Starting Seeds Indoors Under Lights

February 8th, 2010 by David LaFerney Leave a reply »
seedlings growing under lights

Seedlings growing under lights

I started some seeds today in my “plant work room” and I thought you might be interested.  I start seeds in regular plastic nursery trays that I get from a local greenhouse – and that I save from store-bought plants.  I do recycle my plant containers from year to year –  If you reuse containers like this you really should wash them thoroughly in a weak bleach solution and dry them in the sun before storing them away for reuse.  Or so I’ve heard – I might try that some day.

just planted flat

just planted flat

This year I’m planting in commercial soil mix, because I just don’t have any compost that is ready right now to make into home made potting soil.  Anyway, fill your containers with soil and plant your seeds at the  recommended depth.  Most of what I planted today is in the cabbage family, and needs to be about 1/2 inch deep.  I just use a finger to poke holes about that deep, drop 2-3 seeds into each one and then sprinkle with more soil to cover.  I’m using pretty small divisions – 72 plants per tray – because I plan to plant out these cold season plants under row covers or in the greenhouse as soon as they are big enough to handle.  If I thought that I would have to hold them for a while I would probably start them in larger divisions to begin with.

BTW, I am also test germinating some seeds that I saved last year – by planting 10 seeds per container to see how many come up.  Assuming that some of them germinate I can just multiply the number of seedlings by 10 to get the success rate as a percentage.  Other than using 10 seeds per container they are done exactly the same way as everything else.

watering a flat with a spray bottle

Using a spray bottle to water the planted trays gives good control.

I’ve found that the least messy way for me to water trays is by misting with a spray bottle – every other method that I’ve used results in muddy water running everywhere and only a little soaking in.  Check soil moisture every day until you’re sure that it has stabilized where you want it – moist, but not dripping wet.

Note that you need to label your trays – I use recycled pieces of plastic mini blinds.

plastic seed starting chamber

A plastic seed starting chamber like this is very handy, but not absolutely required.  You will have to remove it soon after your plants emerge, but until then it helps to keep the soil evenly moist and the air warm and humid.  If you don’t have one of these just lay a sheet of plastic right on top until you see plants starting to emerge.

Then cover with one of these plastic domes if you have one.  If you don’t have one of these you can simply drape a piece of saran wrap over the tray, but if you do that you will have to remove it as soon as you see plants emerging from the soil.  The cover holds the moisture in so that you shouldn’t have to water again until it’s removed.

the grow light setup

My simple grow light setup uses regular 4′ shop lights and bulbs – not expensive “grow” lights.

I use plain old 40 watt flourescent shop lights to start my plants indoors and it works great.  As you can see the fixtures are just sitting on top of props that I have made out of one by six scraps, but you can use whatever you have.  You want the lights to be as close to the plant trays as is practical or your plants will grow tall and leggy.   Now that compact florescent lights are widely available you could also use those in any lamp fixture that you have.  You can easily get CFLs which are equivalent to  a 100 watt incandescent light  – should be great for a smaller operation.

Last year I built a very simple bottom heat system which has made a tremendous improvement in my success rate for starting all kinds of seeds.   If you don’t have bottom heat, then try to keep the soil as warm as possible 24 hours a day.  On top of a refrigerator or an upright freezer is a good place or on a shelf right over your water heater or a heat appliance.  The regular average room temperature of your house is probably not warm enough for best results.  The lights also won’t really work to keep the soil warm because they won’t be on 24 hours a day.  If you look at this planting soil temperature chart you will see that most plants want the soil temp to be around 80 degrees Fahrenheit for best germination.  If at all possible use some form of bottom heat.

light timer

A simple analog light timer is all y0u need for starting your own plants, but you need one that is big enough to handle the load of all of the lights that you are going to plug into it.

For good results you must have a timer to control your lights.  Erratic lighting or 24 hour day lengths will be bad for many plants.  Be sure that you use a timer which is rated high enough for the total wattage of lights that you will be using.   Set the on period to correspond with or extend the  actual  daylight hours – in other words don’t try to have your plants day and night be opposite of the real day and night otherwise ambient light will interrupt their sleep just like it would yours.  I set mine to go on at sunrise and off at about 8 PM.  I currently have the day length set for about 13 1/2 hours, but when I start planting tomatoes and peppers in a few weeks I will increase that to about 16 hours of light per day.

Once I start this process every winter I love to get out in the plant room to visit and check on my plants.  The warm moist air and the smell of clean soil and growing things along with the sun light coming through the windows really takes the edge off of winter for me.  That and a cup of coffee is a great way to start the day.   Round up some seeds and soil, and see if it doesn’t lift your spirits as well.

My plant room

My humble plant work room.  Really just a small well insulated room on the side of my garage with 4 windows, and a concrete floor that I don’t have to worry about getting dirty.  The light bench is sitting on top of 5 steel barrels full of water for thermal mass which help to moderate the temperature.  You can see the rope light that powers my bottom heat there at the lower right.  On the far end of the bench I have just enough counter space to pot things up.  I love it.


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