When To Transplant Seedlings From Seed Tray
Gardeners who start their vegetable seedlings indoors not only save money but get to grow crops that are not available locally. However, transplanting the young plants at the right time is critical to the health and productivity of crops so knowing when to transplant seedlings from the seed tray is most important. The seedling’s development and the temperature outside are two important factors to consider.
Seeds are usually started in flats or jiffy pellets and will need to be transplanted twice. After the first set of true leaves appear, plants should be moved to larger containers so they have sufficient room for root development. Leaving them in flats will hinder their growth. The seedlings will remain in these larger containers until it is time to move them to the outdoor garden.
The time to move seedlings outdoors varies from one place to another. Look up your last expected frost date based on your area. This will help you determine the approximate time when it will be safe to transplant your seedlings. Cool-weather crops such as lettuce and broccoli can tolerate lower temperatures and survive mild frosts, while warm-weather crops such as tomatoes and melons grow best when transplanted after the soil has warmed and the chance of frost has passed.
The first leaves to emerge when a seed germinates are called cotyledons. These are not true leaves. Rather, they exist so the plant can produce and store food, through photosynthesis, for its first few weeks of growth. True leaves develop shortly after the cotyledons. Generally, a seedling needs at least one set of true leaves before it is ready for transplant. I wait until their is 4 leaves on a plant. Use the number of true leaves, rather than the size of the plant, to determine when your seedlings are ready to be transplanted.
The shock of moving from a controlled indoor environment to the outdoors can injure or kill tender seedlings. A period of hardening off gently prepares the plants to adapt to their new home. About a week before transplanting to the garden, leave the plants outdoors for brief periods of time. Be sure they are protected from wind and direct sunlight. Each day, increase the amount of time they are outdoors.
When to Transplant your Seedlings
Plants are less likely to experience transplant shock if they are transplanted on a cool, cloudy day. Watering before and after transplanting, since the roots of young seedlings won’t be accustomed to seeking out water. Keep as much of the growing medium as possible around the roots.
Expect the Unexpected
Even with the best planning, the weather can be unpredictable. Protect newly transplanted seedlings overnight if late-season frost is predicted by covering them with thin sheets, overturned coffee cans, or thin clear plastic to trap heat around the plant and keep the cold out. Be sure to remove these protective coverings first thing in the morning.