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Chitting (sometimes known as sprouting) potatoes is one of those practices handed down through the generations that appears to encapsulate the mysteries of gardening. It's one of the jobs that gardeners will do without question but when you ask them why they do it - most of them won't have an answer.
Compared to the potatoes natural habitat of 'sub-tropical' South America, the English climate isn't perhaps the first place you would think to grow these staple crops, but with centuries of selective breeding the modern potato now does very well in our soils. There is one problem that still remains and that is our comparatively short growing season, and this is where the art of chitting potatoes comes in.
While our soil temperature remain below about 10 degrees Celsius not much will happen as the potato - a modified storage organ - is in a state of natural dormancy. Left to their own devices, by the time the soil has warmed up sufficiently to break the dormancy period and begin the new season growth, the majority of potato plants won't be ready to crop until the late summer or even autumn.
The reality of this growth cycle means that we need to 'force' the seed potatoes into growth artificially by introducing light and heat - normally provided by a warm, well lit room. This stimulates the production of new shoots and kick starts the potato out of it normal dormancy. This will also reduce the time until cropping from anywhere between 1 and 2 months.
There are other advantages to breaking the dormancy by chittings as modern early cultivars will crop far earlier and more heavily. You can help the process further by rubbing off all but the four strongest sprouts so that the tuber's energy is diverted into a few really strong shoots that will form the new potatoes as early as possible. Second early and maincrop potatoes also benefit from chitting but they don't need a thinning out of the sprouts. Chitting late cropping varieties will result in them producing their foliage earlier and hopefully produce new potatoes before being hit with infections of potato blight or problems with summer droughts. Again, they will mature earlier and can be gathered before slugs do too much damage the tubers.
You can buy seed potatoes from as early as January but it is probably better to wait until the beginning or middle of February before you begin chitting potatoes. Put the seed potatoes into a box where they can be supported in an upright position - cardboard egg boxes are ideal for this – and place them indoors into a light and airy position. During this time they will require a cool temperature of a little over 10 degrees Celsius. Position them so that the end which has the most eyes (dormant sprouts) are uppermost and the 'stalk' end where they were severed from the parent plant is at the bottom. The new sprouts will form in a couple of weeks and - as mentioned before - its good practice to remove the weaker sprouts leaving four of the strongest to continue. As a general rule of thumb it will normally take about six weeks to chit a batch of potatoes.
If the weather is unsuitable at the time of planting then you can remove all of the sprouts and start again. Also, if you have positioned some of your potatoes upside down, and the potatoes sprout from the wrong end, simply rub off the sprouts and turn the potato the right way up. Keep them where they are while the shoots are developing and they can stay there until they are ready for planting later on in March.
For related articles click onto:
How to Break Dormancy in Seeds
How to Control Slug Damage on Potato Tubers
How to Grow Potatoes
How to Grow Potatoes
How to Grow Potatoes in Pots or Containers
How to Grow Sweet Potatoes in Pots or Containers
How to Plant Potatoes?
When are Potatoes ready for Harvest?
When to Harvest Potatoes
Why and How to Chit Potatoes