• Briana Bosch

keys for a small greenhouse

One of the questions I hear often is about GREENHOUSES! Because they are a big expense, many people ask me if I've found it necessary and what kind of equipment I use in mine! So here's the overview of what I find essential.

We are in Colorado, Zone 6A (though our field performs closer to a 5B with its microclimate, which skews cold). Therefore, we can get temperatures to -10, so seed starting in a garage is not an option. Our first year on the farm, I started all of my seeds in my basement HVAC room. It's a totally windowless, too-warm room, but I was still able to grow 750 seedlings out of there--with a lot of supplemental lighting, ventilation, and bringing seeds in/out of the house for sunlight! However, with the massive expansion we are doing this year (tripling our flower growing space), we needed to do something different. So, we decided to purchase a glass greenhouse to give us a space for starting all of our seedlings. Here's some of the must-haves I use in mine!

Tools: Soil blockers, nail clippers, toothpick, pen, spatula

  • Soil blockers: I have a 3/4" blocker for most of my seeds (zinnias, snapdragons, stock, celosia, etc.) and a 2" for potting up if necessary and for my larger seeds like sweet peas.

  • Toothpicks: I use this for starting my small seeds. Moisten with your tongue and pick up one seed at a time. Works like a charm!

  • Nail clippers: For seeds that need stratification (gentle nicking to aid in germination) or for thinning seedlings with precision.

  • Spatula: Used to mix dirt, scrape off soil blockers, or transfer small soil blocks if needed.

  • Pens: I have to mark my seed trays AS SOON AS I plant them! Otherwise I totally forget. Because I have two kids and my brain is about to explode.

  • Fertilizer: I dilute Dr. Earth's Pure Gold to 1/4 strength to fertilize my seedlings weekly. I keep it in the greenhouse so I don't forget!

Temperature control: The most important part of a greenhouse is maintaining the temperature! Though greenhouses help regulate temperature, you still need to help out a bit! To avoid it getting too hot, we installed automatic vent openers that automatically open when the greenhouse gets above a temperature that you can adjust. A fan set in a doorway can also help keep it from getting excessively warm and help circulate air, which is good for seedlings.

To help keep the greenhouse warm at night, you have to use a heater in colder zones (of course, this also depends on what you're trying to grow, but I would always recommend having a heater for backup even in warm climates). I use a Dr. Infrared Greenhouse Heater; greenhouse-specific heaters are rated for the high humidity in the air and have more powerful fans to help circulate the air. However, I have a regular ceramic space heater (like one you would use in a home) that I keep as an emergency backup--the last thing you want is to have a heater failure and lose your whole greenhouse, and I have had to use it once when my primary heater stopped working. I've plugged it into a temperature regulating outlet, so I can dictate what temperature the heater kicks on at. Alternatively, you can purchase a heater with a built-in temperature regulator like this one.

Domes: plastic domes help maintain moisture within your seed starting trays. This is important so those little seed trays don't dry out!

Heat mats: Germinating on a heat mat helps ensure even germination, which is important when you're using domes so that they all germinate at about the same time and you can remove the dome to avoid fungus and disease in your seedlings. I use these.

Lights: I use standard 4' shop lights. You really don't need special grow lights, just keep them nice and close to the seedlings (mine are about 2" from the top of my seedlings!).

Shelves: Metal baker's racks from Lowe's or Home Depot leave plenty of space for seed trays and the hanging lights and are adjustable.

Seed Starting Mix: I keep all my seed starting equipment in my greenhouse, along with a stool and table so I can just seed everything right there.

I soil block at the farm, because it helps me reduce my plastic waste and conserves space. I use a mix of about 30% of this Jiffy Organic Seed Starting Mix and 70% the Vermont Compost Company's Fort Vee Mix, which is composed of "a blend of composted manure and plant materials, blonde horticultural grade sphagnum peat moss, crushed and screened granite and basalt, blood meal, kelp meal, steamed bone meal, mined gypsum, vermiculite (a mica mineral expanded by fire), washed coconut coir, herbs (biodynamic preparations)." I find this mix makes for the best soil blocks, full of nutrients, easy to compact, and consistent.

Vermiculite: I dust the tops of all my blocks with horticultural vermiculite, which helps prevent algae growth and also helps maintain moisture for surface-sown seedlings. I keep it close by and just sprinkle it with my fingers over everything I start.

Seed Trays: In the vein of trying to reduce our waste at the farm, I soil block. However, you can choose to use individual cell seed trays. I save my foam meat trays from the grocer and use those for starting our soil blocks. I keep those next to me on my seed starting bench so I can just grab one and go!

Last but not least...

ELECTRICITY: Be sure you account for all the lights, heaters, and seed mats! They don't take a lot of energy when there's just one, but if you put a lot of them together it can blow a fuse or create a fire hazard, so be sure you plan a dedicated breaker for your greenhouse (or at least close access to several outlets)!

I hope this info helped somewhat! If you have any questions, ask away!


2440 Iris Street

Lakewood, CO 80215

(720) 319-0243


© 2020 Blossom & Branch Farm

  • Black Facebook Icon
  • Black Instagram Icon