The first time you see your tomatoes popping up in their planting containers, your heart will swell with pride and your victory cries may frighten the neighbors. Then reality hits.
Throw your seeds out on the ground, and they’ll grow. Plant your seeds in individual pots, months before they would germinate in the great outdoors, and they require care. Every day, often two or three times a day, you’ll find yourself back at the potting bench as you thin out seedlings, water, fertilize, open vents, turn on heaters, and other daily chores. I’m not saying this to scare you.
Starting plants from seed is one of gardening’s most rewarding experiences. However, it requires time. Before you plan your dream greenhouse, break out your calendar or to do list and create a seedling tending schedule. Include pre-planting cleanup, planting days, and daily care. Keep in mind that the more plants you start, the more time they need. When you’re planning, if you notice that your schedule is overcrowded, scale back.
Instead of starting three dozen coleus, a dozen tomatoes, another dozen peppers, six squash plants, eight cucumbers, lettuce, and 142 onions — all from seed — start a few lettuce plants, the tomatoes, and the coleus. Flowers are ridiculously expensive.
Scaling back means understanding that cucumbers grow just as well in the ground. Unless you require an early harvest for the market, there is little benefit to the starting of plants like squash, cucumbers, watermelon, and corn. Some plants like carrots are just not suited for transplantation.
Keep Startup Expenses Down
For centuries, our ancestors grew tomatoes without grow lights, temperature mats, or chemical fertilizers. They didn’t have HVAC systems, automatic irrigation, or any of the other bells and whistles one finds in a modern-day greenhouse. Their tomatoes still grew.
We forget this when we’re trolling through gardening magazines and drooling over the latest greenhouse technology. This truth bears repeating. Despite what you may read on University websites and in growing magazines, you do not need a $50,000 greenhouse to start your own plants.
My greenhouse is an old lean-to shed with reclaimed sliding doors along one side and a see-through, corrugated roof. My heating system is a string of rope lights and an old refrigerator thermometer. Grow lights aren’t hanging over my tomatoes either.
Would I like a beautiful glass greenhouse, instead of my eyesore? Absolutely. However, my basic set up suits my needs and keeps my mother’s ferns green throughout the winter. My tomatoes aren’t as stocky as the nurseries, but my chosen variety’s vigor and disease resistance mean my plants outperform ones from my local nursery.
Having a greenhouse means balancing needs and wants. You want an automated vent fan. You need ventilation. Walk out to the greenhouse and open the door or a vent.
Construction Tip: Install a screen door. This will keep weed seeds and pests out and let you use your largest opening for ventilation.
Before you reach for the nearest greenhouse catalog, consider your needs and investigate alternative construction methods. With ingenuity and reclaimed materials, you can build a greenhouse on the cheap.
Don’t get caught up in the hype that surrounds new greenhouse tech. Don’t think that you must have the latest tables and trays. Don’t believe that all greenhouses must have electricity. Do investigate sunken greenhouses, solar heating — both hydronic and air — and traditional ways to store and release heat. Speaking as a lifelong resident of the deep South, getting the heat out of your greenhouse is sometimes just as important as keeping it in.
If you plan on using trays and pots, build these expenses into your greenhouse budget. Reusing pots may spread diseases to your seedlings. If your market grower, include replacing your trays and pots in your annual budget.
Hotbeds and Cold Frames
Hotbeds and cold frames are older technologies that you may find in a Victorian garden. These are boxes with window mounted on a hinge that are placed on the ground. They stand somewhere between knee and waist height and slant towards the sun.
Hotbeds, as the name implies, have a heat source. A century ago, this was an active compost pile. Today, most use heating cable, an electrically powered heat source. You can also heat these with hydronic solar heat. Temporary hotbeds may use heat mats or even rope lights.
Cold frames do not have a heat source.
Although some plans call for uninsulated wood sides, others suggest burying a portion of the cold frame, so the earth insulates your plants, or using foam board insulation or straw bales.
For more information about constructing hotbeds and cold frames, see
Before sowing your seeds, you should clean and disinfect your greenhouse.
This is not just an annual task. Our greenhouses can easily become a breeding ground for pathogens that will destroy our crops, often before transplanting them. Every time an irrigation nozzle, shovel, or planting tray touches the ground, it should be disinfected with a 10% bleach solution before using it again.
- Sweep out any plant debris or other physical remainders of last year’s crops.
- Get rid of any weeds underneath your benches and the along the edges of your greenhouse. Although your greenhouse looks like an indoor environment, these weeds can attract the same damaging insects you’ll find outdoors. They can also cart in diseases such as tomatoes spotted wilt virus and infect your crops.
- Check the screens over your greenhouse vents for tears. These screens help prevent weed seeds from floating in.
- Apply a weed block fabric to your floors; this will help keep them from rooting. It also provides a clean appearance. This is particularly important if you live in an area with poisonous snakes. Anything that lets you see the snake before you tick it off is a good thing. Roundup and horticultural vinegar are other weed control options, but they work best after you have a weed problem, not before.
- Take a shop vac to the floors if you have concrete.
- Consider pressure washing your greenhouse with soap and water. In a more commercial setting, you may also want to look into using a chemical that dissolves algae and hard water deposits.
- When watching the greenhouse, start at the top and work your way down. You may want to wear a Tyvek suit with a hood. This will keep your hair dry, sort of, and also help protect your skin from in any chemicals that you may be using. If you’re using anything other than soap and water, follow all of the manufacturer safety precautions, including wearing a respirator and gloves rated for the chemical that you will be handling. Please note that nitrile gloves and latex gloves like what you buy at the drugstore protect you from biological contaminants, not chemicals. Some chemicals will dissolve them. As in, they dissolve on your hand and adhere the glove to your skin along with the chemicals you are trying to keep off.
Choosing Your Potting System
Every grower has a preferred potting system and soil mix. Some prefer plastic trays and pots. Others like biodegradable pots, including manufactured peat pots and ones made out of newspaper. Still, others drunk Elliott Coleman’s Kool-Aid and fell in love with soil blocks. (I’m a block lover.) Each system has its pros and cons. In general, plastic pots and manufactured biodegradable pots are more expensive long-term than DIY newspaper pots and soil blocks. However, the new plastic pots you purchase this year will likely not infect your tomato crop. Your soil block maker can.
Below is a brief overview of each system, along with their pros and cons.
Soil blocks are the adult version of mud pies crossed with sand castles. You put together your block mix, which may or may not include actual garden soil. Wet it until has a consistency a little drier than your favorite brownie recipe. Then you take your block maker and plunge it into the mix a few times. This packs the material into the block maker. Afterward, pop them out.
Your block maker does not need to be a fancy machine that creates perfectly formed blocks every time. I have one. I love it, but I made my first block maker out of an old tea tin and a few scraps of wood. Other DIY options include cheese dip containers and tin cans.
Potting on soil blocks is simpler than potting on plants grown in plastic pots. You make a larger soil block with a hole the same size as the smaller one. Then pick up your plant, block and all, and place it in the hole. It’s kind of like Russian nesting dolls.
Here are 7 Soil Block Mix Recipes. My current favorite is the large block recipe from Ladbrooke.
- Low cost. Whether you build your own block maker or purchase a system, you will use the same equipment every season and every year.
- Reduced waste. Since block systems use dirt in place of pots, there’s nothing to throw away after transplanting.
- Less transplant shock. When you transplant a soil block, you don’t remove a pot. This means you disturb the roots less.
- Sterilizing equipment. Block makers have a lot of nooks and crannies. Sterilizing them requires soaking them in a solution. Over time, this may damage plastic and metal parts.
- No ready-made potting mixes. Soil blocks use peat moss to glue themselves together. Commercial mixes typically do not have enough peat. They may also contain twigs and other debris that will clog your block maker.
- Dirt makes gardening fun, but soil blocks take this to another level. Expect mud on your elbows and behind your ears.
- If you’re working in an unheated greenhouse during January, you may want to invest in some elbow length rubber gloves. Otherwise, you’ll be plunging your hands into wet, icy block mix for days.
- Not easily available. You won’t find soil block makers at your local garden center. If you want one, you’ll have to order it or make it yourself.
By pots, I’m referring mainly to plastic pots and trays and manufactured biodegradable pots. Although newspaper pots are a fun project, especially if you have kids, manufacturing them is time-consuming. In general, newspaper pots are unsuitable if you plan on starting more than 100 plants.
- No sterilization required.
- Easy to find. Walk into any hardware or seed store, ask them for potting supplies, and they’ll likely point you to a pallet of plastic pots and trays.
- Call up your local extension office, asked them about starting seeds, and this is the system they will recommend. Since most gardeners and farmers understand pots, it’s easy to find help when something goes wrong.
- More equipment. Market farmers, who need to automate portions of their transplanting process, should seriously consider using a manufactured pot system. Most soil block automation equipment is manufactured and used in Europe. Importing it is often prohibitively expensive, and you probably won’t find it used locally.
- More expensive.
- Plastic pots only have one destination: the landfill.
- Increased risk of transplant shock. Plastic pots must be removed, which may damage your plant’s
A few years ago while prepping my fall garden, I tilled over that year’s tomato bed. About halfway through, I stopped to clean off the tines and found the remains of a biodegradable pot stuck between two of them. The pot was mostly intact. After almost four months in the ground, it showed little sign of breaking down. I now question whether these pots are a good choice for my garden.
Pasteurizing Potting Soil
Although some prolific growers, including Mr. Coleman, swear that you don’t need to sterilize your potting soil, my experience suggests otherwise. Even when I use a soilless block mix, I sometimes experience problems with diseases and weeds that I don’t when I use pasteurized mix.
Never heat treat perlite! Add perlite to your potting mix after pasteurizing it, not before.
Pasteurize small amounts of potting mix using your oven. Set the temperature to 200° F. Bring the soil to a temperature of 160° F to 180° F for a period of 30 minutes. The University of Illinois also has instructions for using a pressure canner.
For larger volumes, consider using solarization or steam.
Other Tips and Tricks
A few other random things I’ve learned:
- Damp toothpicks pick up small seeds better than fingers. Simply place the toothpick tip where you want the seed deposited, press it against the dirt, and spin it with your fingers.
- Although 55-gallon drums filled with waters will cut down on your heating bill, copperheads like them, too!
- Use IFTTT to send you a reminder when the temperature will drop below freezing. Here’s my favorite method.
- Sifting block mix with hardware cloth is easier than unclogging the block maker.
- You can make temporary cold frames with foam board insulation, duck tape, and a sheet of plastic.
- Placing grow lights too close to your plants will fry your seedlings.
- When one seedling damps off, others follow.
- Test your seeds before you plant!
Now, grab your potting mix and a few packages of seeds and have fun!
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