Okay, you have your first greenhouse and ready to grow some plants. Here is a list of items you need to be aware of before starting. A simple mistake early on will most likely carry on until the plants, if still living, leave the greenhouse.
It is important to use media that is sterile and made specially for growing in a greenhouse. There are many, including myself, that blend their own but I do not recommend doing this until you have a few seasons behind you. You should use caution using bagged potting soil because many brands use a herbicide to prevent weed growth which will hinder your seeds from germinating. Bagged potting soil is okay if you’re using it for containers with established seedlings but never use for germinating seeds.
You should never bring garden soil into the greenhouse. Garden soil is rich but contains pathogens that could spread and kill off all your plants. You need to remember the environment isn’t the same as outside and a greenhouse often has cool damp conditions early on that could be the perfect storm for damping off. Once you encounter damping off, you must sterilize your entire greenhouse by washing everything with a bleach solution. You must remember that seedlings are fragile and need a sterile environment to survive.
If you plan to reuse containers you need to wash everything with soap and water and soak in a bleach solution for a day before rinsing and letting them dry before going to storage. Again, cleaning planters are essential to preventing disease from entering your greenhouse. The perfect scenario would be to use new containers each year. I do not reuse trays are flat inserts anymore as I have learned my lesson years ago.
Starting seeds in the greenhouse in the early months is a difficult task. The temperature swings from 90 degrees on a sunny day and you will struggle to maintain a consistent temperature at night. Even with the use of heat pads I don’t recommend attempting to start seeds in the greenhouse. I have a heated grow bench in my basement that keeps a consistent temperature and provides ideal growing conditions for germination. Any sunny place inside your home will work but some seeds need light to germinate and using a plant light will increase your success.
There is a fine line between providing the right amount of water and over watering. It’s best to keep your plants on the dry side but remember a bright sunny day can easily fry them. Also, if you use hot air heat they can dry out at night. You should only water in the morning and if it’s a cloudy day avoid watering. When plants are small I use a small water bottle with small holes drilled in the cap. Seedlings need to be kept moist at first but not wet. Over watering will not encourage plants to grow roots and soil born disease to spread.
Perhaps the biggest mistake made from the beginner is not realizing how important ventilation is. Even on a cold day, fresh air must enter, and fans are needed to move air around. It could be hard to find the balance of temperature control and proper ventilation but it is the difference between success and failure. I find it is better to have good ventilation than a warmer temperature. I have better luck leaving windows open on a cold sunny day then trying to keep it warm to encourage plant growth. If your greenhouse has condensation on the inside, you don’t have enough ventilation for your plants. Again, I cannot stress enough that it is better if your greenhouse is 50 degrees with the window open than 90 degrees with it closed.
Once the plants are out of the greenhouse, it is essential to clean your greenhouse before the summer heat sets in. I also make sure everything I stored in the greenhouse is clean. Good housekeeping is essential to your success.
Growing plants in first couple of years in the greenhouse was tough. If it could happen it did and everything I discussed in this article happened to me. At one point I figured I could buy nicer plants cheaper then grow them. But once you get successful your return on investment works in your favor. Not only can you grow plants you cannot find in the store, the joy of starting your gardening season in January is worth every penny.