Monday, January 28, 2013

Starting Seeds-In the House or A Greenhouse

To satisfy popular demand I am writing a quick lesson starting seeds and discuss starting in the house or in a greenhouse. 

Owning a greenhouse is not as costly as you would think. For the home gardener there are many portable greenhouses to choose for and one for every budget. When I farmed in NC Don built me a greeenhouse that was a lean to style off the side of our shed/shop building. I showed him a photo in a magazine and he just designed it as he went along, it was 8' x 12'. He finished it in 3 weekends and had we not made a poor choice for roofing it would have cost us $500. It ended up costing $800 but was worth every penny. It held up wonderfully and worked hard for me for five years until we moved. 

NC greenhouse on the right side in this picture.

Here in MA because we are in temporary housing I purchased a portable greenhouse. It is 5'x6' and 6' high. It has a large front door that zips and a zippered flap window on back wall and side flaps that roll up for more air circulation. You have to create shelving inside it but that is easy with cinder blocks and planks of wood or a shelving unit. This one cost me $99 at Home Depot and I consider it one of the best purchases I ever made. 

It was super easy to assemble and made of a sturdy steel pipe frame and a good weight plastic cover. My son put it together for me in about an hour.

Seed Starting 

I have alot of book knowledge on this topic and had a semester long course on just greenhouse production, but I am only going to share my own personal experience framed with the book knowledge about starting seeds. I have never, and I mean never, had one success with starting seeds inside a house in a sunny window.  They get white flies, knats, bacteria, mold, damping off. The first two years I farmed I bought all my seedlings or direct sowed. When I got my greenhouse I had a disastrous first year before I started my horticulture program. I discovered I was letting the greenhouse get way too hot letting the temps go to 90 degrees, thinking the plants liked that. My 1 or 2 inch seedlings would stop growing, and I couldn't figure out why. I fianally called my Ag Agent and he came to visit. When he went into my greenhouse he looked at my tomato seedlings that had been the same size for 2 weeks, and asked "what temps do you keep? " I told him I use the space heater when it drops below 35 and that's all. He smiled and said, "Don't let it go below 50 at night and get a fan and don't let it go above 70 in the day." I was shocked. When I told him the daytime temps he said thats why they are not growing. They have shut down. 

I ran and got an oscillating fan and opened the window and in a week the seedlings had tripled in size. Amazing!  

Greenhouse tomato seedlings getting hardened off outside my NC greenhouse
Last year was my first year farming in MA and using my itzy bitzy portable greenhouse. Here are some photos of the seedlings. 
MA tomato seedlings transplanted into window boxes to get bigger
MA broccoli & cabbage babies

Big MA tomato seedlings

MA broccoli

MA tomato seedlings getting big
Tomato babies in MA greenhouse
So, my sure fire method of starting seeds is to keep the trays evenly moist using the mist setting on a hand held sprayer attached to your hose. Do not let the water puddle, it will cause seed rotting, mold and bacteria. Mold, fungus and bacteria thrive in warm wet environment, that is why mushrooms are grown in dark damp places.  Starting seeds requires, light, moisture, warmth and air circulation. Keeping these things in mind you can easily start seeds that will grow into strong healthy seedlings. 

Always use trays that will drain do not start seeds in huge pots, they like small shallow containers to start out in. I use the flat trays that you can get at garden centers or from many suppliers online. When the seedlings get their third or fourth set of leaves I move them to bigger containers, but still keep them in the greenhouse.

Mist when watering to be gentle on the seeds and seedlings as they will be very fragile when young. 

Keep night temps at 50F and day temps no higher than 75F. I got a small table top space heater that also has a fan setting and oscillates at Walmart for $12.00. It worked perfect in my portable greenhouse set up on the bench so it was at plant level. In my bigger greenhouse in NC I used a floor model of the same type. 
I also got a small tabletop oscillating fan to keep air circulating and for cooling off on sunny days. It may only be 40 or 50 degrees outside in March or April but inside that greenhouse it is easily 80 degrees+. I open one flap window and turn on the fan. On days it could get to be 90+ inside I open the door and window flap and use the fan. 

The seedlings are stimulated and grow stronger stems with a little wind on them. So I keep the fan on during the day  on the lowest speed and keep it oscillating. 

I use an organic seed starting soil and when the seedlings are getting their second set of leaves I gently water them with water soluble seaweed/fish emulsion from my one gallon watering can. That is all the fertilizer they will need until they start setting flower buds (tomato) or when they are transplanted into their permanent beds or spot in the garden. 

That's it. If you follow these steps I can assure you, your seed starting will be as good as a greenhouse professional. In the photo below, see the plants on the left side of the picture? The huge ones, those are the tomato seedlings in the greenhouse photos above from last year. My friends and customers joke that I don't sell tomato plants I sell tomato trees!

Tomato trees
Ok, One more thing to talk about. I realize not everyone wants or can afford to get even a portable greenhouse. For those folks I recommend starting cold frames which can be built inexpensively with wood sides and free windows. It is similar to a greenhouse environment but has the much needed fresh air factor that inside of a house cannot offer. I use a drop light in a cold frame for heat at night rather than a heater and prop the window open slightly for air circulation. 


  1. Once Summer is in full swing I do not use the greenhouse or coldframe any more. Fall crops can be directly sown in Midsummer into the gardens. But I do use the cold frames to grow greens over the winter. I have sort of gotten away from that because now I just put a hoop house over 1 of my raised beds.

  2. I suppose I will bite the bullet and get a portable greenhouse this year. Seed starting indoors is virtually impossible. When do you start your seeds? (I am in MA too.)

    1. You will love having it Maureen. They take you to a whole new level in gardening/farming. I start around March 1-15.