Thursday, 28 February 2013

Our slimy friends



Slugs and snails
When visiting parties used to come to Bolton Percy cemetery I was often asked why my hostas were not damaged by slugs! Funny, when gardeners get together they always talk about slugs. It must be a measure of slugs’ success in eating our plants!  The observation about my plants was scarcely true, but did reflect that my hostas were healthier than  those in normal gardens. According to gardening lore, garden hygiene such as avoiding plant debris reduces slugs. With my methods of directly recycling fresh organic matter what’s going on? I have argued for years, perhaps tongue in cheek, that it did not matter a damn if I encouraged more slugs, as long as they were doing what nature intended, eating decaying organic matter which they prefer. Indeed it’s part of the natural cycle of decay. Slugs have an image problem.They need to employ Bartle, Bogle and Hegarty, we would soon be singing their praises. “Put it this way”, I say in my lectures, “no wonder the slugs eat your hostas, if you clear away all garden debris there is nothing else for them to eat!”
There is  some scientific support for this idea. First I must explain, that there are hundreds of different slugs and snails. What is true of one may not apply to another. In this post for convenience I write ‘slugs’ when I mean both slugs and snails. Years ago, I read an interesting article in the ‘New Scientist’ about slug slime trails. These are super-highways for slugs which they continually re-use as they zoom around our gardens. I found it very interesting to read that the more slime trails they crossed, the less fecund they become. It’s a natural way of controlling their own population. If true, it’s rather ironic, that all those gardeners -  often eccentric academics - who go out at night with a torch, ‘picking slugs’ merely succeed in making them breed faster!  


A lady recently did an interesting piece of valid research that if you pick up a snail and fling  it away, unerringly it will find it’s way home!
Fancy a drink at the Slug and Pebble?



Slug biology
They are the only land living mollusc. I love the word gastropod, the name of the group to which they belong!  An interesting feature is their rasping tongue called a radula. It’s a kind of ribbon with thousands of replaceable backward pointing teeth (I don’t mean dentures!) Like sandpaper it scours the plant leaf to produce the damage illustrated above. Slugs are hermaphrodite and have a very interesting sex life, but I will not go there! 



Water snails

Using  slug pellets
I despair when I see blue mulches of slug pellets. I break out laughing when I see  ‘protective circles’ of pellets around plants. Don’t the blue mulch brigade realise that pellets are a poisoned bran bait and that such large quantities are a danger to domestic pets and wildlife! Pellets only need to be used in miserly amounts, half a dozen pellets a square meter will usually do the job. For my acre garden, a standard tube of pellets lasts me about three years - and most of these are used in my greenhouse!  As to the protective barrier idea, the bait brings the slugs right up to your plants where they may very well decide that your plant is rather tasty! Pellets should be scattered a short distance away from your vulnerable newly planted brassicas.
There is an important issue as to whether slug pellets are safe to wildlife. If used sparingly in the domestic garden, I believe that they are safe, although I cannot vouch for their widespread use in agriculture. Best to apply the pellets under a canopy of plants. It is suggested dead slugs might be eaten by birds but this is disputed. Pellets really are dangerous in packets accessible to cats and dogs. There have been tragedies where pets have eaten poisoned bran direct from the pack. I am told that these days, bran is treated with animal deterrent. 

The most vulnerable plants to slugs are those that are newly planted. Perhaps that’s because they are soft from a previous propagation environment or as many gardeners believe, slugs ‘smell the stress in a wilted plant’. After all, as stated previously, their preferred food is dead plant tissue. On the rare occasions I use pellets outside, I apply in the evening before I am due to plant. Try and use pellets where and when they will remain dry. Wet soggy pellets are of little interest to slugs and the metaldehyde poison becomes completely ineffective.

There are  a legion of methods of slug control. Most are fiddly or ineffective and may not be wildlife friendly. For example ‘slug pubs’ are likely to kill desirable ground beetles. I would be very interested to hear of your own successful methods. I understand that wildlife friendly slug pellets are now being marketed. But read these doubts. In 95% of my garden and in all of my natural gardens I use no slug control at all. 


Sometimes checking out facts in google I come across something interesting. The story in wikipedia under the heading ‘famine food’ appealed to me!


Monday, 25 February 2013

Mainly narcissus and daffodils

Remember the warm spell at the beginning of January!


I am lumping them together, they are all narcissus, daffodils are the ones with the large trumpets. I love them all, but perhaps daffodils most. So popular, that some people suggest they may be over-planted. I once read that a particular variety, I forget which one, made up the greatest total mass of vegetatively propagated identical genetic tissue in the world! This is probably wrong!
Apart from their bold beauty, I adore narcissus because they hold their flowers a long time, there is a huge range of varieties and species, and by planting a sequence of early and late varieties you can enjoy flowers for up to five months.

Narcissus are  wonderful for naturalising. Planted in the ground they become stronger each passing year and thrive in a huge range of soils. A man on the television recently said they are intolerant of poor drainage. Had he never seen the beautiful drifts of daffodils in Farndale, North Yorkshire.There, they are frequently flooded, and grow right to the water’s edge. I often see snowdrops in wet conditions too, never hyacinths and tulips.

A little worse for wear these daffodils have been under water for a month.

Follow my narcissus this year
I am intending, in this blog, to follow my own daffodils as they progress throughout this coming year. Other than those in tubs they are all permanently planted. 

In beds and borders
The snowdrops were there first!

Provided you don’t dig, narcissus can stay in place for years. It is best to plant new bulbs before the end of September - unlike tulips when if necessary, you can wait until Christmas! I try a few new varieties each year.There is an enticing range and they are not all yellow! I plant mine in discrete clumps where they have room to die down in sunshine before being overgrown by summer vegetation. Be aware that the changing landscape of a garden such as the growth of shrubs and trees may eventually heavily shade bulbs. When this happens either prune the bushes or transplant the bulbs. Do not be afraid to move them ‘in the green’, otherwise you might forget their location! Shaded bulbs ‘go to grass’ and will not flower. But read on, do not throw them away! 
In tubs and planters outside.
I make up a few new tubs each year, others I refurbish and some I do not disturb at all. Eventually with the ravages of time, animals and neglect they subside and any surviving bulbs can be convalesced to permanent planting in the ground.
Because it is sandy, I can use my soil instead of compost in tubs. I prepare soil with slow-release fertilizer, dolomitic limestone (it’s my choice of lime) and very judicious use of NPK compound fertilizer. More cautious gardeners might use John Innes No.2 compost instead. My new bulbs often come from Parkers Wholesale and all my Spring bulbs are planted by the end of September. They remain in my ‘nursery’ alongside my greenhouse, until they burst into growth and are ready to display. 
Established tubs are given a top dressing of my Yara Mila compound fertilizer in August and January. Growmore is a suitable alternative. (I do not use any fertilizers on my bulbs in the ground).
An important cultural note. In the winter it is easy to become complacent with watering. As bulbs become leafy, the soil is quickly dehydrated and they then need plenty of water. I have frequently seen bulbs in containers damaged by severe water loss in an unexpected spell of dry windy weather.
In grass

Narcissus (together with crocus and snowdrops) are one of the few bulbs with the constitution to naturalise in grass. It is traditional practice to fling bulbs over the ground to mark a random pattern for planting. I recommend this if there are swathes of grass you do not intend to mow until the bulbs have died down. In my own case I want to regularly mow between them and like in my borders I plant  my bulbs in random clumps. As to actual planting I use my border spade to lever-up the grass, shove in a handful of bulbs and tread down. Fancy bulb planters are of no use to me.
I can easily mow around this clump - assuming no snow!
Don't do this

In the wild
My house was originally two farm cottages  and is more than two hundred years old. I imagine a gardener collecting native lenten lilies ‘in the wild’ and planting them in the hedgerow across the farm track, now a busy road! They are still there and set seed. With a little encouragement from me they have made very strong clumps and some have migrated across the road to my own grass verge.
In my two cemetery gardens there are many thousands of daffodils, snowdrops and bluebells. Planted on graves going back a hundred and fifty years, the narcissus had all ‘gone to grass’ and did not flower. This was a result of the heavy cover of weed. Nettles, brambles, ground elder, couch, horse radish with roots thicker than you arm, you name a weed, it was there. It took a couple of years of my Roundup sprays to eliminate the weed. It took two to three years of sunshine for the bulbs to return to flower but they all did. With no further attention other than keeping them weed free, they continue to flourish at Bolton Percy after nearly 40 years. What happened at Bolton Percy ‘by accident‘ was repeated at  Worsbrough fifteen years ago, this time with intent. It was a delight to watch the same succession back to flower. 
Anticipated pleasures












You will recognize a superior camera skill to my own.

Follow my daffodils later in the season

Friday, 22 February 2013

Catching up. No dig: the story so far


When I plucked up courage and started to blog we discussed several titles. None were satisfactory. Brenda suggested that what defined me as a gardener was the fact that I almost never cultivate the soil. As a consequence of my passionate interest in healthy soil and minimum cultivation, I am able to manage large wildlife-rich areas of garden (five acres) to grow thousands of plants - many rare- in a natural manner. I also wanted to pass on the methods I use in my cemetery gardens. I am proud that I created and maintained the once famous Bolton Percy cemetery garden in little more than one hour a week and have continued to maintain it for the past forty years.

I have not yet run out of issues to discuss in my parallel series, ‘Reasons not to dig’ and ‘Why gardeners dig’, but perhaps it is time to summarise and link back to what has been said so far. My posts are rather fluid as to my definition of digging. Sometimes I refer to pure traditional digging, at other times I discuss other deep cultivations such as forking and rotavation
I acknowledge that we gardeners sometimes need to disturb the soil. My fundamental message is that minimum cultivation techniques are best and that contrary to a common opinion that cultivation improves the soil, the opposite is true.The less the soil is disturbed the better it will be. New readers, who quite rightly, associate me with the use of glyphosate, will perhaps be surprised that I fully endorse the proper use of the hoe.
An old fashioned dutch hoe can be use to sever weeds from the ground. But no ‘fluffing up’ please. Note the straight-through action of hoe with no upturned leading edge

Reasons not to dig Why minimum cultivation is best
Bulbs can naturalise in none dug beds

  • Uncultivated soil has a beautiful structure. There is structure at the micro-level, which goes right up to the macro-structure of the whole soil profile. Such a profile is interlaced with connections and channels that provide  aeration, drainage and root penetration going down to considerable depth. Such soil is a living ecosystem for life. 
  • One cultivation creates the need for another. I have not emphasized this enough. When the natural structure is ripped apart, natural processes need to start again. Exposed loosened soil is subject to slaking down in rain, damage by compaction and erosion by both wind and water. Sometimes plough and rotavator compacted pans are so severe that even the none digger might need to dig once in a new garden! Those who cultivate too much are like junkies stumbling from one fix to the next.
  • Clay soils benefit most.The damage to clay soils by cultivation is so great that the soil profile either becomes a structure-less rock in summer or a  wet sloppy mess in winter. The only way out is to cultivate again! It will take a year or two to break out of this vicious cycle but the benefits are huge.
  • Weed control becomes easy. Weed seeds buried in soil might survive for a hundred years. Provided they are not brought to the surface they will remain dormant, After a year or two of preventing weeds seed, surface weed seeds will work out of the system. Apart from time-saving considerations this enables broadcast sowing and self seeding of desirable plants.
  • You can walk on the soil when wet. Because an uncultivated soil is settled and cohesive it will not easily sustain damage when subjected to foot pressure. It is not compacted as you will invariably be told. Compaction is what happens to cultivated soil when wet. In contrast to normal practice I rush out to plant and sow after heavy rain. I always invite garden visitors to walk on my soil to inspect plants.
  • It saves hard work and time. 

Bolton Percy soil is firm and settled but not compacted
Weed free conditions enable winter aconite to self seed
Note the soil brought to the surface by worms

  • There is more life in soil undisturbed by cultivation. More worms and very significantly more mycorrhiza. Gardeners are stilling learning about the benefits of arbuscular fungi which produce glomalin, a hugely important agent in soil formation.
  • Intrusive cultivation oxidizes organic matter away. In none dug gardens the soil frequently become black! I get carried away in my enthusiasm to emphasis how soils become rich in organic matter merely by recycling organic matter naturally produced in situ by photosynthesis. As a result of this prejudice, I have so far failed to emphasize how plots can be speedily converted to no-dig by an extremely thick mulch of well rotted manure or garden compost. Beware however of quick-fix additives frequently found in the trade.
  • In beds and borders cultivation can damage or kill plants. A feature of my own gardens is that plants are healthy.
You might not like the liverwort
Put a mulch over and ensure the soil is undisturbed

It is sometimes necessary to disturb the soil
Healthy sweetcorn


Friday, 15 February 2013

Using iron sulphate to control moss



My neighbours and Brenda - especially Brenda - ridicule me when they see me ‘faffing about’ with the lawn. Some men are obsessive about their lawns and I am one of them! Not in the usual way, with ride-on-mowers and rye-grass stripes, my own ambition is to create a fine fescue-grass turf. Whatever kind of lawn you have, iron sulphate will both improve it and control moss.
Including generous donations to friends and family, 25kg lasts me nearly two years.

The curriculum-vitae of this fine, white, faintly green, powder is most impressive. Not only with regular use, will it ensure a moss-free sward, it’s adherents make the following claims.
  • It’s a fertilizer that provides the essential trace element, iron. When I waxed lyrical about this, a clever student once remarked “but what about the sulphur?”. He had a good point, one of the effects of clean-air legislation has been that our soils no longer receive the essential nutrient sulphur from air pollution.
  • It promotes a beautiful green grass - much more subtle than the dark green promoted by nitrogen fertilizer.
  • Sulphate fertilizers acidify the soil and thereby encourage fine leaved grasses.
  • It discourages turf disease and from my own experience, I think this may be true
  • It is said to discourage worms but the evidence of my own pictures might cast doubt about this. I am happy to have some worms in my lawn for drainage and aeration and many species of worms only cast  below the surface. Any chemical that acidifies the soil will discourage worms.
  • It might scorch broad-leaved turf weeds. I do not regard this as significant and indeed it is an effect I try to avoid when iron sulphate drifts onto my borders.
  • It reduces frequency of mowing but not very much and it’s rather a frivolous claim. It does slightly check grass growth for a couple of weeks after application. I used to tell myself that the time I spent spreading iron sulphate was more than repaid by the time saved in mowing.

Peculiar legislation
A curious consequence  of our pesticide legislation is a result of the fact that pesticides need to be expensively registered. Iron sulphate as a moss-killer is classed as a pesticide. Iron sulphate as a fertilizer can be sold anywhere without restriction. You can use  iron sulphate on your lawn as a fertilizer, but not in theory as a moss-killer! Is that daft or is it daft?
This suits vendors absolutely fine. They can display their expensive registered moss killers (whose active ingredient is iron) and do not tell you that the cheap iron sulphate fertilizer on the next shelf is much cheaper and often superior.
Application 
For a small lawn it is convenient to dissolve it in water and apply with a watering can. In the past I would stir about a kilogram of iron sulphate in an old dustbin to make my own ‘witches brew’. 
An early lesson I learnt when I started to have my own clients was that it is not a good idea to use a knapsack sprayer. It very quickly ‘clogs its innards’.
Some gardeners spread iron sulphate in lawn sand. The purpose of the sand is to aid even spread. Some gardeners mistake the purpose of lawn sand. It is not to improve the physical condition of the soil. The quantity of sand applied when spreading moss-killer is far too small to have any appreciable effect on soil texture.
Poetry in motion

Now that I have 800 square meters of lawn all the above methods are far too slow. I now just fling it! In fact I love the way the fine powder just drifts across the lawn when on a still day I spread it. I have become quite skillful and as you will see from the pictures, I really enjoy myself! I use my lawn to integrate all my garden features and the lawn has a highly irregular shape. Despite this it takes only  half an hour to do the job. If you intend to use my drifting technique ensure that the iron sulphate you buy is powder-dry in a well sealed bag!
Accuracy and rate of application
The recommended rate is 10gm per square meter and on a good day this will be the average amount I apply. I deliberately fail to apply the iron sulphate evenly, I follow the moss! Parts of the lawn get less, some get more. When I repeat the job three months later, it all gets evened up!
When and how often
I fell in love with iron sulphate forty years ago when I read an article in a professional turf magazine written by an Irish green-keeper. He used it six times a year - but then it rains lot in Ireland and moss grows well! I apply it three or four times a year- when the whim takes me! It can be applied any time of year - but note the proviso below.
Worts and all, things that can go wrong


  • It does what it says on the tin, it kills moss and the moss goes black. (Although as stated above, it actually says nothing on the tin). Brenda’s sister was delighted with this sudden effect. Elaine, my bridge partner almost refused to play with me again but we are still together after thirty years and she has a beautiful lawn now. If your lawn is really mossy, first apply it when the grass is growing vigorously so it will cover the dead moss. If you are energetic you can rake-out dead moss. I never do!
  • If you apply it, mix it or spill it on stone surfaces it will give  a rusty stain.
  • If you have delicate hands wear gloves, especially so, if there is moisture around.
  • It has a faint seaweed smell which I rather like
  • In theory if it drifts on wet leaves of plants it will scorch them. I never find this a problem in practice and indeed in winter deliberately drift it onto my borders. Many of the plants enjoy iron sulphate too!

Is it a grenade?

You might like my recent post on lawn fertilizers

Monday, 11 February 2013

Clivias



On our our second day in Madeira we received an e-mail from our neighbours. The heat setting on the boiler had not operated, it was minus ten centigrade outside, the pipes were freezing and the conservatory was zero! Wonderful Harry came to our rescue!
Just in time, both the pipes and the plants were saved. Now, after four weeks, even Brenda’s precious orchids are unscathed! Clivia miniata will stand minus four for a short while, so no problems there.

All Brenda’s plants have survived the cold. The christmas cactus is flowering for the second time this winter.
My first memory of clivia is as a handsome, dark, shiny-leaved, foliage house plant for shady places. It was quite a revelation when I discovered that, when grown in plenty of light, it has beautiful flowers. In our conservatory it repeatedly produces fantastic orange flowers from November to March.

In Madeira, this bulb was to be seen everywhere used as ground cover. Sometimes it was in very heavy shade under trees. It’s flowering season there was over. I’m afraid I was too preoccupied snapping exotic flowers to photograph it, a shame as it was so prolific on the levada walks!

As a house plant clivia likes a large pot. Our two plants are in eight inch diameter terracotta pots. They grow well in a range of composts. Mine are in my home made soil compost - only possible because my soil is sandy. I top dress with my general NPK fertilizer about every two months all year round. Regular liquid feeding achieves the same result, it’s just that I am lazy and it’s a chore.

Our clivias have a summer holiday outside between June and early October. They come back inside when first frosts threaten. A touch of frost is ok, and indeed they should not come inside too soon as a touch of cold aids the initiation of abundant flowers. I have to say in summer they look rather moribund and snails love them. I actually found a tiny snail on my plant today!  Outside, they are kept in an out-of-the-way shady spot.The bright summer light and shock of going outside usually turns many leaves brown. No matter, it does them no harm.


When I bring them inside I give them a little extra fertilizer. They are about to make lovely fresh new growth and will very quickly come into flower. When plants are naturally making growth is the time that they need nutrients.

Although clivias like to be crowded in their pot, after a few years they need to be divided after flowering in Spring. There will be no shortage of takers for any new plants!





Friday, 8 February 2013

Reason not to dig 6: Protecting the environment




This post might best be retitled ‘reasons not to plough’. The effect of a gardener’s soil management on the environment is small compared to agriculture. My recent posts about soil have examined how minimum cultivation helps build-up of soil organic matter and in ‘Why Gardeners dig:5’, how in traditional horticulture, nutrient release from the breakdown of organic matter as a result of soil cultivation, is harnessed to benefit plant growth. It is the detrimental consequences of organic matter breakdown that I want to discuss in this post.
 When organic matter degrades it
  • adds carbon dioxide into the atmosphere
  • releases soluble nutrients, in particular nitrogen, which can leach into ground water.
There is also a problem of phosphate pollution when leachate from organic matter left standing on hard surfaces such as tarmac, goes directly into the drains. Soil absorbs phosphate very tightly and normally there is very little leaching from soil. When wind and water erosion physically takes soil into water, then phosphate pollution will happen. It is significant that erosion occurs when soil has been loosened by cultivation. In the UK phosphate pollution of water courses is principally caused by industry and detergents.


Soil organic matter sequesters carbon
The soil in an established pasture might contain in excess of 4% organic matter. More, if you include the bio-mass of living grass. After 25 years ‘under the plough’ this level might be halved. When considered on a worldwide scale, this represents millions of tons of carbon dioxide released into the atmosphere.
Inevitably when any wild vegetation is brought into cultivation, carbon dioxide will be released. On a global scale the amounts are huge.
Modern farmers can now make their contribution to reducing carbon dioxide release and indeed with enlightened methods, can return carbon to the soil. Although we do not see much movement to ‘no till’ in the UK, on a world scale there are many examples of otherwise vulnerable soils which retain fertility when minimum cultivation methods are used.
Farm field overlooking Yorkshire Wolds. No local fields have been ploughed this year. It has been too wet.
Pollution of water by nitrates and phosphates
These nutrients promote luxuriant growth in aquatic algae and other water plants. When this growth dies it’s decay depletes water of dissolved oxygen, to the detriment of animal life in water courses, lakes and eventually the sea. Not all nitrate leachate entering waterways is from degradation of soil organic matter. Poor fertilizer practices are a significant source of pollution. Organic growers are not absolved of blame - their manures and organic materials also release large amounts of nitrate when they decay. Organic methods, and particularly minimum cultivation, do however tend to minimize this leaching.

Blue lupin as green manure

Agricultural practices that help sequester carbon
The modern farmer can do much to maintain a fertile soil and restore the soil after the detrimental effects of poor past practice.
  • Converting to minimum cultivation methods. Farmers can use shallower soil cultivations. It has been shown that deep cultivation, other than to break up a known cultivation-pan, brings no agronomic benefit, uses far more energy, and greatly increases loss of soil organic matter. 
  • For many crops the use of herbicides ends the need to cultivate for weed control.
  • Farmers can follow one crop immediately with another. Far better than overwintered, ploughed fields leaching nitrate.
  • Use of green manures.
  • It is traditional practice to ‘repair’ damaged agricultural soil by grassing down for a few years. Recent research suggests that inoculating grass seed with mycorrhiza, which add glomalin to the soil, will accelerate this process.
  • Carbon can be directly sequestered in the soil as biochar. I will soon be blogging about the enormous benefits of adding charcoal to the soil!





Tuesday, 5 February 2013

My poor Garrya elliptica

Garrya elliptica  ‘James Roof’ - the silk tassel plant


Whilst we sunned ourselves in Madeira, it was minus ten centigrade for four nights at home and not much more during the day! We came home to a somewhat scorched plant. The books say garrya is ‘hardy down to minus ten’ but I think it will normally stand more cold than that. As far as I remember, in the much colder double winter of 2010, mine did not turn a hair. The significant thing this year, was that the cold was preceded by a warm spell. This is not a happy combination.

Poor thing

I recall over the years, when I used to have clients in various parts of Yorkshire, this brown scorch happened on only two occasions in ten years; once in November and once in March. In both years it was the same combination of weather, a sharp change of warm weather to cold. I found it interesting that the same thing had happened in every garden I worked.

Happier days

What shall I do now? Nothing for several weeks. It is best for any die-back to take its course and then prune it away. The level of damage is actually quite small. By May there will be no evidence of my present problem.
Starting to cover oil tank
Garrya elliptica is one of those shrubs that is best grown and trained on a wall. Wall shrubs  need pruning to stay on a wall. Some gardeners seem to think wall shrubs will grow as elegant wall hugging plants without help! Dream on. Although garrya will grow on a wall of any aspect, they are one of those special plants that thrive on a north wall. My own plant faces north-east and I was retraining it to cover an oil tank that we had to replace last year! 
Interestingly, the lovely catkins are male (well, he is called James!). As long as you do not prune back after early summer, they will flower well from November to March each year. 

A setback to covering my tank!

The most exposed garrya shoot sustained the worse damage. Hydrangea petiolaris is covering from the other side. It seems the plants themselves will decide how to camouflage the tank!

up date on my Garrya which now in May is starting to sprout on this post on sudden shrub death



Friday, 1 February 2013

Mulching with gravel and stone

Schizostylis loves the extra moisture under mulching stone

Many years ago a student said to me  “if you are so keen on zero cultivation, why don’t you put a mulch over the ground and gain a further whole series of advantages?” I do agree. Today, I will confine my comments to covering the soil with none water-absorbent stoney materials. Mulches in general, have many advantages, including conservation of soil water, weed control for ‘weeds-from-seed’ and provision of design opportunities. Plants just love the conditions created by stones and gravel. I have to confess that my secret belief is that the greatest benefit of mulch is that it prevents the over enthusiastic gardener scratching away at his soil!
I was first converted to gravel mulches forty years ago at Askham Bryan College when at the then annual conference for Parks directors, the speaker almost as a ‘throw away line’ mentioned how he mulched borders throughout his town with a two inch thickness of ‘pea gravel’ (purchased from a builder’s merchant it is still my favourite mulch). The revelation caused a mild sensation and he was bombarded with questions such as “what if you change your mind?”  “what about vandals using the pebbles as missiles?”  what about accumulating litter?”  “what if you have not eliminated perennial weeds?”
It never really caught on, but never-the-less you still see fine mulched landscaping, albeit more often with larger pebbles, mulching stones, small rocks and un-cemented paving.

Nerine, arum ophiopogon et al

The first gravel garden constructed at the college was a large educational display of ‘dwarf conifers’. The border was prepared conventionally and covered with thick black polythene!
The plants were inserted through slits in the plastic and the whole thing was covered with a thick layer of gravel. The conifers thrived for twenty five years and over that time no more than a total of a couple of hours was spent pulling out the occasional opportunistic weed. Visiting parties always asked “but how do they get water?” The fascinating thing is that they do! Water gains access through the planting holes and from the edge of the plastic. As a consequence of a repeating cycle of evaporation and condensation beneath the polythene the covered soil remains uniformly moist. 
In the end, the border suffered the normal fate of all so called dwarf conifers. It became a forest! 

On a Winter morning-today!

Nowadays people tend to use ‘mulching fabric’ rather than polythene. Although the use of gravel-covered plastic is anathema to me, it is an excellent labour-saving approach for fairly permanent more static landscape features. In the past I have created gravel gardens for clients who no longer wanted to mow their lawn. Its so easy, just spray off with glyphosate, cover with plastic, slit in nice plants and spread gravel. Hey-presto an easy garden feature that lasts for years.

The whole of my front garden is mulched with builder's gravel

Why I don’t use plastic 
The reason I do not use plastic in my own gravel gardens is because it is too restricting. I want  plants such as hardy cyclamen, creeping thymes and dwarf tulips to seed themselves. I want delicate alpines and hardy cacti  to spread. When I acquire a new precious plant I want to easily pop it in. Because I use glyphosate I do not need underlay to prevent weeds nor do I need to spread gravel at the usual  two inch thickness.

I plunge these golden torch cacti for eight months of the year

Choice of plants
Herbaceous, bulbs, shrubs, alpines, annuals and biennials, for me any category of plant will do. Gravel gardens are perhaps less suitable for dense plantings such as herbaceous borders, for vigorous vegetation and ‘plants that run’. I recently inspected a gravel garden where bamboo had taken over! (It was easily cured with a well directed glyphosate spray).

Gravel is a wonderful place for seed to germinate
Another Cyclamen coum taken today

Wonderful water conservation
We might forget in this wet year how precious is summer moisture (although the current fashion of planting-for-drought might fade more quickly than most gardening fads). All mulches have merit for water retention but I think  gardening literature fails to recognise  the superiority of gravel and plastic. Spongey materials at the soil surface will intercept light rainfall. Stone is none absorbent  and rain percolates through. Much of this water is preserved from subsequent sunshine and drying wind. I liken gravel to a one-way-valve for  water and I think this is the main reason why plants thrive when mulched with gravel and stone!

Winter aconites push through

Link
I have recently written a more extended article on mulching
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