Should You Chit Potatoes?

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Should You Chit Potatoes? There has been extended debate for many years, over whether to chit seed Potatoes, but there has been very little evidence to support or refute the practice that has been available in the public domain, for the home gardeners.  However, in Academia, it has been a subject of significant amounts of research, which provides a definitive answer to this question. 

The Answer Is….

Yes, Potatoes should be chitted.  Academic studies have demonstrated that chitting will increase the size of your harvest, and reduce the days to harvest.  However, whether you choose to chit or not, you will still get an excellent harvest, as Potatoes are one of the easiest and most productive vegetables to grow in your garden.

What is Chitting Potatoes?

Chitting Potatoes, is when seed Potatoes are exposed to light, in the months leading up to planting in the garden. The exposure to light, encourages the formation of sprouts on the surface of the Potato, prior to them being planted.

How Much Does Chitting Affect The Yield?

In an article published by The Horticultural Research Institute of Ontario (authored by Alan McKeown), the impact of chitting on the yield of 5 varieties of early Potatoes, over a 3 Year period, was studied.  The results presented in the table below, show the average of the 5 varieties tested.

Tonnes per HectareYear 1Year 2Year 3
No Chitting12.86.514.2
Chitted16.57.918.5
% Difference29%21%30%

The results in every year, show at least a 20% improvement in the yield, after 82 days.  Interestingly, the improvement occurs irrespective of how favourable or unfavourable the growing conditions are in a given year.

In this study, only whole seed Potatoes were used, our much smaller trials suggest that further improvements in yield, may be obtained by cutting the seed Potatoes in half, after chitting. For more information, go to https://planyourpatch.com/can-you-cut-seed-potatoes-in-half/.

How Much Earlier Can I Get A Harvest When I Chit Potatoes?

The results from the researchers, also indicate that chitting has a significant impact on the timing of viable harvests, but this impact diminishes over time.  

Tonnes per Hectare Days 68Days 82Days 96
January5.916.931
February5.817.932
March61829
No Chitting0.911.926

The data indicates, that there is a substantial difference after 68 days, suggesting that for a home garden, it would advance the harvest by 2-3 weeks.  Practically for most home gardeners, it means a reduction in the number of plants required to be harvested, early on in the season.  This would mean more Potatoes would remain in the ground, for a longer period, increasing the overall harvest substantially.  The signal to harvest has traditionally been 2-4 weeks, after the appearance of flowers.

If you are considering growing early potatoes and are alittle short on space grow potatoes in bags are an option. Ready made grow kits are available from yougarden.com. The kits in you get 3 grow bags and 3 types of early Potatoes. The other option is to buy the seed potatoes separately which can be done at yougarden.com for those living in the UK and Seeds Now for those living in the US.

Does It Matter How I Chit The Potatoes?

In the study, the seed Potatoes were chitted for different periods of time, to assess the influence on yield.  Seed Potatoes were exposed to light at the start of January, February or March, before being planted out around the 20th of April.  The results obtained are shown below.

Tonnes per HectareYear 1Year 2Year 3
Jan16.98.718.7
Feb16.78.319
March166.617.8
No Chitting12.86.514.2

The data indicates the longer the Potatoes are chitted for, the better the yield.  However, the degree of this effect is relatively small.  This suggests that a period of around 6 weeks, will be sufficient to gain a significant improvement. 

The researchers also looked at the effect of temperature on the Potatoes, and found that Potatoes stored at 2-4°C (35-39°F), tended to produce multiple stems, whereas, those exposed to temperatures around 10°C (50°F), produced a single shoot.  The multi-stem plants yielded higher, which indicates that is preferable to store the Potatoes away from a heated living space. 

The extent of the harvest achieved, will vary depending on the variety. Trials run by the Royal Society of Horticulture in the UK, looked at 20 different early Potato varieties. To read about which varieties performed best, go to https://planyourpatch.com/what-are-the-best-potatoes-to-grow-in-bags/.

What Affect Does Chitting Have On Main Crop Potatoes?

The study discussed in this article, primarily focuses on the commercial advantages of chitting, in terms of timing, as it had a significant affect on the price for early Potatoes. However, if the Potatoes were allowed to mature, it was observed that the difference in the size of harvest reduced between chitted and unchitted Potatoes and it was statistically insignificant.

This result suggests that benefits of chitting main Potato crops, in terms of the overall harvest, is negligible, when the Potatoes have been allowed to fully mature. However, it is beneficial in cases where the Potatoes are harvested before the Potatoes are fully mature.

As such, it remains our view that chitting should be done for all types of Potatoes, as it provides greater flexibility on the timing of the Potatoes harvest.

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