Oca Oxalis tuberosa
One of the Lost Crops of the Incas, Oca tubers are an important staple
in the high Andes, grown amongst potatoes and another gem from
the region, Ulluco. While hardy enough to be grown in Britain,
they are easily cut down by frost and are day-length dependent.
This means that in some years the foliage can be cut down by frost
while the tubers are only half formed. Therefore, without some
frost protection late in the year, yields can be very low. The
last few autumns in Britain have been particularly mild, and a
bumber crop has resulted. So most years they are well worth while
attempting in the UK. In New Zealand they grow particularly well
and are well known there as a root crop.
They have a similar flavour and texture to potatoes, for which they are an
excellent substitute. They are a useful alternative where the traditional pests
and diseases of potatoes -- such as blight and scab -- are a problem. And they
can be eaten by those people who might otherwise be allergic to potatoes.
Start the tubers off as you
would seed potatoes; chit them (that is, encourage the tubers
to sprout) in a cool and light place such as a shed or gararge,
keeping them frost-free -- a windowsill is good. If chitting is
delayed or is not possible, it is not absolutely vital as their
main growth is made after mid-summer. Plant the tubers out when
all risk of frost has passed. There is little to be gained by
planting very early, and we have found no benefit in early planting
under cloche protection. Space about 1 foot apart in rows 2 feet
apart, or equidistantly at 18inches. We like to grow them at this
latter spacing in deep beds, and they are particularly suited
to this method. This spacing might seem excessive compared to
the size of the tubers, but the foliage does become quite extensive.
As the plants develop, they
soon begin to look like giant Wood Sorrel, to which they are related.
It is unnecessary to earth them up as one would potatoes as they
do not become poisonous if they turn green, and the density of
the foliage tends to blanch any which appear on the surface. The
plants are quite neat and tidy in habit. We find that only one
weeding is necessary; after then, the foliage becomes so dense
that further annual weeds get smothered out. Perennials like Creeping
Thistle find their way through, and Bindweed, but then they always
do. Some yellow flowers are sometimes produced later in the year,
but fruits are rarely set.
To harvest, it is important
to wait for as long as possible. You cannot realistically expect
tubers until the end of October at the earliest. You might be
tempted to inspect the plants for tubers forming in late summer,
but usually there is no sign; the tubers seem to grow right at
the last minute, when a full canopy of foliage has been built
up. A light frost will sometimes harm the tips of the foliage,
but leave them a little longer as further growth is often made
if milder weather then follows. Only when the leaves have completely
turned to mush should you dig them up. Insert a fork near the
centre of the plants and lift -- the tubers do not extend out
very far. The colourful tubers are very easy to spot, and should
be detached from the stout rhizomes. Leave them to dry a little
on the soil surface, then store in bags in a cool shed.
To eat, try them raw for maximum
crunchiness. In the high Andes, they leave the tubers out to dry
in the sun for a few days so that they shrivel slightly. Shrivelling
is reported to enhance the sweetness of their flavour, and remove
some of the bitterness. For cooking, treat them exactly like
potatoes. They have no descernible skin, so don't peel them. They
retain some of their crunchiness if they are not overboiled, and
their flavour is enhanced if they are baked or roasted for half
From Future Foods
small independent mail order supplier specialising in rare and unusual edible plants.