Leggy Plants from the Propagator

Answered by Harrod Horticultural Posted in Category Propagation

Dear Martin

Last year I raised lots of plants for my unheated greenhouse in my dining room in a propagator and then just potted up in large trays on a wallpaper pasting table in my dining room. Some though got leggy and I think I might try one of those blue peteresqye foil contraptions but I was also wondering about some basal heat. Do you think the coils would be worth a go?


Dear Penny

Many thanks for your message concerning the ‘leggy’ plants you raised last year and how to prevent the same thing happening this time around.  

Unfortunately I don’t think a propagator, heating cables or even a heat mat will make much difference to the growth of your plants. The reason they are growing tall and weak – commonly known as ‘leggy’ - is due to light; or more accurately the light quality and lack of it. Because the days are shorter this time of year and on the few occasions the sun does shine, the intensity of the light is not as it is in the spring and summer, so the plants grow tall and pale as they search for more light to enable them to photosynthesise and grow. It’s a little like what happens when you force rhubarb but nowhere near as extreme!  

Solutions? You can sow your seeds later when the days are slightly longer; you can try and find the sunniest location in the house and move the plants around so they follow the sun, turning them regularly, but the only real way to avoid these spindly specimens is to use a grow light, fitted with a special bulb to provide the correct colour of the light spectrum (the temperature of which is measured in º Kelvin) and mounted above the plants. There are many grow lights and lamps on the market and we supply a very well-regarded model.
I hope this mini-science lesson has helped and is not too heavy going; obviously I don’t want to recommend the wrong products and it’s always good to have a bit of background knowledge before you buy!

Thanks again for your enquiry and please don’t hesitate to contact me should you have any further questions or queries.