

Saturday, 2 March 2013

King of Spring; the Magnolia

When it comes to splendour of spring the Magnolia is king. Large gardens in the South West boast dozens of these magnificent trees, some early collections of Magnolia species are now around 100ft tall and in March and April their blooms stand out for miles around!

Magnolia stellata
The history of the Magnolia in cultivation is almost the same as that of the other stalwarts of the 'big house' garden, the Rhododendrons and the Camellias. In the early days (19th century) if you wanted a Magnolia you would have to sponsor a plant hunter, and these brave men would travel through the wilderness of the Far East in search of Magnolia seed. Then came the wait; Magnolias take an eternity to flower from seed, often somewhere between 20 and 50 years depending on species- growing Magnolias from seed really was an investment in the future of a garden! It is not unlikely that many of the men of wealth who sent the plant hunters out to far flung corners of Asia in search of seed never saw any flowers in return for their investment.

As time has passed Magnolia growing has moved on, and now you can buy some Magnolias in your local garden centre, although visiting a specialist for something special is very much worthwhile. Selection of clones, new propagation methods and good plant breeding have made Magnolias far more accessible to the general market, although Magnolias are still not cheap- they are not easy to graft and take a lot of time to make a plant good enough for sale, so it's unlikely that you will get a good Magnolia for less than £20, and even then it will be fairly small. Price isn't all that much of an issue really; most gardens will only have room for one or two of these trees, so it's a matter of finding the right tree for your budget.

In a previous blog post I mentioned the time-scales involved in breeding Camellias and how that affects their price and makes raising new varieties unattractive to nurseries. Magnolias have the same problem, but much worse! By the time a breeder's Magnolia hybrids are flowering in a stock field 20+ years may have passed since the cross was made and the seeds were sown. Once a new variety is selected from these seedlings (and indeed if a seedling is good enough to select) material must be taken and grafted onto rootstocks to create more propagation material. This process must be repeated for many years; each grafted plant will have to be grown for several years until it is big enough to yield more material for grafting. In order to yield enough material to make enough plants for release onto the market these plants must be grown on and on... Magnolia breeding needs time, space and patience!

Gardeners benefit well from this mammoth breeding task- modern hybrids are often superb, with excellent colour, form and flowering. Some varieties are well known, like Magnolia 'Susan' with it's deep purple flowers, and M. 'Star Wars' with it's open flowers and slightly pointed petals. 
Magnolia 'Susan' in bud
Magnolia 'Star Wars'

 Some flowers are just sublime, like this M. 'Iolanthe' which has a superb scent and enormous mouthwatering flowers.
Magnolia 'Iolanthe'
Some selections are superb for creating 'flower power', such as M. x loebneri 'Merrill', a very good alternative for Magnolia stellata (top).

Magnolia x loebneri 'Merrill'

For sheer beauty M. x soulangiana 'Picture' is awesome, as are some of the yellow Magnolia hybrids, like M. 'Elizabeth'.
M. 'Picture'
M. 'Elizabeth'
If you are making an investment in a Magnolia you must be sure that you can accommodate it. Soil requirements are simple but important; a continually moist but free-draining (NEVER waterlogged) slightly acidic soil is vital. Magnolias will take plenty of sun anywhere with reliably moist soil (this is why they do so well in the west of the UK!), but will tolerate some light shade without any ill effects. Because their flowers and leaves are fairly large Magnolias are best in a spot sheltered from the wind. Also, as they are early flowering plants frost can be an issue- try to site your plant in a spot sheltered from frosts, but also choose the right variety- blooms of a white Magnolia will be visibly damaged by even a light frost, so if in doubt go for a variety with darker flowers so that only damage from hard frosts will be noticeable.

The next important requirement is space, and this is why you must choose your Magnolia carefully and if possible have a good in-depth conversation with a specialist Magnolia grower; some Magnolias have an upright habit (such as M. 'Star Wars') but others are more spreading (such as M. stellata). Make no mistake- you are buying a tree, so it's important to make sure that you have space to fit a Magnolia as well as a Magnolia suitable for the space. On the whole the yellow flowered Magnolias seem determined to make a tree with a straight leader- pruning is very much inadvisable. Your budget will also play a part in your decision... some Magnolias are easier to propagate and grow, so will be available as small plants fairly cheaply (M. stellata is a good example, and M. x loebneri 'Merrill' can be fairly inexpensive) and will flower well as young plants, but some plants are difficult to grow and are naturally more tree-like in habit, so will only be available as larger plants with a larger price tag. It is important to get the right variety- if your heart is set on a large flowered tree then you must save up!