2nd year growing seeds using growlight

Hi,
I have bought a 15watt spot light and need some advice on what to do. this is my second year growing plants from seeds. last year i started a little late.
i have planted snap dragons, petunias, tomatoes and sweetpea.
i have planted some petunia in a separate tray and put my grow light above them. does anyone know if this will make a difference. how high abve my seeds should my light be? i figuered there was no point trying with tomatoes as the seeds have to be covered with composs so I am guessing they dont need light right yet! i got excited today.....tommrrow i am going to get a mini green house and get organised. last year i use my porch but my other half will not be impressed if i do it againthis year....something to do with wood and humidity!
any advice would be appreciapted
nattasha

 

Get a little fan to keep the air moving around the plants under the light, they can be a bit weak ant stretchy without some movemnt to toughen them up, it will also help with any potential fungal issues.

 

Hi Natash and welcome to the forum.

I have been growing seedlings and cuttings under lights for a while. My set up is three 30 watt tubes (ie 90 watts) over a growbag tray (ie 4 ordinary seed trays). This seems to work well. I have sown seeds in October and had them flowering just after Christmas.

On that basis your lamp is just about OK for a single large seed tray. If you try to cover a larger area the light level will be too low to have a significant effect. Also, my lights are in a box with white sides to reflect the light back, so anything that you can do to prevent light being lost will be a benefit.

Its worth putting the light on a time switch for say 14 hours a day. 24 hours would be too much. People lower lights to as close as 2 inches of the tops of the plants, to prevent light being lost. In your case I would lower the light till it covers an area of a seed tray. Higher will be too little light, and lower will be more effective but will cover too small an area.

The seeds themselves generally don't need much light to germinate, but the benefit will come with the seedlings. Seedlings need plenty of light, and tend to get leggy if they don't get enough. I have most of mine on windowsills, but its still not really enough light. Also they grow towards the light and many of mine are constantly leaning at 45 degrees even though I turn the seed trays around each day.

With your light you will encourage seedlings to grow vertically and not get leggy.

 

Good point JWK. I was assuming it was a fluorescent.

Remember that all light bulbs, of say 30 watts, give off roughly the same amount of heat. Irrespective of whether they are tungsten, fluorescent or any other type. A 30 watt tungsten bulb only gives about 3% of its energy out as light, consequently the remaining 97% is given out as heat. Although a fluorescent bulb might be 5 times more efficient, it is still only giving 15% light with the other 85% being heat.

The reason we are not so aware of this is that a 30 watt fluorescent tube will be three feet long and the heat will be released over a much larger surface area that an equivalent tungsten bulb.

 

Although seedlings do not need tonnes of light straight away but as soon as the new shoot protudes from the center of the embrio leaves you may from you need a bit more then 15watts of light to stop the stem from streatching out too much.

I have used a 150watt eco light before and found it perfect for seedings and cuttings. The CFL eco lights do not produce lots of heat so its perfect and only costs around £35 and covers a big area.

Thanks Colins Hydroponic Shop