I forgot to mention the tubes are compact tubes about 50cm long U shaped.

Anaman, particular species of plants need to have their seeds sown on the surface of the potting mix because they require light to germinate. Others need to be sown with usually a light sprinkling of potting mix on top of them so they are kept moist at all times (or at least they do not become too dry too quickly). Still others, especially large seeds with tough outer shells need to be planted deeper. In the later case, warmth is especially important. In either case, you should put them directly under the lamps.

I know of no seed that needs darkness to germinate; that would seem counterproductive since the emerging seedling will search for light. But some need a period of cooling (vernalisation) to get them going. For example, my Cleome need to be put in the refrigerator for 24 hours
before sowing to speed-up the germination.

As for the lamps (aka tubes or bulbs), every "spectral power distribution" graph I have seen on the "U" shaped lamps show poor emissions of violet, blue, and red wavelengths - and these are the only ones plants and seeds need. Red wavelengths are particularly important for seed germination. But give it a try and see how it works. I would suggest that you place the seed trays or pots close to the lamps and be careful that they remain moist but not waterlogged. Of course, lower them from the lamps as the plants grow in height as even artificial lighting can burn the newly emerged growth.

John-z thanks for your answer. Yes you are correct if in nature seeds required darkness, once they germinated they would die through lack of light. That makes sense now. I will think more logical about this in future!

I have aubretia seedlings under at the moment although they were not germinated under the lights.They are doing very well indeed. Before I got my light unit they were etiolating at a window, but now standing very erect, and the new sprouters more compact.

John the unit will have an OK spectrum, the lighting unit is a horticultural lighting system, bought from a hydroponics company for the specific purpose of plant propagation.

The tubes are compact 55watt Daylight, 'Super Blue' lights by Osram, similar to Sylvania in the USA so should be fine for the job of raising seedlings until ready to pot up.

The super blue lights have quite a higher blue end spectrum for vegatative growth.

Thank you so much John for your very kind help and information to get me started on what promises to be a great supplement to my plant growing hobby.

John here is a picture of my propagation area.

Here is a link that might be useful:

"U tubes" are typically triphosphor tubes, just like most other modern high-performance fluorescents. They work fine for germinating seed. In fact they work find for all forms of plant lighting. I don't know the exact tube you have but they are likely to be Octrons, typical domestic triphosphor spectrum, high lumen maintenance, good efficiency, long life.

Some seeds do need dark to germinate but not very many. If you blast these seeds with high intensity light they will not germinate. Quite a few seeds need light to germinate but any light will do, it doesn't have to be your full-on intensity. Most seeds don't care much either way. The full light intensity is needed once the leaves appear so that the plants grow strong and compact.

How long you can use the lights will depend on how much light the plants need and how tall they are. At this time of year, plan on getting them into the sun as soon as possible. You could probably grow a tomato plant to maturity under those two lamps (might not flower and fruit very well!), or several half-trays of seedlings to a few inches tall.

Thanks shrubs_n_bulbs for the extra information. At the moment I have some aubretia seedlings under the lights, they are doing very well and developing fast. As soon as they are big enough to handle I will get them out to normal light.I'll then overwinter them in a cold frame.

In the bigger propagator I have some contoneaster horizontalis cuttings which rooted after only about a week. They are almost ready to pot on into 3" pots.

My next batch of cuttings will be Japanese Evergreen azaleas, and also going to try some cuttings of Chaemycyparis obtusa (Hinoki Cypress)and Juniperus chinensis.

Anyhow I sure am having fun, and it will enable me to continue experimenting with seed germination and cuttings over the winter months, when usually there is little to do plant wise.

Thanks again for the help, my next batch of seeds I will not worry about so much, just germinate them and then get them under the lights to grow and develop.

Shrubs_n_bulbs I just noticed your in the UK.

The unit I am using is a "Starlite 2" lighting unit made by Canatronics. The bulbs are Osram 55 watt PLL compact tubes marked....OSRAM 55 W/840 4800 Lumen LUMILUX. The guy in the hydroponics shop described these as 'Super Blues'

I intitally looked at Maxibrite PL2 units but this unit is much superior in build quality.

By the way I have put my seedlings outside for a couple of hours this morning. I will gradually build up the time they are out each day until they are fully hardened.

Gotcha. The Lumilux are pretty good. Don't know the Starlite 2 unit but it looks basically OK. BTW, the 840's are cool white not daylight (there is an 860 daylight bulb), I suspect the hydroponics guy was trying to scam you again, or maybe just didn't know what he was talking about, but they are fine.