Friday, 20 May 2016

Hard and Soft Growth

The soft new leaves are normally damaged by frost and dry wind
My post is a bit of a ramble today with few actual facts, some speculation and more questions than answers. I cannot actually tell you what hard growth really is in plant physiological terms but it seems to be a phenomenon that most gardeners recognise. I don’t know whether it is a bad thing or a good one!
I was first introduced to the concept by Alec Fox, my old garden foreman when I joined Hartlepool’s Brinkburn nursery to gain my precollege experience. He was an old fashioned son of the soil and from a long tradition of private service and gardening methods going back to Victorian times. I would like to add that the Victorians were better gardeners than we are although their techniques were geared to more primitive technologies and lack of modern materials.
The new fangled peat based composts had just appeared on the scene. In contrast to the established John Innes soil based composts which in those days a gardener would firmly tamp down (yuk) in a pot or a tray, peat composts were used at a ‘natural density’ where compost was allowed to settle with no more than a tap or a shake. The plants in the looser un-firmed peat compost grew more quickly and softer. No doubt nutrients were more readily absorbed and arguably the plants were more luxuriant and healthy.
According to Alec they were less sturdy and more prone to pest and disease.

I was tempted to buy two soft tunnel-grown aubretia on the market this Spring. It was immediately potted into a larger pot and given a week  in my unheated greenhouse - next to the open door

Now going over it has given us six week of colour outside our conservatory. Had I put the new soft plant outside immediately it would be dead!
Bedding plants
I think gardeners these days gardeners are familiar with soft growth when they buy their Summer bedding plants from a garden centre. The old fashioned concept of ‘hardening off’ seems to have been thrown out of the window! Plants propagated in warm humid tunnels don’t have the toughness to go straight out into the cold! Sudden low temperature and worse, in my opinion, cold drying wind severely check growth or even kill. 
A gardener’s solution to modern professional omission is to try and harden the tender plants themselves. Apart from not buying and planting too early there are several alternative actions a gardener can take.
  1. Retaining the plant in its container for several days and placing outside in a protected position perhaps by a warm wall. If wind or frost is forecast place the plants inside a garage or shed for the night.
  2. In complete contrast if there does happen to be a brief opportunity in a short mild spell get the plants straight into the ground. If your calculations go awry cover them with newspaper, plastic or fleece.
  3. If you have an unheated glasshouse or cold frame use it and its ventilators to gradually  acclimatise your new plants. Even so on a very cold night throw some cover over them!
  4. Be aware that slugs and snails love soft distressed plants.
  5. The amateur gardening press excessively simplifies and lumps together bedding plants  when it advises gardeners when to carry out their planting. Such as sweet peas and antirrhinums can safely be planted in the garden more than two months earlier than begonias. Provided they are well hardened.
Nursery practices
When I have young woody plants I have raised from seeds or cuttings they grow very slowly. It can take years to reach an acceptable size for planting. If my living depended on them I would starve. Growers have learned how to make their plants grow faster. Sometimes this is by highly skilled and subtle ways working with nature and learning an understanding of plant physiology.
More often they achieve quick results by providing protection from cold and wind, using artificial heat wisely and generous feeding. Plants will often respond hugely to extra nutrition providing it is very well timed. 
When I was a young teacher the research stations talked about achieving maximal optimum growth. No longer a fashionable term - it is too honest - it’s what good successful growers do. Their use of plastic tunnels has provided a revolution in production. Hardy plants are grown inside for all or most of the year. Plants will sometimes come out of a micro-propagation laboratory and be rapidly grown on.

By any definition these plants are soft! Indeed as a result of soft and forcing growing conditions where pest and disease thrive some growers use pesticides in a preventative way. I am grateful for this when these days I am less likely to be buying in whitefly and red spider mite. 
I am less impressed when the prophylactic systemic fungicide runs out and my newly purchased Dicentra ‘Luxuriant’ dies yet again! In contrast I am delighted when a returnee garden visitor who bought one of my own plants that I had more or less chucked into a pot reports that it is really thriving in her garden.

Dicentra spectabilis new growth is very soft and is susceptible to dry wind and sharp frost.  

My coincidence I read today in ‘The Hardy Plant’  wonderful nurseryman Bob Brown advising his readers to buy Trachycarpus fortunei, the Chusan palm that had been grown ‘hard’ and was not displaying stretched long internodes. I thought he was a bit hard describing some plants as etiolated Italian imports! 
What about the Dutch? When I see large lanky Daphne mezereum at the garden centre I shudder.

It might take me five years to achieve a large plant  - but it won’t be soft!
Mike’s tale
I asked botanist friend Mike Ashford whether the terms ‘hard’ and ‘soft’ meant anything to him. He immediately told me a story. It does not necessarily draw a morale that I might wish to pursue but I will repeat it anyway!
We grew half an acre of commercial tomatoes variety Minicraigella at our horticultural college. Our holy grail was to achieve a yield of  a hundred tons per acre. We always failed. Today two hundred tons is routine in the trade. (Perhaps our efforts were not helped once when  a student de-leafing removed a whole row of flower trusses!)
Even with a variety with tasty Ailsa Craig genes our tomatoes were round, red, uniform and pappy. Just like modern ones. Not a surprise when the sugars, acids, nutrients and vitamins have to go so far round.
Our foreman David Coe would sell surplus tomato plants to his friend who had his own small holding. His mate was not a good grower. His watering and feeding were somewhat erratic and his unsterilised soil was riddled with pest and disease. His tomatoes were ‘hard’ and low yielding. They were absolutely delicious!

Tomatoes can be grown a little harder by being a little more sparing with the copious water that they need. When the sweeter cherry tomatoes were introduced to the market growers were advised to use a ‘drier regime’ . This had some success and they started to build a reputation.
Unfortunately high yield was a sweeter cherry for some growers....

My own tomatoes are delicious. You might draw your own conclusions....

My sugar snap peas grow softer in the greenhouse but they are sweet, disease free and early. That's not to mention the pretty cut edges eaten by the pea weevil!
I will be blogging about my charcoal composts at the end of the summer. My tomato growth is healthy but perhaps a little harder than usual

Home grown tomatoes always taste good
Still in the realm of vague and perhaps disconnected science, scientist friend Peter Williams reminded me of the imprecise notion of ‘ripening wood’. Woody plant growth undergoes transition from soft young shoots to hardwood at the end of the season as lignification proceeds. 
Tongue in cheek he declared he could not tell the difference between soft cuttings, semi ripe cuttings and hardwood ones. The serious point he was makings is that amateurs worry too much about definitions and precision. For him although his methods of taking and management of cuttings will vary with season it is merely a seamless progression!

If you want to read further about how I grow tomatoes, my interest in charcoal or my dicentras use the links in the right hand column. If you want to enjoy the excellent magazine 'The Hardy Plant' written by real gardeners rather than journalists you can join the Hardy Plant Society here.

Saturday, 14 May 2016

Pictures of dicentras

The genuine Dutchman’s Breeches, Dicentra cucullaria  flowered in early April
Last week a photographer came to take pictures of my National Dicentra Collection for a glossy magazine. They will be published at dicentra time next year.
Unfortunately different dicentras flower at different times and professional photographer Neil had only one visit. At least he was lucky in that several cultivars of the most popular species of Dicentra formosa were in their prime. Even so, the various varieties of this Dicentra formosa mature in a staggered sequence.
Neil had his work cut out as conditions for photography were poor. The sun shone brightly and the wind was strong!

Neil does not know I sneaked a picture of him at work

My advantage is that I am there all the time! To wet your appetite I am taking the liberty to post some of my new pictures taken this year. Where I know what they are I have given their name! I keep nice seedling variations of Dicentra formosa and some remain anonymous!
They sometimes have to fight it out 
One of the golden forms. To me it looks like permanent chlorosis
'Adrian Bloom’ one of the best reds
Some call it ‘Pearl Drops’ some call it ‘Langtrees’. It has an excellent constitution and has a long season
This was given to me with no name by famous Yorkshire gardener Nancy Boydell and that’s what I call it.
Neil came when Dicentra peregrina was in its prime
It has magnificent foliage
Another strange mixture 
Dicentra canadensis is known as squirrel corn
Dicentra cucullaria ‘Pink Punk’ starts into flower
'Stuart Boothman' has very nice foliage
My personal favourite. I brazenly call my own seedling ‘Roger’s Pink’ although salmon sometimes seems more appropriate
‘Bacchanal’ generally acclaimed as the best red
I pulled this seedling out of a mixed up clump last month
 Now where did I take this picture – I might then know its name

You can tell I am besotted with dicentra with nine previous posts. To some extent my blog is my own personal dicentra record as I have no other.
You can find more kinds and cultural information by clicking the links

This takes you direct to my first six articles
And this to my more recent three

You can do a more refined search by using the search boxes. The box at the top takes you direct to most relevant articles. If you scroll right to the bottom of the blog roll the search box gives a more detailed prioritized list of every mention.

For example if you insert ‘spectabilis’ in either box you will find Dicentra spectabilis

Wednesday, 11 May 2016

Establishing cut leaf maples and the problem of acer dieback

Overcome these two problems and they are very easy to grow

For years I failed to get Japanese Maples started and believed they needed shelter and shade. I am now more successful in getting them established and once they get going they withstand more wind and enjoy more light than I had previously thought.

Getting cut leaf maples going
My usual scenario was new young plants in the ground making new leaves in Spring and looking really healthy until hit by a couple of days of a cold drying Spring wind. The leaves would shrivel and die. The plant later failed to make new leaf growth and perished.

If you see young cut leaf maple leaves starting to show shrivelling leaves in dehydrating conditions you need to ensure the roots are not dry - but beware, the more likely explanation is that the ground is too wet and the rate of water uptake cannot manage to replace the water loss by transpiration. If you have a young plant still in its pot there may be time to bring it under shelter and for a plant in the ground to temporarily protect it. But it’s probably too late!

It seems to me there is a problem of a young plant getting its root system and its top into some kind of balance. As an example a purchased plant might have a large top which is out of balance with a smaller root system. More likely the roots of young maples have been slow to extend their roots when planted into the ground. If drainage is at all suspect, even for a very short period root growth is poor. Roots might even die. Young cut leaf maples hate cold wet waterlogged soil. So do established plants but once they get going are very much more tolerant.

Tray of Peter’s seedlings
Peter Williams is my expert.  Every year he raises young seedlings in his tunnel and also propagates named varieties by grafting. His advise on successful planting is to plant a larger plant already very well established in a large pot. If you have an unheated greenhouse it will be better for your new plant to spend its first Winter inside. If you choose to enjoy the lovely cut leaf foliage plant as a pot specimen outside in the garden for a year or two all the better; it can be brought inside for at least another Winter. Potted plants left standing outside in a wet Winter, even in well drained compost can be too wet - and maples are very sensitive.
When you eventually plant your larger plant out into a permanent position do so in Spring and remember in the first season when you run into dry weather to give it some water!
(I qualify this advice in my pictures when some of my own very large tub display plants have of necessity been transferred to the ground. With their very large and mature root resource they were planted in Autumn)
Several years ago Peter gave me six very healthy two year old cut leaf maples which I immediately planted after hardening off in Spring. The rabbits immediately ate two of them, one got trodden on, one died of drought under a tree. Two struggled on and were checked and torn by the wind before the rabbits came back. Be warned.
On the other hand I have ten very healthy large specimens thriving in diverse conditions in my garden.

Shoot tip dieback

The problem 
This is a less serious - but a very common - problem and usually occurs on more mature established plants. This is not usually dieback of complete branches  - that is something different, sometimes when plants have been grown too soft in a nursery. Also distinct is the complete death that eventually comes to snake bark maples which refuse to survive on my soil.
It is more of a cosmetic irritation when shoot tips die. Usually no more  than a few inches. Unusually one of my plants where I had failed to give it earlier attention had this Winter brittle dead tips of up to six inches long.
I am pretty certain this dieback is caused by an infectious disease which might be fungal or bacterial - I really don’t know. When I had my own clients I used to find it all over Yorkshire. 
The cure is very simple, just cut dead ends away. If you fail to do so for several years you might find you have a real problem. You can prune it out any time you see it, Summer or Winter. I use my secateurs either on individual shoots or more often in little bundles. You can even rub out brittle tips with your fingers, it’s very relaxing!

You can be quite ruthless
Peter observed that acer dieback has been particularly bad this year as a result of our wet Winter. I remember it was always worse in clients' garden when their plants were in heavy shade. It is a disease caused by high humidity and failure to prune out dead wood.

Photo-stories of my own cut leaf maples

The dead wood is very brittle and can be easily rubbed away 
I was a bit over cautious overwintering this tub plant in my cold greenhouse this Winter. I feared excessive Winter wet. It has now been potted into a larger pot to take the place of a larger plant now transferred to the ground
Some cut leaf maples are more vigorous. This was bought as a ‘standard’ garden centre tree and immediately planted outside when dormant
Apart from beautiful summer foliage maples have fine Autumn colour
This is the same plant as the above picture. I complacently thought it did not have dieback… but look carefully!
 This was kept in a tub for several years and I transferred it to the ground last Autumn...
(two year old picture)
…and it is doing very well this Spring, but I have remembered to thoroughly water it in this present dry spell...
...the same plant showing Autumn colour a few days before I planted it in the border last October
This plant was a tall soft grown plant from B&Q! After a year or two of standing still and considerable dieback it has made a fine plant of character
I am particularly fond of it…
…as you can see!
In full sun in a very windy part of my garden the young leaves are never wind damaged
My reasons for fearing excessive winter wetness outside in small and therefore shallow pots in very wet spells is the not generally recognised phenomena that shallow soil profiles hold a lot of water against gravity which can lead to poor aeration and root death. I explain the principles in this fun post It is the reason why my small acer was placed in the greenhouse where I have control of the watering.

Tuesday, 3 May 2016

The significance of the decline in world bee populations and why do our pears sometimes lack seeds?

There is a fashionable meme that if we lose our bees we will all starve. This is complete nonsense. Don’t get me wrong, I don’t deny that  bee populations are threatened and that bees are magnificent creatures who play a fundamental role in the pollination of many crops and flowers and that we must do everything possible to preserve them.

My story today starts when my friend Peter somewhat disingenuously wrote to a supermarket chain and mentioned that he had noticed that their magnificent pears seemed to lack seed.

The reply would do credit to a moonlighting Lyra Silvertongue. The reply is 100% correct and a masterpiece in product promotion

Thank you for sharing your observation.
Our commercial British apples and pear growers all aim to produce apples and pears with good seed set.
This is because;
1) As seeds develop with the fruits they naturally release hormones which will promote the growth of flesh and result in larger fruit size (and therefore positively impact on crop yield).
2) Fruits with evenly set seeds are more likely to meet the Horticultural Marketing standard for Class I quality and therefore get higher return i.e less misshapen fruit.
3) Fruits with evenly set seeds typically store better.

For this reason  a significant number of our growers introduce bees (honey bees and solitary bees) to their orchards and preserve species biodiversity in wind breaks to provide habitat for over wintering insects which play a role in pollinating their crops in the spring.

Many of our growers are also involved in research projects with East Malling Research, (improving pollination in pear orchards), Southampton University (improving habitat around periphery of apple orchard to improve pollination) and Reading University. (improving ecosystem services within apple orchards)

There are a couple of reasons for reduced numbers or absence of seeds depending on variety and all linked to poor conditions at pollination - e.g extreme temperatures which abort pollen tube growth and development inhibiting the pollen from fertilising the ovary and forming the seed or low temperatures which reduce insect activity.

The Royal Gala variety which you specifically mention is a particularly precocious variety and even in years when conditions for pollination are poor it still tends to set a large number of apples and it is usual for the flesh of Gala to continue to grow following a poor pollination period without the presence of seeds (known as parthenocarpic development) - hence the reason for lack of seeds in this variety.
It is possible that in years when weather conditions are poor, (cold and wet, growers sometimes apply naturally produced hormone ‘gibberellin’ to  improve skin finish on apple and pear varieties prone to rough russet e.g Conference pears and Cox .  These gibberellins' are safe and legal and under certain weather conditions can stimulate the development of parthenocarpic fruit (virgin fruit) which could also explain an absence of seeds in varieties such as Cox.

This is a very helpful letter and I think its technical content is very interesting. The sting in the tail is in the last paragraph. I do not wish to condemn this technical innovation, I personally think the use of gibberellin is something to celebrate as I will discuss in a moment.

 A really lovely Cox that Peter bought at his local supermarket

Only one seed!

A full set of seed

Core blimey

Why the threat to world food production by the loss of bees is relatively small.

Not all bees are declining, far more other organisms sustain pollination than assumed and most of world crops are wind pollinated and do not require animal pollination at all. Nor must we overlook new innovations that might aid pollination

Taking the last point first! In excess of 80% percent of the world’s food production is from wind pollinated crops or those that do not require pollination. 

Wind pollinated grasses dominate world crop production albeit not this ornamental plant

It is truly amazing and not a little disturbing that almost 90% of the world’s nutrition comes from a basket of five.
The annual production of these five crops - in ballpark figures - are
Maize 900 million tons
Rice 750 million tons
Wheat 700 million tons 
Potatoes 400 million tons
Cassava 250 million tons

(Its a little confusing when you check out such figures. For example sugar cane comes in at a whopping 2 billion tons. More relevant is the amount of refined sugar - about 175 million tons. My figures today are much rounded and will vary with how yields are expressed in the literature e.g if expressed in monetary value they give no indication of quantity)

Potatoes are vegetatively propagated from stem tubers (and alarmingly some consider them threatened by virulent new natural sexual strains of potato blight).
Sugar cane is propagated by division and so are bananas. Bananas are interesting because from ancient times they have been selected to be seedless. With no seedling variation they are threatened by the scourge of Panama disease. Not all crops are secure but my argument today is about crop loss caused by the absence of bees.

For many crops the edible part does not need pollination. This does not mean that bees are not needed for seedsmen to produce seed.

Worldwide there are 20,000 species of bee - although only 2% of these do most of the bee pollination. There are real fears about honeybees and there appears to be a perfect storm of pest and disease, habitat loss, agricultural mono-cropping, pollution and spraying of pesticides such as neonicotinoids. Loss of hives frequently seems to be some kind of sickening symbiosis.
Sturdier bumble bees sometimes are more significant pollinators than honey bees. They are in decline too.

Its not all gloom and doom. Worldwide research investigates how to overcome bee problems and if solutions are found nature has a great capacity to bounce back.

Although bees have no significant role in pollinating wind pollinated crops, their pollen can be a source of nutrition for bees

Not only do the less common bees contribute to crop pollination, so do a myriad of other unheralded insects, mites and spiders - and so many more. Their contribution is often overlooked when worrying about bees

Ant on blackthorn

Ant on dandelion
Butterfly on sedum
Gibberellins and other technical solutions to the absence of bee pollination
I think we can almost discount hand pollination although this is important in private gardens and a few specialist labour intensive crops. Potentially plant breeders might bring us more seedless fruits such as grapes.  More self pollinated fruits can be bred. There is scope for innovative introductions of pollinating insects in protected environments.

Gibberellins are already used worldwide where pollination is difficult. As Peter’s letter points out it is a perfectly natural and harmless material sprayed onto the flowers. It is a natural plant hormone which is fundamental to many natural plant growth processes such as controlling seed dormancy and fruit development.
A huge range of crops already benefit from growers’ use of gibberellin, not least apples and pears. A quick search of the net shows it to be often used on blueberries, melons, grapefruit, oranges  tomatoes and grapes - and that is just scratching the surface.

Bumble bee on my own stonecrop. Every little helps

Preserving the bees
Although the thrust of this article suggests we would survive without bees it is almost unthinkable that we should need to do so. 
There are many popular articles that show how gardeners can help with bee conservation and I have previously posted my own.

Some of the bees flitting in my own bonnet are....
Recognising the value of bee friendly plants wherever they come from.
Not insisting that planting schemes in wild places only use native plants. We need plants of the world and their hybrids if we are best to preserve natural environments.
More purposeful planting of pollinator friendly plants on agricultural fringes and not giving grants satisfied by only growing a few weeds.
Recognition of trees and shrubs as copious sources of nectar and their diverse planting in farming areas to ensure continuity of season
More locally focussed measures in fruit growing areas.

The bees knees
Thank you Peter and Cathi for the pictures

This link takes you to my previous four articles on bees
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