Growing potatoes - frost and other dangers

The rain stopped, the sun came out and all around me at the allotment everyone started getting their potatoes in. At the beginning of March. This seems very early to me - this time last year there was snow on the ground. In the three previous years, we've had frosts in April, in London. Just because we've had next to no frost at all this winter so far, doesn't mean there's none to come. And while potato tubers in the ground are protected against a light frost, the stems and leaves, once they develop, are very vulnerable to even  an air frost as I've discovered to my cost more than once.

Lady Christl potatoes, planted in the third week of March, damaged by frost in April. This plant recovered - 2-3 others were lost completely.

Potatoes (along with tomatoes, now I come to think of it) seem to attract more than their fair share of folklore about the best way to cultivate them. There are people who swear by planting potatoes on Good Friday. This would make more sense if Easter didn't move. This year, I might well plant some potatoes over Easter weekend, but they will be the last lot to go in, the maincrop Pink Fir Apples which won't be harvested until late August. The earlies will be planted around the end of March, weather and temperature permitting, and the ground covered with straw. Any sign of a cold snap coming and the fleece goes on.

Then there's the old canard that growing potatoes in a new bed will break up the uncultivated ground. I've long argued this one. I don't dispute that potatoes can be a good crop to grow in a new bed since the bed will get well and truly dug over (although it's also said that eelworm is more prevalent in uncultivated ground), but to my mind there is nothing magical about the potato itself that breaks up the soil and makes it workable. It's all down to your hard work. First you dig the ground over, then you dig a trench to a depth of six to eight inches, plant the potatoes, cover with soil and possibly some organic matter mixed in, then as the haulms grow, you rake or hoe up the soil to earth them up. No wonder the soil gets broken up.

Earthing up. I sure I read somewhere that Hugh Fearnley-Whittingstall doesn't bother. I get lazy about it too. Covering the stems can protect against late frosts (see above) and keeps the growing tubers in the dark, so that they don't turn green and toxic. But sometimes drawing up the soil can be hard work, especially if it's the first year the bed has been cultivated. Most years, I earth up somewhat perfunctorily to start with and then top up by piling organic matter over the plants: straw, leftover compost, grass cuttings - grass cuttings work particularly well because the lawn starts to need regular mowing at the same time as the potato plants put on a growth spurt. The job is done - stems protected, tubers kept in the dark - and the organic matter then acts as a mulch to enrich the bed for the next crop. 

Using straw to help earth up the potatoes.

I've often been told that you should harvest potatoes once they're in flower. Possibly, if you want potatoes the size of a grape. I've found that external signs - flowering, the plant yellowing and dying down - can be unreliable. Plunging your hand in to check the size of tubers works better for me (and is another reason for not earthing up obsessively), and yes, I usually tentatively try this for the first when the plant is in flower.

Mayan Gold potatoes in flower  - but probably not yet ready for harvesting.

Of course potatoes don't have to be in the open ground at all. You see bespoke potato cultivation sacks for sale in Sunday supplements and garden catalogues, but to me this is another piece of unnecessary advice. If you are going to grow potatoes in a container, a black-lined binbag will do just as well - see here for details.

Charlotte potatoes growing in a black binbag.

Rainbow veg - Orange is for Physalis

Physalis, or Cape Gooseberries, or Inca berries, (Physalis peruviana) taste infinitely better when picked fresh from the plant then when bought from the supermarket. The taste is sweeter and more complex than the fruits imported from, usually, South Africa and stored before going on the shelves.

Although most of our homegrown physalis gets eaten as an allotment snack, my ambition is to get enough fruits to make physalis jam, which I've heard a number of people say is their favourite.

I’ve been growing physalis for two to three years now and discovered that in the UK it needs a loo-o-ong season. The plants actually did better in the cool summer of 2012 (when we had a bright warm spring) than the long warm summer of 2013 (when the temperature didn’t get much above freezing until well into April). This year I’ll be sowing the seeds indoors in early March and will keep them cosseted and warm, transplanting into decent-sized pots before they go outside once all the frosts are done. I’ve also got a new raised bed lined up for them – hopefully they will reward me for this five-star treatment by producing some beautiful golden fruits come October time. 

Sown in pots in March and kept at an even 20 degrees temperature
until ready to be hardened off and planted in a sunny sheltered
spot outside.

Just another Seedy Sunday

Seedy Sunday has come a long way since the first community seed swap event in Kemptown in 2002, but it remains the biggest of the Seedy Sunday events in the UK. This year’s event at Brighton Corn Exchange brought around 3,000 people together to swap seeds, buys seeds and plants, attend talks, including one on organic gardening from Bob Flowerdew himself.

I hadn’t been to a Seedy Sunday since the days when it was held at Hove Town Hall, but its relocation to the Corn Exchange hasn’t, thankfully, been accompanied by any attempt at gentrification. The hall was packed: seed suppliers included Thomas Etty, Beans and Herbs, and Pennard Plants, and then down at the far end of the hall on a large square of tables, visitors rummaged eagerly through the seed swap packets, which remains the heart of the event. No matter how obscure the seeds you’re looking for, there is a good chance you’ll find them at Seedy Sunday, and a guarantee that you’ll be distracted by many others at the same time.

I browsed through the brown paper packets looking specifically for violet tomatillos (found), purple-skinned Violet de Gournay radishes (not found as such, but Thomas Etty has promised to sell me a packet from their stocks back at HQ), and stripey-skinned aubergines (found, Listada di Gandia). 

There is usually a wide variety of seed potatoes, and Pennards were selling the Salad Blues I was looking for, and also had a separate display of soft fruit including pots of All-Gold raspberry canes. A good haul. Last time I visited Seedy Sunday, I bought my first ever wasabi plant and a couple of lemon grasses, but I could find no lemon grass this time.

The distractions were the delightfully named Black Truffle tomato, a mountain pepper plant (Drymis lanceolata) from Edulis Nursery – evergreen, very hardy, leaves and black berries both edible – and a bottle of rosehip syrup, as I completely missed out on making my own last year.

And always on the look-out for space-saving ideas I couldn’t pass by Evergreen Roof Gardens without taking a good look at their modular vertical planting system, below.

Seedy Sunday

Seedy Sunday originated in Canada in the late 1980s, in order to bring communities together to share open-pollinated seeds and heritage varieties. The first Brighton event was in February 2002 and remains the largest Seedy Sunday event in the UK, although there have also been Seedy Sundays in Eastbourne and Cambridge - and a Seedy Saturday in Lewes, in Sussex.

Yet the whole idea of seed swapping and heritage variety exchange is currently under threat from proposed EU legislation, covering the registration of 'plant reproductive material' (seeds, tubers, cuttings, etc). The proposal is grinding its way through various readings and amendments - in its original form it would have made it illegal to swap seed, even between amateur gardeners or on a friendly or neighbourly basis. Campaigning from a number of bodies, including the RHS, Real Seeds and Garden Organic has seen some exemptions for private gardeners added to the proposal, but there is still more to be done to ensure future access to as wide a variety of seeds as possible.

Click here for the full text of the current draft report to see how it might affect you.

Oca - the 'lost crop of the Incas'

These beautiful rose-coloured tubers are oca, or new Zealand yams (Oxalis tuberosa). Once an unusual novelty item, they are now offered by a number of mainstream vegetable suppliers, often promoted as a blight-free substitute for potato. I think it will take more than pretty pink skin to supplant the potato in British gardeners' affections, but I found oca to be a versatile addition to the kitchen garden and  notably trouble-free to grow.

They are also rather romantically known as the Lost Crop of the Incas, and like potatoes, they do indeed hail from South America. The name New Zealand yam was given to them because they have been commercially cultivated in NZ over the last 20-30 years and has nothing to do with their origins.

These are often described as tasting like lemony potatoes. Unlike potatoes, however, they can be eaten raw, with a crisp, crunchy flavour. Cooked, they have a texture not dissimilar to a waxy new potato, but the lemon notes are much more muted. They remind me also of Jerusalem artichokes, though without the flatulent after-effects. They also have another advantage over the Jerusalem artichoke - they don't need peeling.

Suppliers include Real Seeds, which has a number of different varieties available, so you can experiment with red, yellow or pinkish coloured tubers. The site characteristically also has plenty of useful information on how to grow and maintain the crop.

Your oca will arrive as tubers, like potatoes or Jerusalem artichokes, in March. Last year I potted them up and kept them in the frost-free patio greenhouse while I figured out where to grow them on. They should not be planted out in the open ground until after the last frost. I planted my five tubers out in April in a spare row at the bottom of the potato bed, so in a well-drained soil with some organic matter dug in, though they seem to be fairly unfussy in their soil requirements. They don't really need earthing up and quickly grow into a low shaggy bush with shamrock-shaped leaves. A bit of routine weeding and watering in a dry spell should keep them happy.

As the nights draw in during autumn, you start playing a a kind of cat and mouse game with the prospects of frost. Oca plants aren't frost-hardy, but the tubers don't start to swell until the days get significantly shorter in autumn, and need as long as possible to grow to full size. In October I dug up one plant out of curiosity and found nothing. But by the end of November, I found lots of plump little tubers definitely worth harvesting – with a delicious nutty flavour with that hint of citrus.

If you do get a light frost, and assuming that in October/November this won't a be a deep, hard freeze, the tubers can be safely left below ground to swell up further, even though the leaves will wilt and look frostbitten. You can also protect the plants with fleece in order to prolong the season. The blog Growing Oca also has some good oca cultivation tips, especially on managing this end of season period, and keeping the tubers growing.

Finally, you should remember to keep some good-sized specimens back to replant the next spring - no need to keep ordering new tubers every year. Put the saved tubers in a pot somewhere cool but frost-free and cover with dry or just-damp compost.

For even more details on oca, the author at downtheplot.com has been growing oca since 2007 and has shared his experiences on how to maximise oca yields.

Digging up tubers at the end of November.

Rocking roots - the crimson and the white

For some year now I haven’t grown turnips because I’ve been under the impression that I’m the only person in the family that likes them. I think I was given a packet of Bianca Lodigiana turnips (a white variety from Lodi, south of Milan) from Franchi Seeds this year and sowed them in a rather offhand way in a spare bed at the beginning of the season. They repaid me for this neglect by coming up sweet and nutty, round and wonderfully unblemished, all at once of course thanks to my lack of successional sowing. 

It clearly pays to have the soil well-prepared. Turnips are a brassica (Brassica napus), so prefer slightly alkaline conditions in favour of acid. You can either lime the bed beforehand or if you think your soil ph is fairly neutral, use spent mushroom compost as manure. In any case, brassicas tend not to like freshly manured ground, so if you can use a bed which you manured the previous season, this should be ideal for them. In this case, the turnip bed had been used for sweetcorn, beans and squash grown in a three sisters formation, all greedy crops requiring plenty of organic matter. The seeds can be sown in March for a summer crop as I did, or continuously throughout the summer to provide roots through to late autumn and into winter.

Other tips for good turnips include not letting the growing plants dry out at any stage, or else they will become woody, and also being ruthless with thinning the crop at an early stage. I often find it difficult to pull out what look like perfectly healthy seedlings: psychologically it helps if I then eat the thinnings, in a salad, or used as green garnish. Then I feel as though I'm harvesting, rather than wasting good plants on the compost heap.

We picked and ate them when still young - about the size of a satsuma - and snowy white. They were delicately sweet with that slight mustardy tang, and were hugely popular with everyone. The most entrenched turnip sceptics were particularly won over by having the smaller ones glazed whole – cooked with butter and a little sugar as you would for glazed carrots.

Picked young, you also get the benefit of the tops, which can be cooked like spinach for a delicious fresh green. 

Another similar brassica, kohl rabi (Brassica oleracea), did well too. Last year I grew the variety Delicacy Purple, sown in March the same way as for the turnips, and which cropped from July to November from a single sowing – I was pleasantly surprised by how long the season lasted. I've always liked kohl rabi which to me taste like sweet broccoli stems - my favourite part of broccoli! The flesh of the swollen 'bulb' is a pale creamy-green colour, no matter what the colour of the skin.

In theory, kohl rabi can be prepared and eaten like turnips. In practice, mine usually end up in a salad, often with an oriental style hot, sweet dressing. I'm also happy to give them a perfunctory peeling and then munch on the kohl rabi as if it were an apple - and just as refreshing.

2014: The year of the rainbow diet

I think we’re going to be eating a rainbow in 2014. Orange raspberries, scarlet carrots, purple asparagus …

The multi-coloured carrots have been requested by my son who enjoyed enormously our forays into purple carrots a couple of years back. Nowadays we think of carrots as being uniformly orange, but until the 1500s people would have eaten white, yellow or purple carrots. Orange carrots were bred and popularised in Holland to reflect the Dutch national colour, and spread across Europe.

This year I’ve sourced some purple carrots and also a bright red variety, Atomic Red, from Seedaholic in Ireland, as well as some yellow and white ones from Seeds Of Italy. We’ll try to outwit the carrot fly with some companion planting, with fleece and with growing them up high where the carrot fly can’t reach them. In theory, anyway.

I’m planting out a new asparagus bed this year and I’ve heard that the purple varieties are sweeter than green, so have ordered 10 Crimson Pacific crowns from Victoriana Nurseries. I’m not giving up on the green version though, still growing my favourite Connover’s Colossal as well.

I’m buying one year crowns which I’ll plant out in the new bed this spring although they shouldn’t be harvested either this year or next (I bet I won’t be able to resist trying a spear or two next year). So I’ll keep the old bed going as well and won’t dig that over until 2016!

I’m refreshing the raspberry canes as well after ten years. We’ve now got creeping cinquefoil (Potentilla reptans, I think) in the bed which is proving mighty difficult to remove without damaging the existing canes so I have decided to get rid of the dastardly weed as a first priority and replace any canes which have to be sacrificed to the cause. 

I've been looking at multicoloured options here as well: All-Gold raspberries are available from several supplier, as well as the purple Glen Coe, although these are eye-wateringly expensive compared to the red and yellow varieties. 

New Year’s allotment resolutions

Alongside the oft-repeated resolutions to eat more healthily (perhaps, even a tad less), to drink more healthily (and less of the hard stuff), I have a few allotment-related pledges this year. Who's with me?

1. I will sort out the seed box ... instead of finding an empty packet when it comes to sowing time, or assuming I've run out and then discovering I've just bought a duplicate. 

2. I will make more use of seed swaps, bartering with friends, the allotment trading hut ... more interesting varieties often found that way.

3. I will put up a proper squash trellis so that the pumpkins grow upwards instead of sprawling all over the allotment ... then I won't trip over them and I'll be able to mow the grass properly.

Pumpkins being trained upwards rather than outwards.

4. I will not let the weeds get out of control in the asparagus bed ... because it only makes them worse.

5. I will not mind if the quince tree doesn’t set much in the way of fruit this year ... since it is probably exhausted after producing such a glut last autumn.

6. I will clear beds promptly so that I can sow again later in the season ... because in the rush to get new crops planted out I usually let the whole idea of successional sowing slide out of view.