michael adams wrote:

"compo" wrote in message
...

Driving north past Invergordon the other day I noticed that a potato
field which was in full leaf last week is now devoid of leaf. The
haulms have been cut off just above soil level. This prompts me to ask:

1. Why would this have been done


...

The haulms are removed before any possible infestation by blight
which would then travel down to the tubers.

Whether blight takes hold will be directly related to the amount
of foliage there is, leaf and stalks etc for it to settle in.

In combination with the localised humidity.

...


2. How does this affect the tubers beneath the soil (Does it stop them
developing?)


...

I presume you mean does it stop them increasing in size ?

Whether it does or not, the growers will presumably make a
calculation as to whethet they have more to gain by removing
the haulms and all chances of the crop getting blight, than
they're likely to lose from any continued bulking of the
tubers by that stage. The other aspect of potato developemnt
the thickening of the skin which is necessary for satisfactory
storage has either already occured or is independent of the
haulms.

They will probably have this down to a fine art, and will take
account of local weather conditions and forecasts - humidity
especially, when deciding on the exact date.

They may possibly have used sulphuric acid for this. There are
plenty of references on Google regarding the specifics.
Presumably this will also totally remove a possible host for
the blight in the form of the removed haulms.

michael adams
Another reason is they are removed when the potatoes are the size the
supermarket requires, they don't want them too large, customers complain!