Tuesday 1 May 2018

Transition period

If you sow lots of plants in trays and modules to germinate indoors as I do then it is important to harden them off before finally planting out in their final positions. This is particularly important for tender plants and crops such as half hardy annuals or outdoor tomatoes. It also applies to hardy plants too. Just because a plant, say a cabbage, is hardy, if it has been accustomed to the warmth of a green house then it will still experience a shock, and a check to its growth, if planted out without a transition period. 

This is where a cold frame comes in handy. Of course they are not absolutely essential. You can put seedlings outside on warm sunny days and bring them back in at night. This can get a bit awkward if warm sunny days are few and far between as is currently the case. 

A cold frame is a useful intermediate step from the green house or window sill. Further regulation is possible by how much the 'lights' are open. Tomorrow we are expecting a fall in temperature and a return of heavy rain so I’ll keep some of the cold frames shut.

This spring the weather has been somewhat unpredictable. Having been teased by a couple of  days in the mid 20 Cs a week or two ago, it has since been unseasonably cold. As a result, like our local farmers, I’m a bit behind with vegetable production and there is a growing queue of young plants ready to be potted on or planted out, but conditions have not made it safe to do so yet. 

This led me to decide to build another cold frame to add to the one I already have to accommodate seedlings and young plants. I had enough left over materials from previous projects to do the job except for some hinges. It took me an afternoon to build and measures 16’ x 2’, which is the length of the green house along one side of which it sits.

Cold frame made from leftover bits. The four doors or
'lights' are made from some PVC roofing sheets
Plenty to fill it in one go


  1. It's going to take you several minutes to plant that lot out!

  2. Planting out is the best bit! A lot of the seedlings are for the cutting garden. As always there’s more than I need.

  3. Love the frame Philip. You should sell them. Could use it for cuttings if you shaded the plastic or glass? It's getting too hot for cuttings in the polytunnel.

  4. The greenhouse gets too hot when the sun is out for seed trays and modules too unless they can be watered three times a day.