Today is National Potato Day, so I thought it would be good to plant our early potatoes in the greenhouse. Swift are often called the ‘earliest early’ because they can be harvested as new potatoes in just 60 days when the weather is warm enough. If all goes according to plan, I should have new potatoes by April.
Normally early potatoes shouldn’t be put in the ground until March or April and need earthing up as soon as the shoots poke through the soil to stop them getting damaged by frost. Once the shoots re-appear again after having been earthed up, they are again at risk of being damaged and I have lost a whole crop of potatoes in the past from a late frost that caught me out, scorching the leaves black. It is worth covering them up with fleece during the night if the weather forecast threatens a frost.
Rule of Thumb for Planting Early Potatoes in the Greenhouse
When planting early potatoes in the greenhouse, the same rules apply but as a general rule of thumb, you can plant them about a month earlier than you would outside. I actually plant mine earlier than this! As soon as there is enough warmth (and we often get a few warm days in February) they will start to grow, if it is too cold they will just sit there. Providing the soil isn’t too wet, they don’t seem to mind.
I planted half of my 2Kg bag and will plant the remaining seed potatoes outside when the weather warms up in March or April. This should provide us with a steady crop of new potatoes until the summer when there shouldn’t be too long to wait for the main crop potatoes. I manured the ground with organic poultry manure (pellets) before planting them to ensure I get a reasonable crop.
- The ground should be well dug and manured before planting.
- Chitting potatoes is beneficial. Rub off all except two shoots as soon as possible to stop excessive growth.
- Potato Blight isn’t normally a problem for earlies. Blight needs two days where the temperature is above 10⁰C and there is humidity above 90%.
- Earthing up potatoes protects them from frost but also stops tubers from seeing the light and turning green (and poisonous).
- Planting early potatoes in the greenhouse usually avoids slug damage.
- Plant seed potatoes 1 foot apart and 6 inches deep.
- Store early potatoes when dry in the dark, they do not keep so use them quickly.
Remember green potatoes should never be eaten since they contain alkaloids which are poisonous.