Medwyn Williams on growing on onion seedlings
Good artificial lighting and support is essential at this time of year
In mid-November I sowed my large onions in the heated greenhouse. This seed’s from Peter Glazebrook’s world record-winning stock and it has now germinated well and will soon be straightening up from the crook stage. The crook stage is when the young seedling leaf has popped out of the compost and is growing at approximately 90 degrees to the upright stem.
I switched on the T5 lights above the seedlings at the beginning of December. I have these on wires, lowered to about 25cm (10in) above the seed trays. The beauty of T5 lights is you can actually get them very close to the plants as there is minimum heat from the tubes and they won’t burn the young seedlings.
I’ll move the seedlings into small 60-cell seed trays in a week or so. I much prefer to have them initially in small cells as they seem to keep themselves upright, whereas in a 7.5cm (3in) pot they have a tendency to lean over. They seem to thrive in these cells as their roots touch the sides quickly and the plants stand bolt upright.
They won’t be long in these cells before being moved into 9cm (3½in) pots using Humax Original Compost. As far as I’m concerned, this is the best compost on the market as it contains silver sand as well as NutriMate.
As soon as the onion seedlings are potted up, I’ll put them back under the lights after re-adjusting them to suit the plants. Another really important job to do is to support the young seedlings to maintain upright growth. I use plastic plant support clips that attach to split canes, to form a complete rigid circle.
One job that I need to do this week is to remove all the weeds from my celery bed, dig out all the soil and wheelbarrow it into the far end of my large polytunnel. This soil is beautiful and rich because I added some well-rotted horse manure during early spring. I let it dry out then use it in my potting mixes next year.