Answer: Any type of seed that you can start inside the house can be started inside your greenhouse. There are some plants that are more suitable for greenhouse growing than others, but any seed can be germinated under greenhouse conditions. Depending on the time of year, you may need supplemental lighting to get your plants off to a good start. For example, if you plan to start some seeds in late winter, the days are short and there may not be enough light for good growth. If you start seed in late spring then as long as you have good sun exposure you shouldn't need supplemental light. You'll need to closely monitor the temperature inside the greenhouse. Most are equipped with automatic thermostats that turn on heat or open vents as needed.
Just like indoor seed starting, use a sterile soilless seed starting mix and sterile containers. Plants will need to be monitored for adequate water and fertilizer. There are a number of books pertaining to growing in greenhouses. Try the book "Foolproof Planting" by Rodale Press, ISBN #0-87857-876-5, for some great seed starting tips. Another good book is "Greenhouse Gardener's Companion," by Shane Smith (Fulcrum, 1993).
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