Thursday 30 April 2015

Potato day(s)

With April I have started spending more time in the veg garden, up to 2 days a week, which is something I have worked to achieve, as I expect that veg growing will be a relevant part of my future involvement in horticulture.

One of the first crops that I've been involved with has been potatoes.

I staked some early potatoes 'Jazzy', which had been grown in bags after being started indoors in week 13, which we then displayed in the glasshouse in the veg garden.  

Potato 'Jazzy' being stakedPotato 'Jazzy' in the glasshouse
Potato fertiliser

I fertilised the soil where potatoes would go in in week 14 (end of March) by top dressing it before the rain came. We used general fertiliser at 10 g per sqm.

Today (week 18) I planted some second earlies. At 40 cm between them in rows 60 cm apart, we planted them at 10 cm depth, by using a marked stick and adding 50 g potato fertiliser per hole, well forked in (it will need another 50 gr as topdressing at emergence, in 2 weeks).

Marking the spacing of potatoPlanting at the right depth

As we were expecting one of the last frosts, I was also asked to earth up the other potatoes  that had emerged. With soil from either side of the row, we covered every single leaf to avoid it getting damaged. 

Potato 'Catriona' earthed upWeek 20 and 'Catriona' has emerged
again, safe from frosts now
We had some sweet potato (Ipomoea batatas) slips too so I was shown how to root them in propagation, by laying them in a tray.

Rooting Ipomoea batatas

Wednesday 29 April 2015

The mint collection

It was the end of February when I helped in the herb garden to remove the mint from its bed for propagation purposes. I was struck at the time that you could count be so many different scents of mint, but there was not much left in the pots that we removed from the ground to sample them well (some mints had completely died back and there were only some rhizomes well hidden in the compost to be found) .

Today, however, I had the opportunity to help pot up the mint that had been propagated and to take it back to the display area in its new pots, so I could try and small a few of the cultivars, albeit by no means all of them.

There are no less than 25 species of Mentha* (22 are listed in PFAF database).

Mint, however, is quick to hybridize so identification is often difficult. To complicate matters further, in common language the word "mint" does not refer only to the genus Mentha, but often to other plants either within the family Lamiaceae (for example, Korean mint, Agastache rugosa, or mint bush, Prosthantera spp) or even in other families. In the latter case, it is the resemblance in the fragrance that promted to use the name (i.e. Vietnamese mint, Persicaria odorata is in the Polygonaceae family).

They main compounds that make of Mentha the economic plant it is are:
  • menthol, an antiseptic, decongestant and analgesic, that is present in high concentrations in M. x piperita, peppermint but also in spearmint (M. spicata)
  • pulegone, a neurotoxic, abortifacient substance, present mainly in M. pulegium: pennyroyal
  • diosphenol, a diuretic, M. longifolia
  • carvone, the substance that links M. spicata and Carum carvi (caraway)
Mints are used for culinary (sauces and drinks) and medicinal purposes, that range from antiseptic, antibacterial, antiinflammatory, antispaspodic and antiparasitic, to being a stimulant**. Oils are used in fragrances and for aromatherapy to increase concetration, and reduce headaches.

Some of the mints in February

Mint, especially in pots, is prone to root aphids*** (possibly overwintering Ovatus crataegarius, the mint aphid) attack, so propagating plants and using fresh compost every year helps managing infestations.

Root aphid on mint
While digging the pots out, we also found a carnivorous slug, new to me, rubbery and engorged on something, likely Testacella scutulum, with a string of eggs. That was rather fascinating.

Testacella sp slug

But, back to today, from 9 cm pots I planted the mint into the 7.5 l pots where it will spend all the season, limiting the risk that its roots will become invasive. We used 2/3 plants per pot to get enough plant material for display (some people will pull the leaves to smell them), but one would be enough if you are not in a hurry.
Some of the mints, before and after propagation

Some of the mints ready to go out in April

The scent I preferred, from all the mints I sampled, was "basil mint", which smells of basil and, depending who you ask, is either M. x gracilis or M. piperita x citrata 'Basil'.

My time in the herb garden after bringing the mints out, however, tells me the most popular, especially among the kids is the "chocolate peppermint", it must be because of the name! It does really have chocolate undertones, but it's very much menthol-scented, which I have always found gives me headache. Except in one case: a few years ago I loved a cosmetic product made with a very strong menthol mint, M. aquatica - which is incidentally quite pretty, with its globose flowerheads, but unfortunately is not in the collection, as it requires wet conditions to grow.


*Bown, D (1995) The RHS Encyclopedia of Herbs and Their Uses, London, Dorling Kindersley, pp. 158-159 and 311-312
**McVicar, J (2007 revised ed) Jekka's Complete Herb Book, London, Kyle Cathie LTD and The Royal Horticultural Society, pp. 154-157
*** Buczacki, S and Harris, K (2005 3rd ed) Pests, Diseases & Disordrs of Garden Plants, London, Harper Collins Publishers, p. 176
 See also the website of the National Mentha Collection in Wales, at and the electronic version of Maud Grieve's A Modern Herbal (1931) at

Monday 27 April 2015


Back in January, I was asked one morning to join a colleague, who was going to collect scion material in the orchard.

Under the aegis of the fruit specialist at RHS garden Wisley, the collection gets regularly propagated to renew old plants and to replace sickly and dead ones (I helped before with the gooseberries). But material is also sent to other gardens and collections, and it is possible to request propagation material from the RHS on payment of a small fee.

So, armed with a list of required cultivars and their locations, a bucket, sticky tape, a Sharpie and sharpened secateurs, we trawled the orchard.

Scion needs to be pencil-thick, one year old well ripened wood (brown, not green), with relatively short internodes. Sometimes you can try and use two year old material if nothing else is available, but it's usually better to plan in advance: cut back hard the plant you want to propagate in winter so than it will produce new shoots that you can then propagate a year after.

Checking that it was not affected by mildew, we took two-three cuttings from each cultivar (if available), we taped them together, marked them with their name, placed in the bucket, and so on.

Scion material, ready for storage
Once back in the messroom, we shortened the cuttings to 60-70 cm for easier storage and posting, cutting from either the tip or the bottom to try and get the longest pencil-thick part. Then we wrapped the bottoms with 4 layers of wet but not soggy paper towel (wet then wrung) and sealed them into plastic bags, writing indications for retrieval. They were then stored in the fridge, awating their destiny.

... because grafting is best done in March (and into April), with dormant scion but awaking rootstock. Budding is however done in the summer, July to September (depending on the type of fruit, with a window that more or less follows the succession of flowering: Prunus, Pyrus, Malus) with dormant buds from plants that have started to slow down.

So fast forward to today, and I've finally had the opportunity to make use of that scion material I gathered almost 3 months ago (gee, time flies).

For the third time this year I had the fruit specialist all to myself, teaching me whip & tongue grafting. We performed it on M26 stock that was planted in the nursery, which was cut to anything between 15 and 30 cm. Too low, and the splashing from rain may contaminate the graft, besides, it might start to root.

The tools required today were: sharp secateurs, a *very* sharp knife (it must be able to shave, and some steels are better at that than others, I'm told German brand Tina is good), white labels, Sharpie, grafting tape, hot wax. 

After a brief demonstration, I was given some spare cuttings to practice on. I felt so hawkward!

Demonstration of cutting a whip
Starting from the bottom of the scion, but having made sure to remove any wood that is too hard with tiny buds, one has to make a smooth, sloping 3-4 cm cut the other side of a bud (the stock bud). One has to pull the knife from the top to the bottom, towards oneself. I found that wearing a plaster on my thumb made me feel safer while I got used to the maneuvre, which starts with the bottom and uses the whole blade lenght to the tip.

Then, starting in the top third of the slice (above the stock bud) and rocking the knife upwards at an angle, one has to carve the whip that will lock the graft together. It is very easy to split a whole lenght of wood if one is not careful when doing that.
Last but not least, the scion is cut to 3 buds (4 if they are very close).

The scion is ready

Usually, the top one (or any one) will start to grow, but if they all go, then one chooses 2 and shortens them to 3 leaves: they will photosynthesise and feed the new tree! They are then removed in August, if the main shoot has grown strong and sturdy.

Then one moves onto the stock. During the whole procedure, one has to be careful not to contaminate the tools or the material with soil, which may carry pathogens.

Measuring the scion cut onto the clear side of the stock (no buds, as they are hard), previoulsy cut to a slight slant, one then proceeds with the opposite maneuvre to the scion's.

Demonstration of cutting the stock

Starting from the the bottom and slicing upwards (astride to the stock), one makes another smooth,
slanting cut, rather superficial, that is making sure one does not goes too deep into the wood. Then, just after the top, at an angle, one rocks the knife to cut a whip here too. I found it particularly difficult to find the right angle for this whip, as it came out too thin a couple of times.

"Church window"
The scion and stock's whips are then joined together, so that a "church window" remains visible: that is because if the bark of the stock were to touch the bark of the scion, they would not join together (as the bark has no cambium) and cause a weakness in the graft.

To complete the procedure, the graft is bound really tight with grafting tape (clear plastic, sometimes biodegradable) by wrapping it around, from the bottom of the graft towards the top, with a slight overlap to keep it in place and only making a fastening loop at the top. One has to make sure not to cover the cuts, because those will be treated with hot wax, so as to conserve moisture.

My first decent graft!

I started with 3 grafts of 'Barnack Beauty', feeling rather frustrated by the results, but fourth time lucky and my graft of 'Barchard's Seedling' was satisfactory, and the next one made me proud: it was firm even before wrapping with the tape!

Of course the closer the size of the scion and the stock, the better the cambiums will align, but sometimes the scion is smaller, like in the picture.

It was rather interesting to have a go at waxing the cuts, and to try hot water melting pot kit.

Melting pot

Oh, I had so looked forward to this day! And, as some scion wood went spare, I will have some more practice in the evenings.

Wednesday 22 April 2015

Coppicing and Coppice Crafts

That is the title of a book I borrowed from the library to learn a bit more about coppicing, as back in February I joined my colleague on a trip to the RHS coppice in Wisley village to cut some hazel for sticks, and fell in love with the magic of the place, albeit slightly derelict as it is has not been actively managed for a while.

The hazel coppice in Wisley  village

Candlesnuff fungus (Xylaria hypoxylon) on rotting stump

We cut just a few sticks, that were of the right size for our purpose of supporting sunflowers: 3 m long rods that were not too thick at the base. But what is the best way to coppice a stool? Some of the stools were cut higher than others, part of the stumps had died back and were rotting: how high does one cut a stool?

Marbling effect in rotting stump

 I came away from the coppice with a lot of questions, and wishing I onwed a piece of woodland, I thought back once again with longing at all the ones that I always see up for sale in Devon, on my way to an holiday.

The book tells me that hazel coppices are usually managed in a 6-9 years rotation. In the UK, they are usually part of a coppice with standards silvicultural system, which means that the short-rotation coppice is interspersed with longer lived standard trees, that make up about 20-30% of the canopy, and are coppiced in turn on a longer rotation.

I also read that the most productive hazel coppices have a stool density of 1000/ha that is a 3 m x 3 m spacing.
I observed when I was on site that good spacing is essential for dragging the wood out the coppice, but apparently closer trees grow straighter rods as they compete for the light. And, in any case, coppicing should be done by area (or "coupe", that should be no less that 50 sqm according to the authors) rather than picking the odd rod here and there, because the cycle of shading of the ground (at canopy closure, to get rid of all undergrowth and make for a safer working environment) and light (to stimulate growth in the coppiced stools) are all important for the coppice health and ecosystem, with all the attendant biodiversity.

The rods we gathered, graded and bundled

Although historically coppicing has been done at different heights, a convincing explanation of which was not found by the authors (I was once told it was to protect the new shoots from rabbits and other grazing animals), cutting right down to the ground is the best practice, some say with a slant from the centre of the stool outwards.

Hazel is usually coppiced for clear rods, but here at Wisley they also coppice birch as a sustainable
alternative to bamboo canes (which are imported all the way from China), which can be woven into rather decorative plant supports. Birch coppices for  sticks are shorter lived than hazel, as, at 20 or so, mature birch develops a droopy habit. Birch cycle is similar to hazel though, at 7-9 years.

While I've not seen the birch coppice myself, I did order two bundles of birch to support sweetpeas and Apios americana in the Cottage Garden, but had never woven it together. Therefore, I was delighted to be given the opportunity to develop the skill, when I was asked to come up with a suitable design (and implementation) of broad bean support for the vegetable garden.

Support no 1

I drew inspiration from a structure that had been in the Cottage Garden last year, to support raspberry canes, and between myself and Mario we came up with an structure that would be functional. It took me a whole morning to build the first one, but Mario was satisfied and I was rather proud.

Support no 2

One week later, it took me slightly less, at 3 hours, to build the second one.

Made braver by the pleasant results, I have now started making a tepee for my Apios in the Cottage Garden too.

It is a rather satisfying job, with a very tangible outcome!

Tuesday 21 April 2015

It's because of the dry spell!

Today I've been pruning Prunus (plums and cherries) for the first time since I've been here.

To be precise, Prunus avium, or cherry trees, and P. domestica, the plums.

To be even more precise, the plants I'm referring to here are P. avium 'Sunburst', P. domestica 'Opal' and 'Blue Tit' ; and this last was flowering beautifully.

You don't normally prune Prunus when it's actually flowering, no - you either do it before or after, and that is generally for light formative pruning. That's what I had to confirm to the dozens of visitors that rightfully wondered what I was up to!

Branch removed as oozing gum is one sign of bacterial canker

But this is indeed a good time of the year for pruning plums and cherries. And the fact we have been having a dry spell makes it a particularly valuable time for pruning, because Prunus are prone to fungal diseases such as silverleaf (Chondrostereum purpureum) and bacterial cankers (Pseudomonas syringae), which are promoted by humidity.

The best time for pruning Prunus, would be indeed a good August, a dry one, that is. But, as always in gardening, there is the best practice, and there are very real constraints, that require compromising for the second best: for example August is one of the busiest time of the year in a veg and fruit garden, while early April may be quieter, so one may actually get down to do what should be done for the health and productivity of the plant.

Our fruit specialist teaching with P. avium

So, after some training by our specialist, I started on the Cottage Garden trees that needed a haircut, mostly a quick one, to give a pyramid shape and keep the height in check, so that cherries can be covered, for example (as that's the only way to save the fruits from birds) and picking is easier.

The principles being that you take big chunks, cutting back to a suitable branch (I was told in cherries you can sometimes leave stumps, much in the way of a Dutch cut but longer, to stimulate new growth): you cut back any new stems that are too long to 30 cm if they are leaders and some 20 cm if laterals. Keeping in as much flowers as possible is useful. Taking out any dead and diseased material to start with.

Acid cherries (P. cerasus) are slightly different in their growing habit, as they flower better on one year old wood, which (if left unmanaged for more than one year) causes long stems with flowers only at the top, that need replacement pruning to try and keep the shape compact.

But I did spend quite a while thinning out and taking some height out of the 'Blue Tit' tree, hence the opportunity for so many visitors to spot me on the ladder.

I am pretty satisfied with the result, there is a lot more air going through the plant, which should help with fungal diseases too. There are still a lot of flowers on, and the shape is pleasant from all sides.

Plum 'Blue Tit' before Plum 'Blue Tit' after

It seems a pity to throw away beautiful cherry blossom, the visitors pointed that out, but we did not waste it: we put the flowers in vases in the messroom to cheer us up, and I got some spare for the student accomodation too.

To prove it, here's me, once I got there, posing as "cherry blossom girl", in a picture I sent as a joke to my husband, as he likes a song by that name... he may have enjoyed the flowers a little bit too! ;p

Monday 20 April 2015

Indoors trained vines - part 2: spring

... go to part part 1: winter

Buds breaking on a spur

As I was saying, now that's spring, I have spent a couple of days training the new shoots, born out of the embryonic buds, to the wires that will help bear the weight of their large and perfect-looking grapes.

How can I impress into the minds of my readers the amount of grace needed to carry out this task? I have been rather terrified myself, but my colleague is in charge of the vines loves this task, and she is very graceful indeed.

Shoot training is a morning task. Because in the afternoon the shoots are more prone to snapping.

Chosen shoot and reserves

One of the shoots that have grown on the spurs is chosen
for training. Generally, it's the vigorous one that is already pointing in the direction it has to grow, parallel to a wire. But sometimes you cannot find one, as they are all growing vertically upwards, for example.

There is a perfect stage for this shoot to be tied to the wire, and that' s when the stem has toughened up a little and does not bend readily under the touch. You then take a narrow strip of wet rafia and tie it, with a figure of eight tie, trying to nudge it towards a horizontal position.

Shoot training is every morning's task. In fact, next morning you come in and check your ties? Has any shoot snapped? If not, you encourage it a little bit further towards the horizontal wire. If they have snapped, and likely wilted, you mourn a little while, then you move on to choose another shoot to train. That is why no shoot that have grown on the spur are removed at this stage. Also, some of them may develop into a nice replacement spur, if they grow closer to the rod and in the right direction.

Grapes grow fast, and at all different speeds. When I did this job 10 days ago, there was only one vine that had sufficiently developed shoots for tying: grape 'Nero'. Today, they were all more or less out, with 'Nero' almost having reached the end of its allotted space, halfway towards the next vine, or about 60 cm.

Vitis 'Nero' on 9th AprilVitis 'Nero' on 20th April
V. 'Lady Downe's Seedling'
They all have a different way of growing, with some putting out solitary minute glabrous inflorescences on slender peduncles and others, like 'Lady Downe's Seedling', pushing large, bunched downy panicles through.
V. 'Sultana': bleeding of snapped shoot

Others are terribly prone to snapping, like grape 'Sultana'.

Today, as the stage of development of the plants is further ahead, besides tying in new suitable shoots and nudging forward already tied ones, we were going to:
Leaf axil: sublateral forming
  • snip off any developing sublaterals from the leaf axils
  • snip off any tendrils (as they have a habit to attach in inconvenient places)
  • snip off any inflorescences in excess of one, that were growing further from the rod (depending whether the closes inflorescence was good enough to develop successfully into the perfect bunch of grapes, of course).
Two inflorescences and tendrils
One inflorescence and both tendrils removed

Two observations from today: one struck me for its beauty, and that is the guttation on grapevines, on young stems and the underside of leaves, and even where a shoot snapped, some bleeding, like a chrystal tear drop.

Snapped shoot with bleedingGuttation
The other one is not very pleasant, as the scales are out in force despite the peeling. I squashed them, but the vines might undergo spraying soon.

Brown scale (Parthenolecanium corni)
Note: the University of California has a leaflet with plenty of pictures for identification of scale insects.