How to grow bedding plants from seed in a greenhouse?
Greenhouse seed starting requires balancing moisture, temperature, and light perfectly. Here are my key tips after many successes and failures:
Invest in a soil thermometer - soil temperature is more important than air temperature for germination. Most seeds need 65-75°F soil. Use a spray bottle for watering tiny seeds initially to avoid displacement.
Thin seedlings early - it's hard to do but crucial for strong plants. I use small scissors to snip extras rather than pulling. Transplant to larger containers once they have 2-3 sets of true leaves, holding by leaves not stems.
Watch for "damping off" fungus - if seedlings collapse at soil level, you have it. Improve air circulation and don't overwater. A small fan helps tremendously.
Keep a gardening journal with dates, varieties, and what worked. You'll thank yourself next year! The satisfaction of planting out beds with plants you started yourself is amazing.
As a market grower who starts thousands of bedding plants each spring, here's my commercial approach:
We start with clean everything - sterilized trays, fresh potting mix each year, and clean greenhouse surfaces. Disease prevention starts before you even plant seeds! We use plug trays rather than open flats - better root development and easier transplanting.
Temperature zones in the greenhouse make a huge difference. We have a warm zone (70-75°F) for germination, then move trays to cooler area (60-65°F) once sprouted. This produces sturdier plants.
The key most home gardeners miss: air circulation! We use horizontal airflow fans 24/7 to strengthen stems and prevent fungal issues. Also, we fertilize with diluted liquid fertilizer once true leaves appear - the seed starting mix has very little nutrition.
Label everything clearly and keep records of what works each year. It's a learning process but so satisfying!
Hey there! I'm just a home gardener with a small greenhouse, but I've learned a lot through trial and error. Here's what works in my 8x10 greenhouse:
I start with the easy ones first - marigolds, zinnias, and sunflowers are practically foolproof. Then move to more challenging stuff like petunias and lobelia. I use recycled containers but always wash them well with bleach solution first.
The game-changer for me was getting a thermostat-controlled exhaust fan. Greenhouses can cook seedlings quickly on sunny days, even when it's cold outside. I also use shade cloth during brightest hours to prevent scorching.
My cheap trick: I make my own potting mix with 1/3 peat, 1/3 vermiculite, and 1/3 compost. Works great and saves money. I also use diluted fish emulsion fertilizer once they have their first true leaves.
The best part is sharing extra seedlings with neighbors - they think I'm some gardening wizard!
Starting bedding plants from seed in a greenhouse is incredibly rewarding and saves money! I've been doing this for 15+ years and here's my system:
Timing is everything - most annuals need 6-8 weeks from seed to planting out. Check seed packets for specific timing relative to your last frost date. Use sterile seed starting mix - never garden soil, which harbors diseases. Sow seeds at depth recommended on packet (some need light to germinate).
Bottom watering prevents disturbance and fungal issues. Heat mats under trays dramatically improve germination for warm-season plants like marigolds, zinnias, and petunias. Once germinated, provide plenty of light - supplemental lighting prevents leggy seedlings.
Harden off gradually before transplanting outside - even greenhouse-grown plants need acclimation to direct sun and wind.
The Johnny's Selected Seeds Greenhouse Guide has excellent timing charts!