A home gardener may choose to grow any number of plants from seed. Two benefits of seed starting, or propagating, are how inexpensive seeds are compared to their already-started or mature counterparts, and the broad variety of plant types you can get as seed but may not find otherwise. This time of year is typically when you should start your seeds if you plan on transplanting them to their permanent locations in the spring. Several methods exist for propagating seeds. You may sow seeds directly into the container or space in which they will grow, or you can start them in one container and transplant them after they have become seedlings. For the purposes of this article, we will focus on seeds that you intend to transplant.
There are a lot of things that will influence your success in starting seeds. Before your purchase your seed, make sure to do some homework. The variety of plant you select will rely on several things like our climate, your planting site, growth habit and size, and any treatments you may need for disease resistance. Once you have your variety selected, make sure to buy quality seed from a reputable dealer in order to ensure it’s the correct variety and free of contaminants like weeds or insects. It is also recommended that you only purchase enough seed for the current season—while you can store seed from year to year, the germination and vigor of the seedlings will decline. If you do have excess seed, store it in a tightly sealed container in low humidity at approximately 40 degrees F. Prior to starting your seeds, review the seed packet for information on when the seeds were packed, how you should plant them (row space, depth) and their expected time to germination.
Once you have your seeds, there are a few materials you will need to start them successfully. Any container can be used to start seeds as long as it has good drainage, is deep enough for root development, and is sanitized prior to use. You can buy commercial containers or make your own. Using a container with a lid is ideal as it stimulates a greenhouse-like environment with high humidity that promotes plant growth. You will also need to consider your growing media. Any sterile, soilless potting media without fertilizer is acceptable for seed starting. Typically, this type of media will be free from weeds and disease, be lightweight, and have good drainage. Avoid using garden soil or anything similar as it is heavy, holds a lot of water, and may contain weeds or other diseases. A DIY mixture might consist of 4 qts shredded sphagnum peat moss, 4 qts fine vermiculite, 1 tbsp superphosphate, and 2 tbps ground limestone. After mixing, wet the mixture thoroughly and leave it to drain for at least 1 week prior to planting. Then, you can plant your seeds at an appropriate depth (reference your seed packet) in the medium. Once you have your container and medium ready, be sure to place it in a warm location with bright, indirect light and good air circulation.
A final few notes on thinning, transplanting, and hardening off to follow. Many times, you will plant several seeds in one space to ensure that you grow the final number you desire. Ultimately, the seedlings will crowd each other and compete for water, light, and nutrients. If you have several seedlings in one spot, remove any small or weak ones by snipping them at the level of the soil. Once your seedlings have developed their first true leaves, they can be transferred into an intermediary container. Create a hole in the media of the new container and using a pencil, gently lift the seedling from the germination container and place it in its new home. Avoid planting the seedlings too deep or shallow, and do not move them by grabbing their stems. When they are ready to move outside, you will need to slow their growth and thicken their cell walls via hardening off. This should be done 1-2 weeks prior to transplanting to the outdoor garden. To harden off your seedlings, move them outside to a shady location, gradually increasing the amount of sunlight they receive and length of time you leave them out. This allows the plants to acclimate to the brighter, drier outdoor conditions. Plants that are not hardened off before transplanting can experience slow growth and death.
If you have questions on seed starting, please let us know at uge3181@uga.edu or reference the UGA Bulletin #1432: Starting Plants from Seed for the Home Gardener.
