Gardening Knowledge


Many thanks to Irish Seed Savers Association for recording and making this valuable piece of gardening knowledge available to us following its publication in their members newsletter. If you want to hear and learn more from him, click here for courses info.

Jim Cronin’s 10 tips for growing blight free potatoes (Talk from Clare Garden Festival 2013  entitled 'Taking the Fright out of Blight') written by Marrianne Cronin (no relation!) of Irish Seed Savers Association

The very knowledgeable Jim Cronin gave two interesting talks at the Clare Garden Festival in Ennis at the end of April.  Both talks were attended by many people who must have gone away with lots of information and enthusiasm for their gardens.  I was lucky enough to catch most of his second talk which he called something like ‘Jim’s 10 steps to avoiding blight in your potatoes’ even though there are more than 10 tips!  Jim mentioned lots of other tips too but space limits what I can fit here.  He started his talk by telling us that the large companies are trying to find that elusive, single variety of potato which will be genetically modified BUT will be immune to blight.  As Jim pointed out though, in his experience over 40 years in horticulture, growers have been trying to control a disease called botrytis.  This is a type of rot which keeps mutating so much so that there are now 27 strains of botrytis, mutating faster than the chemicals that are supposed to be destroying it.  So we should be trying to work with nature because maybe there’s no such thing as beating it!  Jim told us that some of his advice is proven scientifically and some of it he has learned over the years.  So here it is as well as I can remember it, I hope I do it justice…JimCroninTalk

  1. Use a large egg sized seed because this has maximum vitality and gives the best return.
  2. Use a potato with a short purple sprout, avoid planting potatoes with long white stalks as they will be more susceptible to blight.
  3. Chitted, green potatoes are more resistant to blight than small, wrinkly soft potatoes.  Weak shoots and weak stalks are more susceptible to blight.
  4. The soil needs to be fertile, potatoes are like ourselves, if we are run down and tired, we are more likely to come down with a cold.   Always plant your potato into fertile, alluvial soil, free from clumps of clay; you don’t want your potato struggling to come around clumps of soil.
  5. The longer it takes a potato to come above the ground, the more resistant it will be to blight.  While its under the ground its busy sending out many sprouts.  A strong, purple sprout that’s slow to come to the surface will have more blight resistance.
  6. It’s been scientifically proven that sciláns* get blight quicker than whole potatoes; sciláns produce weaker stalks so don’t plant any sciláns.   Needless to say, don’t damage the seed when planting as its more likely to get blight if you bruise it or cut it with the spade.*People cut their seed into smaller pieces called sciláns to get the seed to go further.
  7. When the potato comes up above the ground, keep it weed free  If its gets weedy this reduces the air circulation which in turn leads to spores and disease.  Keep the potato earthed up, the more a leafy  rosette that the stalk makes, the less likely the plant is to get blight. The more you earth it up the less blight you are likely to get; all the time being careful not to hit it with the hoe or shovel.
  8. When the rosette can be covered by an upturned 3 gallon bucket (i.e. the rosette fills the circumference of the bucket), its time to give the plant a feed of liquid seaweed, diluted at 500 to 1. Liquid seaweed contains silica, silica gives brilliant antifungal protection.  Liquid seaweed has nitrogen in it and when you spray this on you will think it works like magic and you think to yourself it would be a good idea to give them another shot but this causes them to grow too quickly.  You will get the same benefit from Horsetail which is in the hedgerow in May, this also contains silica, and so you could make a tea of horsetail and use this. Either of these preparations must be sprayed on in a mist with a sprayer, it’s not sufficient to use the watering can to water either of them onto the plant. The Horsetail that is growing in your garden is the single best Horsetail to use on your potatoes (see a horsetail recipe at the end of this article).
  9. The varieties you choose are also important. Floury potatoes are more likely to get blight. Potatoes with a high resistance to blight are Orla, Home Guard, Remarka (main crop), Setanta, Sarpo Miro, Sarpo Axona. These potatoes have a good resistance to blight and if you follow all of the above tips, you should be able to grow your potatoes without the fear of blight.
  10. Spacing is all important because it allows more air circulation. If you are growing your potatoes in a polytunnel, they should be planted 10x10inch apart. Outdoor first and second earlies should be planted 12x12 inches for early, and outdoor main crop should be planted 24X12 inches, preferably 30X12 inches apart; all the time keeping a weed free crop.
  11. When digging up potatoes in the autumn, if gardeners find a soft one its often chucked into the hedgerow and this can be a carrier of blight for our garden, a ‘volunteer’ who will hang around until next year and pass on the blight.  So don’t throw the potatoes into the hedgerow.
  12. If you smell blight or see the evidence on the leaves of your potato plant, get your secateurs and cut off the stalk leaving enough that the potato can re-sprout and because the potato has an overhead food supply, it will continue to grow, it will continue to double and mature. The other thing is that the new sprout that the potato throws up is more blight resistant.  Give it a slight earthing up and let it develop the new blight resistant stalk: leave it in the ground and away you go.
  13. Rotation is very important, if you grow potatoes in the same ground year in year out, you are going to get blight earlier and earlier every year. In organic growing, we always talk about one year in four, so if you plant potatoes in a particular patch  this year, it would be at least three years or three families before you plant potatoes again in that part of your garden again.

I found this Horse Tail solution on the internet: Collect the whole green plant on a sunny day and spread thinly in an airy shed to dry. The dried plant material can be stored in sacks that can let the air through easily.
To use: Simmer 50g in 2 litres of water for approximately 1hour.
If the fresh plant is used take 200g to the same amount of water. Dilute by 5 times its volume and use the spray as a preventative measure.
Note: Marsh or Wood Horsetail are not as useful for this purpose as common horsetail which differs from them in that the internodes on the main stem are shorter than the lateral shoots.
A simple method is to collect a load of ‘Horsetail’ and put it in a barrel of water. Allow it to break down over time, a couple of weeks, stirring occasionally. Dilute it to a light brown tea colour and spray it on or around the plants.

So happy potato growing and remember the old Irish saying…’It is easy to halve the potato where there is love’

Keep an eye out for next year’s Clare Garden Festival towards the end of April, it’s well worth a trip.



(Again, many many thanks to Marrianne and to Irish Seed Savers - delighted to have this great talk recorded!)