Friday, 21 August 2015

Putting the culture back into horticulture

Breeding for biodiversity and sustainability with the help of the public.
The case of Oxalis tuberosa.
Part of the coursework for my RHS Special Option Certificate in Fruit and Vegetable Cultivation took the form of a dissertation, so I made use of the opportunity to explore a topic that I had at heart.

For the last year I have been supporting the launch of a collaborative breeding project for oca (Oxalis tuberosa) in the UK: the Guild of Oca Breeders. Oca is an Andean crop which starts tuberising when days get shorter at the end of the summer. However, in temperate climates, the underground growth of the tuber is checked by frost, which kills the leaves above the ground. The same happened to the potato when it was first introduced in Europe, before day-neutral varieties were bred. The Guild aims to breed oca, which is a delicious tuber, in the same direction as the potato was. Because breeding is a resource-intensive process, and since there is little or no commercial interest in sponsoring it, the project wants to mobilise the help of voluteers.

As I explored the various aspects of the project, I realised that a great deal of interesting topics had to be touched upon:
  • the relationship between culture and agriculture: people plants and the land; 
  • the breeding requirements for small and sustainable growers: resilient, locally adapted varieties, rather than uniform crops suitable for shipping around the world (which are favoured by "conventional", industrial agriculture)
  • the intricacies and costs related to plant breeding rights and their impact on access to seeds;  
  • issues of financial viability for small breeders and the opportunities from the "citizen science" movement.

With limited time on top of a full time job and plenty of other coursework, I could only scratch the surface, but I think my dissertation works as a very high level introduction to the topics above, referencing some rather interesting articles - so I decided to publish it here.

The table of contents goes as follows:

Putting the culture back into horticulture

  • Edible crops for the future
  • Sustainability, knowledge and culture
  • Biodiversity for resilience
Plant breeding and participatory models
  • Issues with current breeding methods and legislation
  • Breeding for low input and marginal lands
  • Participatory Plant Breeding
  • Citizen science, open source, open data
Oca breeding and the Guild of Oca Breeders
  • Oca a crop for the future
  • Small scale oca breeding
  • The Guild of Oca Breeders

Tuesday, 18 August 2015

PD&D: pests, diseases and disorders

As part of my coursework for the certificate, I had to write a Pest and Disease project. I researched 15 of the most common pests (vertebrates and invertebrates that feed, inhabit or otherwise live off plants, damaging or killing them) and diseases (caused by microorganisms such as fungi, viruses and bacteria), ones that I had the opportunity to see in person at Wisley.

We were not required to study disorders, which usually go together with the other two categories in the acronym "PD&D"; disorders are physiological conditions that cause the plant to behave abnormally, for whatever reason except pest and diseases (i.e. nutrient deficiencies, drought, heat, physical damage etc.) - they are very difficult to identify, as this excellent guide from Michigan State University explains.

One such disorders I encountered at Wisley was on 'Conference' pears. In some years more than others (maybe due to some nutrient deficiency and possibly facilitated by dry weather), some pears develop corky lesions on their skin, which may on occasion be mistaken for fungal disease scab (Venturia pirina) but have been identified as a likely disorder. 'Conference' pears are particularly prone to them: I had it on my tree at home and receveid a good few questions from visitors that spotted it in the Fruit Garden. Dealing with it means simply removing the worst affected fruitlets so they do not take up the plant's energy; most fruit grows out of it to be happy pears anyway.

Disorder, unspecified (badly affected fruitlets, left; mildly affected, right)
Pear scab (Venturia pirina) damage
But back to my project, on pests and diseaseses... knowledge is for sharing, so here it goes:

The table of contents:


Apple (Malus domestica) and pear (Pyrus communis)
Brown rot of apple and pears (Monilinia fructigena, M. laxa)
Apple and pear canker (Neonectria galligena
Apple powdery mildew (Podosphaera leucotricha)
Rosy apple aphid (Dysaphis plantaginea)
Codling moth (Cydia pomonella)
Apple and pear scab (Venturia inaequalis, V. pirina)

Blackcurrant (Ribes nigrum)
Big bud mite (Cecidophyopsis ribis)

Gooseberries (Ribes uva-crispa)
Gooseberry sawfly (Nematus ribesii)

Grapes (Vitis spp)
Grey mould (Botrytis cinerea)

Raspberry (Rubus idaeus)
Raspberry beetle (Byturus tomentosus)
Cane blight (Leptosphaeria coniothyrium)


Cabbage (Brassica oleracea)
Cabbage root fly (Delia radicum)
Mealy cabbage aphid (Brevicoryne brassicae)

Leek (Allium porrum)
Leek rust (Puccinia allii)

Pea (Pisum sativum)
Wood pigeons (Columba palumbus)

Thursday, 30 July 2015

Plum days

I have not written for a while, busy as I was with coursework deadlines, but in the last two days I have spent some time with plum trees which felt worth sharing.

Yesterday I helped the Plant Health and Seeds Inspectorate (PHSI) pick leaves from the orchard for testing for plum pox virus. We picked 24 leaves each from 125 of the 127 trees that constitute the new plum orchard (2 of the trees did not have enough leaves on them to provide a full sample), with gloved hands, changing gloves after every plant to avoid cross-contamination. The leaves were sealed in plastic bags and kept in a cool bag until sent for testing.

Today I was helping our fruit specialist with chip budding plums, something I had been looking for. The process does not look too difficult, but of course it's all in the skill of the practician.

First, one has to collect the bud material: ripe new year wood, often found on the south facing side of a plant.
The stems are trimmed of the leaves, leaving a small part of the petiole (it would be longer for T budding, as it would serve the purpose of a handle). 
They are then labelled and kept in a cool place, preferably wrapped in moist towel until use.

Sometimes one cannot find first year wood, so it is possible to try with second year material.


Toe cut (the "lip" on the left), and buds removed

The buds are removed, one by one, with some 3-4 cm of stem around them: practicing a toe cut at the bottom and then sliding the budding knife from the top of the bud down to the toe cut.

It is then the turn of the rootstock, which has to be previously cleared at the base for 20-30 cm.
Standing astride over the plant,
  • on the north side (so the stem from the bud straightens up by growing towards the sun) of the main stem, 
  • at a height of 10-15 cm to avoid rain splashes (with possible fungal spores) and 
  • possibly above a node (which will stop the knife from sliding accidentally)
one makes another toe cut, then measures the lenght of the bud and cut a similarly sized slice out of the stem. The bud is then slid into the toe cut, ready for binding with grafting tape (a clear plastic strip).
Chip bud with first year budChip bud with second year bud
Binding needs to be tight: the fruit expert reckons that a good bud with bad binding has less likelihood to succeed than a so-so bud with good binding. The buds need to be covered by the tape too, unless it's too big to fit (i.e. on second year wood). The best way to bind is with clear stretchy grafting tape. This is tucked in at the bottom, then wrapped upwards, and closed with a knot, pulling any hanging bits to finish.

Binding over one year old wood budBinding around two year old wood bud

Today I was in charge of the binding, and we went through some 90 rootstocks!

The tape will be on for 4-6 weeks until callusing on the wound is well underway. The fronds of the rootstock will be left on the whole season; cutting back will only take place next year in February (late February for apples), just when the sap start to rise, but before it's too strong, which may "flood" the bud and kill it.

Monday, 18 May 2015

Chelsea Flower Show 2015

Press day at Chelsea Flower Show and the RHS trainees flocked into London to lend a hand while getting some insider's knowledge of the UK's most famous display of plants and garden design.

I was assigned to assist one of the judging committees for the exhibits in the Great Pavillion: on a tight schedule of two and a half hours we had to help the judges navigate their way through 17 exhibits, which they were to judge, according to their expertise.

The displays are judged based on the brief submitted by the designers, and according to horticultural and design criteria such as:
  • plants, 
  • overall impact;
  • endeavour;
so that the best receive a medal: bronze, silver, silver-gilt and gold. Special awards are also assigned to gardens and exhibits during the show.

The judging process is very confidential as the stakes are high for the participants of such a high-profile show, and results are not announced until tomorrow. That is why trainees are asked to help the judges get the space to view the exhibits thoroughly and in comfort, and the privacy to discuss and propose their votes without external pressure. In the process, we got the the opportunity to experience the judging first hand.

As the name reveals, Chelsea is mainly a flower show, but there were some fruit, vegetables and herbs exhibits and I was on the committee in charge of evaluating them, which was fascinating!

The judging viewing completed for the medals, a group of us also helped the judges on a further round of judging sessions for the awards. The judges were then going to spend the rest of the day finalising the distribution of medals and awards, while we got time to spend visiting the Show.

Potatoes at Chelsea!

My favourite edible exhibit was an educational potato display with some 140 varieties: tubers of varied colour and shape, grouped around their on species' plant, on a black background, put together by Morrice and Ann Innes and sponsored by seed and plant company Thompson & Morgan.

For some people, seeing such variety of potatoes must be a novelty indeed... it was for me when I was first invited to join a Facebook group of potato breeders and growers called "Kenosha Potato Project" where I've seen the strangest, more colourful and interesting shaped tubers from across the world and learned that "papas" is the original name of these favourites of tubers. They come as coloured and stragely shaped as below!

The Grenada's ‘Pure Grenada’s Rainforest’exhibit was also rather gorgeous, displaying lush green, bright colours, spices and fruits that are native to the island: one had to recognise tha some places on earth are blessed with particularly show-worthy flora, such a Solanum mammosum or titty fruit that is said to resemble a human nipple to one side and a cow's udder to the other, and pink banana Musa velutina.

Solanum mammosumMusa velutina
Delicious fruits, such as the colourful fruit of Theobroma cacao that gives us chocolate, or Zingiber zerumbet, with edible tubers, juice, leaves that can be used as flavouring and flower heads that provide shampoo!

Pouteria sapota and Theobroma cacao Zingiber zerumbet
I also found a delightful herb garden

Herbs exhibit
where I was particularly attracted by 3 herbs: Galium odoratum edible dainty leaves and white flowers, which I first saw in a garden I worked last year and two non edibles: Polemonium caeruleum with dark leaves and blue flowers and Prostanthera rotundifolia a shrub with pink flowers.

Pennard Plants stand

Detail of vegetables at Pennard's

And I will finally mention the rather glorious exhibit by Pennard Plants, inspired by a R. Kipling's poem"The Glory of the Garden" in its 150th anniversary, with stunning vegetables.

PS: Glad to say the potatoes I helped being judged got a gold medal, the first of its kind! Grenada and Pennard Plants were also gold medallists.

Friday, 15 May 2015

In the veg garden

Sowing sowing everywhere, than thinning out, planting out, covering, watering... nobody is to be left behind, in the rush to get the beds filled and looking lush! That is what I have been doing over the last two months in the veg garden particularly.


To get the perfect sowing, the beds need raking to a fine tilth.

Then, with the help of a row maker, you can draw straight lines at even, well calculated distances, and of course perfect grids (for planting out). 

Rows to sowGrid to plant out
A meter stick is however better for sowing, and in in some planting out circumstances, and, with the occasional help of a trowel, or a bulb planter, over the last month I have sown shallots...

Summer radishes are sown 1-1.5 cm deep, at 1 cm spacing (thinned to 5 cm), with and 20 between rows (15 in a greenhouse); one shouldn't water seedbed until germination. In summer, if the soil is dry, water the drill before sowing the seeds to create a microclimate for them to germinate but not the surrounding soils.
There are two type of summer radishes: rosette leaves (ideal for early sowing, require
lower light levels) for examle 'Rudi', 'Scarlet Globe' and tuft leaves (ie 'French Breakfast') which are  best sown towards the end of March.

If you sow too late they go straight to flower same if you don't thin them out.
Winter radishes you sow beginning of summer to Aug, they are ready Sep to
Nov, some like mooli, also know as daikon, overwinter but require wider spacing, at least 30 cm and 30 cm between rows.

2 March
13 March, thinning out
13 April
30 April


Spinach is sown at 2.5-3 cm, then thinned straight away to 5 cm. Then, depending how big you want your plants, you can harvest one in two plants as baby leaf. 30 cm between rows.

Spinach is very sensitive to day lenght, there are early sowing (flowering on longer days) and late sowing varieties (that can be sown both spring and autumn, as they are flowering on shorter days).

2 March
20 April, thinning out

13 April

Beetroot is for April to June sowing, but a few vaieties that do not bolt if they get cold (ie 'Boltardy') so they can be sown earlier.
Spacing is to 5 cm (seeds are in cluster) and 30 in between rows. They require
thinning of any extra seed in the cluster that germinates by snipping off.

2 March
20 April, thinning out, poor germination

13 April

Carrot 'Marion' is very good for growing all year round even if not the perfect flavour, but aside from that variety there are early maincrop and late carrots.
Carrots seeds are very thin, and difficult to handle. Taking only a small pinch at the time helps sowing at the right distance, which is 1 cm by 30 cm. 
Because of the risk of carrot fly (Psila rosae) attack, carrots are covered at sowing, only uncovered once for thinning out, then covered again until picking. Because of that, you will get one crop all together; however, since the carrot fly is not around in autumn, overwintering carrot can be picked as needed.
19 March
Fleecing the carrots against carrot fly

30 April thinning out, uncovering

Broad beans

Sown in the first week of March, took about a month to germinate
25 May
N.B. A good rule for sowing different crops next to each other: the space between them should be calculated as space of crop 1 + space of crop 2 divided by 2!

Thinning out


I have never practised thinning out before, so this was new learning for me. You have to choose the strongest seedlings that are about the distance you require, and pull out the remaining ones. If you do thin when the seedlings have a well developed root system already (because you are too late) or when you have seeds in cluster (like with beetroot) you have to snip the competitors off rather than pulling them out, so as not to disturb the roots of the ones you want to keep.

Once you have done your thinning, it is best practice to firm the seedlings in in the row, by earthing them up slightly from the sides. Then water them well.

Planting out

Several crops are grown in the propagation facilities and then planted out. All the brassicas and the lettuces for example.

One of the most interesting things I learnt while hear is that some crops like to be planted at the same level they were in the pot, even if they flop when planted (for example brassicas and lettuces). Others need firming, for example celery, which is also planted close together to provide a minimum blanching effect, even though modern varieties are self-blanching and do not need to be earthed up or otherwise be covered.


Brassicas like firm soil around them, and the taller the brassica, the firmer the soil needs to be. Brassicas need cabbage collars to keep the cabbage root fly (Delia radicum) at bay (if kept soil free, they form a dry environment that dessicates any eggs laid on them, while in the process helping to slow down slugs).

Covering is also required from the cabbage white caterpillar (Pieris spp). But brassicas requires a lot of light and netting shades them. So we use netting with large holes, pulled taut so the butterflies cannot squeeze in!

14 April, cauliflowers
13 Apr, cabbages28 April, covered


I did plant quite a lot of lettuce, so I now feel rather confident. It is generally grown in jiffy's here, so- when they are about 10 cm tall, you need to water them well to start with, peel off the ridge of the pot, then plan them at soil level having well loosened the soil for example with a bulb planter, then firm gently. Finish with watering.

13 April20 April
28 Apr

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