Do you pre-spout your seed potatoes?
Are your window ledges covered with egg cartons full of seed potatoes? Why do we bother? Do you produce more resilient potato plants if you don't chit them? I have been doing a bit of digging.
Pre-spouting seed potatoes. I hadn’t really thought much about this and I, like most other gardeners, religiously chit my potatoes in February and March. So why do we chit potatoes and is this still the best advice in light of a changing climate?
Gardening wisdom states that chitting potatoes helps them to get off to a good start, so you get higher yields more quickly. That’s either more tubers, or fewer but bigger tubers.
I did a bit of digging, looking at research papers, some from as long ago as the late 1940s. And the results were rather muddled. Some studies found that chitting boosted yield. Others found chitting produced faster early growth, but fewer stems and tubers. Some found chitting resulted in less scab. The results varied between varieties and between years. In one study, the use of small seed potatoes produced tubers with a higher starch content which suffered from less blight, whereas the use of large seed potatoes resulted in faster initial growth, but the weight of hulms and roots declined more rapidly in autumn resulting to fewer tubers. A study from 1948 showed that if tubers were planted after 11 April – there was less yield and the benefits of manure and fertiliser were reduced. But, overall it was a very confused picture and the results varied between earlies and main crop, and between varieties.
However, there was one interesting paper from 2008 looking at the effects of pre-sprouting, planting date, plant population on late blight and yield of organic potatoes. One benefit that came through from these studies - an early start meant the plants got away quickly and they could achieve an acceptable marketable yield before the onset of late blight, as both pre-spouting and early planting led to earlier tuber bulking in a shortened growing season.
But the results were so dependent on the weather which affected the length of growing season and the timing of the arrival of blight. If the season was blight-free, non-chitted seed and later-planted seed could out yield chitted seed. You can read this paper here
Is chitting still necessary?
I don’t know! The start to this year has been mild and wet and the ground is going to be moist for some weeks to come. If the season continues to be as wet as last summer, then chitting is wise. But think back to 2022, the dry weather meant there was very little blight around and the key issue was heat and water.
Chitting tends to reduce the number of stems produced per tuber and this in turn affects the microclimate of the canopy. A plant with many stems and lots of leaves creates a microclimate that is humid which favours fungal spores. But in a dry summer, a dense canopy of leaves that trap the water could be an advantage.
So, as our summer weather becomes warmer and drier, the chances of a bad blight year decline, so we may be better not chitting and opting for a slower start to let the plant establish a better root system and grow more stems.
A fast start from chitting won’t really help my Sarpo Mira either. Being an indeterminate variety, it grows into the autumn and tubers are left in the ground until required. A slow start would have little impact on this potato (see newsletter 7 Feb).
Do we want more yield?
A strange question to ask perhaps. Most gardeners will say yes, but actually I think we don’t. In times when environmental conditions are challenging, we want crops that can cope with drought, waterlogging, and disease etc. However, a plant that is bred for yield is greedy. We plant potatoes in rich soil and feed them, either with artificially fertilisers or organic mulches, and the resulting fast growth may not produce as resilient a plant as one that is growing more slowly.
What do you think?
First earlies
The ground is still cold, so my first earlies are going in pots. First batch of Rocket are in a pot of the willow compost I discussed last week.
Are you growing first earlies?
Love to hear your views on this!
Talks and Workshops with Kim and Sally
Talk 14 March Sally is talking about climate change gardening hosted by Wells Garden Club, venue Wells Town Hall, Somerset
Talk 20 March Lavington Garden Club, Wilts Sally is giving at talk on the Healthy Garden. There is also a seed swap.
Workshop 24 March Introduction to growing fruit and vegetables with Sally at her garden at Empire Farm in Somerset
Workshop 5 April Growing polytunnel and undercover edibles over winter with Kim from her garden in West Wales
Talk 15 April Sally is speaking to Fagus Garden Club, Nailsea
Workshop 19 April Get climate change savvy GYO course with Kim from her garden in West Wales
Sally’s new book, The Resilient Garden and Allotment Handbook is out 21 March. You can pre-order here
'A must-read for anyone who wants to know how to grow their own zero-food miles, pesticide-free veg, while treading gently upon our planet.' Dave Goulson, author of The Garden Jungle and Silent Earth
Happy Gardening
Sally