Propagating Seeds - Lighting - Newbie

[pds2008]

Afternoon all

I have moved to a new house with a proper garden and this is my first spring/growing season. I am ready to germinate some seeds in pots and keep them somewhere light and warm for a few weeks (I have a sun room for that purpose). Do I need to apply any additional light source to the seeds to aid germination? I have watched a couple of YouTube videos that suggest I need to do this.

Any advice appreciated


Yell

[UncleIan]

Afternoon all

I have moved to a new house with a proper garden and this is my first spring/growing season. I am ready to germinate some seeds in pots and keep them somewhere light and warm for a few weeks (I have a sun room for that purpose). Do I need to apply any additional light source to the seeds to aid germination? I have watched a couple of YouTube videos that suggest I need to do this.

Unhelpfully, it depends. On the seeds. On the ambient light. On the direction your windows face.

We've had no problems germinating seeds on a south facing windowsill in covered seed trays. But we haven't picked anything particularly tricky, courgettes, cosmos, sunflowers, verbena, that sort of thing. Cottage garden type stuff.

We did have a windowsill heated propagator, but haven't used it for a while, not seen any dramatic difference, though there well may be specific seeds that recommend it to heat the compost up to warmer than it would normally be.

What you have to watch out for, and I suppose lights might help here, is the seedlings getting leggy, or bending to one side to get to the light, when they're on a windowsill. We fix that by turning them regularly, pinching out, and putting them outside when it's nice out.

[bungeejumper]

The short answer is that you don't generally need auxiliary lighting unless you're growing (ahem) exotic plants for the production of illegal substances - in which case it will be critical to your cashflow. That said, strawberry hothouses and Dutch tomato growers also use lighting, and so I imagine do commercial growers who are trying to get their plug plants into the shops by Easter, several weeks before everyone else's are ready.

But those are special cases, and I'm going to assume that you are not trying to pull off either of these fancy tricks. There is a lot to be said for using heated propagators, but they do come with a risk of over-extended, light-starved seedling plants if you let them get hot when what they really want is light. Which is where you came in, of course?

There is a kind of natural commonsense to sowing most seeds, and it can be a folly to sow them too early if you can't be sure of following through with enough seasonal light. Just follow the timing recommendations on the packet and you'll be fine.

FWIW, we do engage in a bit of early-season forcing, and we have to watch our light levels accordingly. Our three heated propagators have been running at full capacity since the middle of January. (Although we have now pulled the plugs on two of them for the aforementioned reason.) My chillis and my earliest tomato varieties are already eight inches high, which suits me nicely because they need a long season. (Most plants don't.) My melons and my pumpkins are thriving, and my sweet peas germinated at the speed of, well, light, and now they're out on an unheated upstairs windowledge while they slow down and grow stronger.

But these are unusual plants, as plants go, and your average standard plant seeds will do perfectly well, especially at this time of year. Just keep an eye on them and be prepared to find a lighter spot if you see leggy seedings. (Or simply move the leggy ones to the front of the propagator so that they get the best of what light's available.) As a rule of thumb, I reckon to shift any seedling into a pricked-out pot by the time it's three inches high, maybe less. At which point it'll be more than ready to grow without extra heat, so an old metal tray beside a window will be as good as any fancy propagator.

Afterthought: Save the clear plastic trays from supermarket veg, and they'll work well as mini-propagators for your plant pots. Some people swear by tying a clear plastic bag over a pot to force germination, but I've had damping problems and mildew doing that. It takes all sorts.

BJ

[Breelander]

...Do I need to apply any additional light source to the seeds to aid germination?...

Unhelpfully, it depends. On the seeds. On the ambient light. On the direction your windows face....

Some seeds need light to trigger germination, others will only germinate in the dark. As a general rule of thumb (with some exceptions) the smaller the seed the more likely it is to need the light in order to germinate.

A prime example of this is the field poppy. The seeds are like dust and can lie dormant buried in the ground for up to a century. But once the ground is disturbed and they are brought to the surface the light triggers germination, to which the fields of Flanders bore witness after the First World War.

Once growing, any plant needs light. A sign there is insufficient is that they grow tall and thin, desperately trying to grow towards the light source. I currently have tomato seedlings on my windowsill. I have found that a reflective sheet of aluminium foil behind them is sufficient to reflect enough of the window light for them to grow well.