Before planting your potatoes in the container
you need to decide if you will "earth up" or not as they grow. To
earth up the potatoes is simply planting them in compost and when
the foliage appears above soil level you cover it with more compost.
This process is repeated until the compost reaches just below the
rim of the container.
WHEN TO PLANT POTATOES IN CONTAINERS
The key factor in deciding when to plant potatoes in
containers is the date of the last frost in your area. The
other factor to take into account is that you are growing
potatoes in containers and you can move your containers to a
frost free position if a frost threatens. But you don't want
to plant the potato seed so early that you are moving the
potatoes in and out of cover every other day.
It's a fine
balance between risk and effort against the opportunity to
have potatoes in containers earlier than those grown in the
open. So we recommend you estimate your last frost date (for
example it's 5th May in Birmingham) and
plant your seed potatoes five weeks before that date (which
will be late March in Birmingham). For
two weeks after planting, the foliage will still be below soil
level leaving you with a frost risk period of about three
weeks.
Click
here for what to do if a late frost threatens to
damage your potato plants.
For example, the last average frost date in Birmingham
(about average for the UK) is around 5th May. When we say
"average last frost date" it means that a frost is
statistically likely after that date in only one year out of
seven. Using the above calculations of planting out potato
seed five weeks before the last frost date we would plant
out our potato seed towards the end of March.
Your last frost date depends entirely on where you are in
the UK. Also be aware that frosts can vary considerably over
very small distances. So take advice from more experienced
neighbours in your area if you are not sure of your last
likely frost date.
BENEFITS OF EARTHING UP POTATOES IN CONTAINERS First, earthing up is only feasible if the container you
are using is 60cm (2ft) high or more. Any less and it's best
not to earth up. Also, it's not worth doing with first early
potatoes (their growth is too fast) only with maincrop and
second early potatoes. When you do earth up potatoes, the
main stem becomes extended and the potato plant will grow
more potatoes from this extended stem. Your crop of potatoes
will be larger if you earth up and also fewer potatoes will
be green.
VIDEO SHOWING HOW TO PLANT POTATOES IN CONTAINERS
PLANTING POTATOES IN CONTAINERS
If you plan to earth up your potatoes then you
need to fill your container to roughly one third
full with general purpose potting compost. For a
container 60cm (2ft) high by 30cm (1ft) in diameter
place two or three seed potatoes on top of the
compost with the eyes or the sprouts (if you have
chitted your
potatoes) uppermost. In some cases there may be
eyes or sprouts on both sides (see left).
In that case, position the potatoes so that the majority
of the eyes / sprouts are pointing upwards.
Gently firm the seed potatoes into the compost
being carful not to break off the sprouts and cover
with a further 10cm of compost so that the seed
potatoes are well under the surface of the compost.
We will explain how to earth up the potatoes in the
next page
of this article. If the sides of your container are
flexible then roll them down to just above the level
of the compost (see right)
This will ensure that the sunlight can reach the foliage
as soon as it pokes through the compost. It will also assist
natural rainwater to land on the compost surface and be
absorbed.
If you don't plan to earth up your potatoes then fill the
container to about 20cm (8in) from the top of the container
and place your seed potatoes on the compost surface as
described above. Fill the remainder of the pot with compost
over the seed potatoes to within 3cm of the top of the
container.
In either case, scatter a handful or two of blood, fish
and bone (bonemeal will also do well) on the surface of the
compost and lightly work it in with your hands. This can be
done in a few days time if you do not have this fertiliser
available at the moment. Blood, fish and bone or bonemeal
are long lasting fertilisers which will feed the potatoes
over a long period of time.
If the compost is dry, water the container well. Until
the foliage starts to emerge above the compost you can
position the container wherever you want. Anywhere warm is
best, but not critical. However, if a frost is likely, move
the container to place where frost can't get to it. Don't
forget to label the container with the potato variety and
the date planted.
Depending on the variety of potato and the weather
conditions, you should start to see foliage poking its way
through the compost in about ten days time. Keep a watch for
this because as soon as it happens the container must be
placed in a position that receives the maximum light (if it
not already in that position).
NEXT STEPS
Soon after the foliage of your potato appears above the soil
it will be time to start the earthing up process and general
care. Click that link below (or the "next potato page" at
the bottom of the page. If you want to skip to another
subject in this series click on one of the links below.
