Friday, 30 March 2012

Some like it hot, many aren't too fussy.

To follow on from my last post about efficient use of water in pots I wanted to give you a glimpse of the way I decide where to position which plants during the summer. These are just my opinions, based on a lot of trial and error (and in this space I can't provide a comprehensive guide) but they may be useful to those of you who are wondering how they are going to keep your potted plants happy in a difficult year. If you are a beginner at this please don't be afraid to try, and to make errors. You may marmalise a few plants along the way but if you observe them carefully and if necessary move them, there will be few fatalities...
Succulents with their feet under terracotta gravel can take the heat. July 2007.
A basket of dahlias by itself - you'll
need to keep an eye on it... Sept 2009
Where is your pot?
Pots on their own, in a hot, dry location such as our stock yard, are difficult, especially if they are raised up and exposed to more drying wind. Succulents and a good inch of gravel mulch are the answer.
Even in the relatively lush courtyard garden, a pot by itself with a plant that requires plenty of water (such as this Dahlia Gallery 'Rivera', left) must be near a path where you will see it regularly, so that you can pounce on it if it starts to wilt. Try to keep it in part shade.
June 2008. Conventional mixed
planting in a Ham House Urn in the
drive of the pottery. Watering cans
needed regularly.

Over exposure
The Ham House Urns in the drive may be on the northern side of the hedge but they are exposed to the drying wind and too far away to water regularly. 
Sept 2011. Succulents in Ham House Urn
in the drive of the pottery.
No watering necessary!

I have had success with mixed plantings there with much lugging of watering cans. In the last two years, however, I have simply filled the pots with succulents and left them to it. No watering at all from early June to October, when they were dismantled.

Aeonium arboreum 'Zwartkop' on top of the well
with Pelargonium 'Duke of Edinburgh' and
Cineraria maritima 'Cirrus' doing fine but
the Lobelia and Verbena are struggling.
Sept 2007

In an exposed position you can mix large succulents, especially aeoniums, with other plants such as pelargoniums, cordylines and phormiums which revel in large dollops of sunshine and are fine with occasional dryness.

Shady deals
Many bedding plants which are often recommended for hanging baskets are surprisingly intolerant of drying. Lobelia and Nemesia for instance, may not die immediately but they will soon sulk, stop producing flowers, and keel over earlier than necessary. Many bedding Verbena will be susceptible to powdery mildew if allowed to get too dry too. Give them good light, but shelter from the wind and the hottest sunshine of the day.

Agapanthus like a front row seat
for sunshine. I think this is 'Bluety'.
July 2007
As for the smallest pots - well, in sunny positions I only put succulents in them for high summer. That way most of them won't need watering at all. If you have a collection of smallish to medium pots it's best to favour plants labelled 'drought tolerant' because even in a shady position it is easy to forget them and let them dry out - at least these pots have the advantage of being dunkable. Just put them in a tub of water which comes half-way up their sides for an hour or so, but don't forget them and leave them to drown!

Bring me sunshine
As mentioned in the last post I group the pots together for maximum humidity/coolness, but something has to go in the front row. Apart from succulents I often choose Agapanthus  or Nerine for this role as they enjoy a good baking.

Astelia chathamica 'Silver Spear', Plumbago
auriculata, Convolvulus cneorum and
Convolvulus sabatius thriving in a south-
facing site and a big Wisley Gardener Pot
September 2009
Drought tolerant/sun-loving plants often have grey or blue foliage, the heat-stress avoidance techniques associated with this colour include waxy coating on the leaves or a layer of fine hairs. Luckily for us gardeners this makes a tasteful selection of foliage in a sunny spot pretty easy at the same time as being water-efficient. Try plants like Cerinthe major 'Purpurascens', Astelia chathamica 'Silver Spear', Elymus arenarius, Festuca glauca, Lavandula x christiana, Argyranthemum foeniculaceum, Dichondra micrantha 'Silver Falls', Convolvulus cneorum and Convolvulus sabatius.

...and only sunshine.
Of course many of the sun-lovers won't flower well in shade. Plumbago auriculata and the pelargoniums, for example, need good light to flower profusely. Convolvulus cneorum/sabatius, Osteospermum and Gazania  flowers will stay sullenly closed in deep shade, and don't even think about putting Ipomoea tricolor (Morning Glory) in shade. Of course that doesn't mean that the bases of these plants need to be exposed to sun, so you can crowd other plants in to shade the surface of the planting and minimise evaporation.

Ipomoea tricolor 'Heavenly Blue' with its head in the sun of the entrance to Whichford Pottery but its toes
under lots of other plants. July 2010
Nasturtiums (Tropaeolum majus) flower surprisingly well in shade. I have used them in indoor flower shows in Japan and they were unique in flourishing and flowering with NO natural light in a department store! They will cascade just as happily over the shady side of a large pot as over the sunny one, so this is something to bear in mind if you are trying to save water by keeping most of your pots in shadier locations than usual. Petunias will be all right in part shade, too, and Nicotiana.
Tropaeolum majus (nasturtium) on the northern side of the entrance arch. July 2009

Fuchsia 'Bornemann's Beste' flowering well in
deep shade by the staff room, petunias and
pelargoniums are managing too. Sept 2010
Some plants deserve to be popular
There are quite a few plants which will happily flower in shade. This year we are denied bedding busy lizzies (fine if you choose the colours carefully, don't be snobbish!) because of a plague of downy mildew, but I cherish my plants of their huge perennial cousin Impatiens sodenii, a fleshy giant with white flowers which reaches 5-6ft tall given the chance. There are lots of good begonias and beautiful fuchsias too - don't let the fashion police deter you - which will flower well in the shade.

Of course all your foliage plants can be stuffed into shady corners to save water - but beware of putting snail food, like hostas, close to walls, as hungry molluscs will abseil down, grateful that they don't have to crawl over rough terracotta for their supper.

Undeniable thirst
Some thirsty plants, especially those grown for fruit such as strawberries, tomatoes and blueberries, work best with some sun at least so it is worth sitting their pots in saucers to catch any water draining out. But if the forecasts are wrong and it rains a great deal only the blueberry will be happy with its feet constantly damp.

Think before you plant
I have a wide-ranging collection of plants, and I'm not about to chuck them out because watering will be more difficult this year. But I am going to think very carefully about where to put them. It may be that many of them will have to be be in shadier places than is ideal, so perhaps they will produce fewer flowers, but at least I'll still have them when/if our climate regains its sangfroid.
The Salvia leucantha and annual Lupinus 'Summer Spires' in these pots would produce more flowers
in a sunnier spot but still look pretty spectacular in a lightly shaded position and require less water.
September 2007

Saturday, 17 March 2012

Watering terracotta pots - not such a problem as you might think

My apologies for the length of this post, but I wanted to tackle this topic thoroughly...

Now that hosepipe bans are certain for many areas of the country from next month I can see that panic about terracotta pots may spread. I am tired of reading articles which baldly state that terracotta dries out much more quickly than plastic and therefore should be avoided. Time to stick my oar in.

Terracotta terror is unjustified
July 2008 Happy plants in terracotta in our hot, dry stockyard.
Not as difficult as you may think
Visitors to the pottery sometimes assume that I spend all my time watering the 300-500 pots on display. In a typical summer I water 1-3 times a week, depending on the weather. After all I'm only there three days a week and I have plenty of other tasks! I do ask Babs to water at the weekend sometimes for me.
It takes about two hours to water the displays with water running at watering can speed from the hose. Some plantings may need an occasional top up from a watering can. I have about 200 pots at home and usually use a watering can with rainwater or water from the kitchen sink - it's manageable...

In my view it is not the pot material that makes the difference to the quantity of water needed, but the establishment and maintenance of correctly chosen plants.

An established planting in a high-quality terracotta pot does not dry out perceptibly more quickly than in plastic. In a plastic pot the sun heats the root ball more than in cool, porous, insulating terracotta and so it could be argued that more root damage and evaporation may occur. I have not tested this scientifically, but I have been working at Whichford Pottery for eleven years and was obsessed by gardening long before that: at the beginning of each summer I plant hundreds of pots and yes I use plastic at home (being a plantaholic I use anything) as well as Whichford seconds and I can truthfully say that I find the terracotta easier to look after.

When a planting has become well established the fine roots of the plants bind themselves to Whichford terracotta so that if the potful is allowed to dry out at all the rootball does not shrink away from the pot. In plastic the rootball shrinks and a gap is left all around the container so that most water arriving from above runs uselessly down the crack instead of soaking in to the compost.

Lining terracotta with  plastic prevents the roots from binding on, denies the roots oxygen and can interfere with drainage - please don't!
I believe that the vast majority of water lost from an established pot is transpired from the foliage and relatively little is lost through the walls of the pot. Before plants are established and there is un-colonised compost in the pot it does more harm than good to have excess water sitting in the compost, so even in a warm summer good drainage (as in Whichford pots) is very important. Good drainage is sometimes confused with "drying out".
Plastic pots which are allowed to become somewhat dry are also likely to blow over and break precious plants.

Here are my tips for surviving a water shortage with a fine display of pots:

Location, location
Be aware of your garden's microclimates. Remember that pots, even big ones, are moveable! If watering is going to be tricky this year it makes sense to revise your usual display sites and if possible locate most of your pots in at least part shade, preferably keeping them out of the sun in the hottest part of the day (early afternoon). Put them within easy trudging distance of your water butts.
Put the right plants in the right location - sunlovers in sun, but leafy water-lovers with more shade. I'll go into plant choice in more detail next week.
Transpiration (water loss from leaves) rates go up dramatically in windy positions, so keep pots away from exposed sites if possible; bear in mind that walls can look sheltering but may create damaging turbulence and surprising dryness, especially near corners. Use semi-permeable barriers to reduce this effect - trellis, willow obelisks or woven screens, even garden benches can help.
Be aware that a shade-giving fence or house wall may also create a rain-shadow, so that a pot at the foot of the wall receives less of the precious wet stuff.
June 2009 Hostas do very well in Whichford Pots
Here they enjoy the shade on the northern side of the Octagon
but I have to remember that here they are sheltered from rain as well as hot sun
May 2010 One I got wrong. By the time the Humulus lupulus 'Aureus'
had covered this obelisk there was too much foliage to be supported
by such a small pot. I had to keep watering it, even after
moving it from a much windier, sunnier location.
Choose the biggest pots you can afford. The bigger the pot, the easier it is to look after - small pots have a much greater surface area to volume ratio and so will dry more quickly, they are also more fiddly to water. 
When you plant a pot bear in mind the eventual size of the plants. My rule of thumb is that a certain volume of compost/roots will happily support up to about twice that volume of greenery, experience teaches you to vary this according to site and plant choice. It's particularly easy to get it wrong with vigorous climbers.

Most of our really big pots have a base ring which can be taken out so that large plants, trees etc can root through into the ground below to find more moisture. Bunny Guinness often recommends this. Of course you need to be very sure where you want your pot to be!

Group mentality
Clustering pots together creates a more humid microclimate around the display, slowing transpiration; they shelter each other from sun and wind and dry out much less quickly than a pot by itself does.
As the plants expand you can move them slightly further apart. A group is easier to water and has much greater visual impact too.
Sept 2007 This group faces south-west but is still luscious in late summer, helped by its own microclimate

Compost considerations
I use a compost which is a mixture of peat, loam and grit. One feature of loam content is that it makes the compost easier to re-wet and the clay in the loam will hold on to moisture and nutrients. You can add water-retaining polymer granules but I don't because I like to keep many of my plants for overwintering and I find that the granules increase the likelihood of rotting in the winter.
These well-established plants (ALL in pots)
are on a hot,windy corner but are not overfed
and are surprisingly tough. July 2008
I add a little slow-release fertiliser so that I won't have to use soluble fertiliser. I don't feed my plants much because I want them to be tough - I don't need them to be enormous and floppy, I want them to be strong, healthy and fairly compact, needing less water.
I keep watering to a minimum before the plants are planted in the pots too (without allowing them to dry out completely), and have always thought a little neglect now and then toughens plants up - it seems that someone agrees with me (click here to see an article on the possibility of training your plants to drink less)

Give them a good start
Fast establishment of summer plants is key. Thoroughly water the plants you are going to use, then leave them to stand for a couple of hours before you start. This means that the roots slide nicely out of the plastic without being damaged, and the root balls are soft but not waterlogged, so that the roots can carry on growing outwards to colonise the fresh compost without check. If you plant dry rootballs and water them in, much of that water will bypass the hard, dry rootballs and drain through the damp compost.
Make sure that all spaces between the plants are well filled in with compost so that there are no gaps and the rootballs are all covered, then water thoroughly immediately and check that the roots are still thoroughly covered. The surface of the planting should end up about 2cm/1" below the rim of the pot so that there is room to water without washing the compost out of the pot.

Sept 2009 The base of a standard holly tree, mulched with gravel and stones
Mulchy, mulchy
If there is quite a lot of bare compost still to be seen when you have finished planting, a mulch of gravel, pebbles, grit, slate, glass nuggets etc will help to slow evaporation and will stop the surface of the compost from forming a hard cap which prevents water from penetrating easily.
I plant summer pots pretty densely, so that little compost is visible, the plants then knit together and shade the surface and ultimately the sides of the pot. Watch out for large-leaved plants covering the surface of the pot - you may need to water even after rain as they may act as an umbrella.

A proper drink
If your water authority allows it a drip irrigation system is really useful and economic. Ours has been ruined by dogs and utilities excavations, so currently I use the hose and watering cans. Make sure that enough drippers are placed in each pot to avoid dry patches. For the summer set the timer to work in the evening so that the water can soak throughout the potful and be available for all the plants before it starts to evaporate.

Whether you use a watering-can, a hose or an irrigation system the principle is the same. Give a good soak as infrequently as possible at a cool time of day. Do not allow pots to dry out between waterings as there will be run-off because a really dry rootball is hard to re-wet.
Do not water little and often as this will not encourage the roots to colonise all the available volume of compost and will encourage soft and unsustainable top growth. I count (to 60 for a medium-sized pot, 100 for a big one etc) to stop myself from moving on too quickly, and I water at several different points in larger pots.

I never use a spray or a rose, I simply have the water pouring gently and steadily so that the compost is not blasted out of the pot. I sometimes use my thumb to spread the jet slightly if I'm using a hose, the aim is not to wet the foliage and flowers but to get as much water as possible to soak in around the plant roots.

To test whether a planting is dry do not just look at the surface. Observe the plants - are they turgid and happy looking or are they starting to wilt? Stick a finger right into the compost to assess its moisture content.
The Echium pininana in the centre of this picture is looking quite happy...
Sept 2008
But the Echium pininana here is beginning to look
sad - I may have to water today
July 2010
If you observe the state of your compost and plants regularly you will soon learn the warning signals. I use some plants as miner's canaries - I find Echium pininana and Salvia confertiflora are the quickest to show signs of distress, so if they have started to look sad it is time to get watering. This way you can avoid other plants get stressed and keep them flowering and free of powdery mildew.

Paradoxically, if a summer shower is predicted after a dry spell it may be worth doing a light water beforehand to make the compost surface more receptive and to make the plants turgid enough not to get broken by the downpour.

So please don't let the prospect of a hosepipe ban stop you from enjoying your container gardening - look on it as a challenge which will make us think more carefully about making the most effective use of any water we do use!

Wednesday, 7 March 2012

The Whichford Hecklers - some more pottery people

The noisy people upstairs.
Andy is on the left, Jeannette standing behind him, Simon is on the right
and Hilary is falling out of the middle.

I would like to introduce you to two of the mainstays of the pottery, if you collect Whichford pots you are quite likely to own one made by either of them - just look for a maker's mark at the base of the pot - one is represented by a fish, the other by some rune-like squiggles (crotchet rests?).

Andy back in the dark ages with sweet little Adam Keeling
Adam is now a thrower at the pottery and married, with four children
Long service medal
If you climb the stairs to the main throwing room the first person you are likely to meet is Andy Gill. This is apt because he has worked at the pottery for 30 years, almost since its foundation. I find it hard to imagine him as a teenage apprentice now but he must have been one once.

Nowadays you will hear him grumbling about his aching knees and shoulders, but he is young at heart,  and a great cook and host with many friends and an endless stream of dodgy deadpan jokes. When you hear gales of laughter echoing around the pottery Andy is the likely cause.
Mention pies when you meet him and you'll have his full attention.
Simon singing at the staff barbecue in Jim's garden
with Jake, who is Andy's son.
Don't give up the Day job
At the far end of the room you'll find Simon Day, who also has about 30 years' pottery experience and has been at Whichford for the last eleven of them. He's a talented musician and every now and then he allows himself to be persuaded to bring one of his many guitars and play and sing for us at work. When we all went to Jim's house in France one year Simon's guitar and the Beatles Song Book came too and we sang raucously into the night. The neighbours must have loved it.
Mention fruit of any sort to Simon and he will talk for hours, and hours...



Simon and Andy are a natural double act, if I need cheering up I just have to spend ten minutes with them to find my laughter again. During the summer they will lean out of their windows and hurl abuse at me like Statler and Waldorf from the Muppets, so don't be startled if you arrive to find the gardener apparently shouting into thin air, I haven't been drinking, I'm just dealing with hecklers.

Hands on
It is Andy who teaches throwing at the one-day pottery workshops here and he's a patient, friendly and funny teacher. All the makers here are friendly so if you come and have a look round they will be pleased to explain what they are doing if they have time, although sometimes they are under pressure for a big order or need to concentrate on a tricky process, so may not have time for a long chat - but we are all proud of the standard of craftsmanship here and would like to show you what goes on.
Tandem pot throwing

I have only ever had one go at throwing a pot (and produced one small, wobbly pot with a lot of help) but this was enough to show me how physically hard this must be to do all day. The clay is heavy, cold and wet. It looks smooth but it contains grog (see my post about the clay) so as it spins it feels like wet sandpaper, you have to apply a deceptive amount of force to shape it, which is hard on the fingers, wrists, elbows, shoulders, back... And a moment's inattention can have the whole thing collapse back into a blob.

These two make it look easy. They can even throw in tandem (see left) or with their feet (click here).

Making the top section of a
rhubarb forcer

Size matters
Andy and Simon both make a wide range of items, but Andy's speciality is the two-piece pots. These are usually about 30-36" diameter, using up to 120 lbs clay in total. Andy throws the bottom half of the pot and transfers it to another wheel, then throws the top half to exactly the right size and fits it to the bottom section. Sounds simple? Not many people can do this.
He has also designed some of the pots in our range, including the best-selling Buxus pots.

I am adding making videos to YouTube - click here to see Andy in action.
Andy makes our famous rhubarb forcers, which can be seen in both humble and prestigious gardens all over the country, including Raymond Blanc's Le Manoir aux Quat'Saisons. He has started making extra-large ones now, so even bigger clumps can be forced for tender, sweet stems.
Checking the finished height of an XL rhubarb forcer

It's very hard to photograph throwers
without making their elbows look huge!

Small but beautifully formed
Simon makes a wide range of flowerpots, usually smallish to medium size. We like to tease him that he can't make big pots but of course he can. He also makes lovely mugs and so-on at home, I have a gorgeous, rounded blue one which is a pleasure to drink from and I get VERY ANGRY if anyone steals it at break time!
Simon throwing - note the high tech measuring device
(a stick)

Both men are very disparaging about their own talents in that peculiarly British way, but both have extremely high standards and a quiet pride in their work. Just don't tell them I said that when you come to visit...
Give us a lift! Even medium-sized freshly-thrown pots are extremely heavy