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The Benefits of a Germination Room for Early Seed Growth

By: Jillian Thompson

After finding the cucumber seeds I planted only three days ago had grown more than an inch high, I was motivated to know what factors led to them thriving in our germination room. It seems obvious that moisture, oxygen, temperature and light are all important, but there's a balance in creating an environment where seeds flourish. Different seeds require different environments, so it's helpful to know these facts before you plant.

Kenny, an intern living on the farm, is passionate about compost. He made a moist, fibrous mix that we've been adding to our starter soil. Without the right soil, nothing will grow. Also the soil type, seed depth and compression seem to be important factors, and of course water and grow lights.

I found an online newsletter, Floret, Flower Farm, that was a wealth of information. One article recommends washing the trays before reusing them to prevent the spread of disease. We currently use small cell containers in our germination room for our seedlings. We set them in flat drainage trays. For these specific trays, the media (soil and compost) should be fine with smaller particles, and the soil can be packed down to reduce gaps. Using the compost mixture and soil mentioned above, for the cucumbers, I intuitively planted the seeds closer to the top, which was good, and added a layer of soil and then pressed down. I read that cell trays, which can dry out more quickly under grow lights, should be checked more often, and watered carefully, and the soil should be tighter, not fluffy.

What to consider when planting in a germination room?

Moisture: Seeds from a packet are kept at a 4 to 12% moisture, but when planted this level need to be increased to 25 to 50%. That’s huge! Seeds also have different temperatures that are best for germination, so know your plants! Mist systems are a great way to control the amount of moisture that’s dispersed over the trays and cells. But, it's still recommended to feel the soil. It should be be moist but not soggy. I discovered maintaining proper moisture levels in seedling flats is easier in many ways than in plug trays, which have individual cells that dry out faster. However, we reused several plug trays for our seeds, so checking on the seedlings daily is important. I've noticed they do dry quickly, so we have created a checklist for watering.

Oxygen: A decrease in oxygen can be as simple as planting a seed to deep. The seed requires energy to grow, and can use up oxygen during this process. Overwatering can decrease the level of oxygen for the plant too. A hard seed shell can prevent water and oxygen from getting through, so for these seeds soaking can help soften them before planting.


We moved our ECO germination room last January to the front of the barn, which is a smaller room than what we used last year, and easier to heat. There are several racks with fluorescent lights, a large window, and we keep the room plenty warm - about 75 degrees. It feels like a sauna sometimes!


Our set-up is similar to what’s recommended. We use horizontal lamps with cool light. T8 bulbs are more cost effective, but some growers are even using LEDs. As the plants get more hardy, you can take them away from the light, and allow them to adjust to natural sunlight near a window, which will reduced heat and increase tolerance.

By learning about the delicate balance between moisture, oxygen, temperature, and light, I have more confidence planting and growing seedlings now, and a new respect for germination rooms. Being a successful gardener includes knowing how to create that perfect environment, how to make adjustments, and knowing when plants are ready to survive outdoors where Mother Nature is harder to control.


  1. Title: Greenhouse & Floriculture: Germination Chamber/Growth Room for Seedling Production | Center for Agriculture, Food, and the Environment at UMass Amherst. Website title:UMass Extension. URL: Date accessed:March 11, 2024

  1. Title:Seed Propagation Environment. Website title:Greenhouse Management. URL: Date accessed:March 11, 2024

  1. Title:Great Plant Escape - Germination. Website title:Illinois Extension. URL: Date accessed:March 11, 2024

  2. Title:Seed-starting Basics. Website title:Floret Flowers. URL: Date published:February 20, 2019. Date accessed:March 11, 2024


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