Potting Up Seedlings

tomato transplants
Heritage Farm ~ tomato transplants after potting up

Our tomato plants were started from seed a few weeks ago and placed under the grow lights. Before long, they had outgrown their space and started looking for more nutrients. We tried to keep the space a bit cooler to create a plant with a hardy thick calliper stem. At the two leaf stage the plants were exposed to slight drafts which also helped them to get stronger. Some of the seedlings had grown 4″ to 6″ in height before we had time to ‘pot them up’ which is still OK, because tomatoes are pretty resilient.

If you didn’t use grow lights this season, no worries, but you may notice your seedlings had gotten a bit lanky as they were reaching towards the ambient sunlight when they grew. This potting up process is a good time for you to modify the growth of the plant by using an old gardening trick.

Tomatoes will create new roots along their stems whenever they come in close contact with moisture or soil. This is called ‘Adventitious Roots’ and taking advantage of this natural process is a great way to take a problem and create a healthier solution = a stronger plant.


root types

In some instances, students had tomato seedlings as tall as 8″ with very weak stems. We were able to gently curve the stem around the inside of the new pot a few times leaving only the top 2″ of the plant exposed. By sinking the tomato seedling deep into the individual pot, new roots will form along the stem that is covered with soil. This actually makes a stronger healthier plant in the long run since there are more feeder roots gathering water and nutrients as the plant grows.

Lanky tomato seedlings
This student had tried growing without grow lights which caused weak lanky seedlings. Most of this stem was gently buried beneath the soil in the new pot, allowing new roots to form along the stem of the plant.

In the nursery, our seeds are planted quite dense, so we aim to transplant at the two leaf stage. Home gardeners can wait until the plants are a bit larger. These tomato seedlings were started in individual pellets during a workshop and they are now ready to be potted up into a 4″ pot (or a recycled plastic container).

Heritage Farm Tomato plug

The darker purple stem indicates that all of the work to keep the grow light low, air circulating and cooler growing temperatures had created a strong hardy plant. Even though it has a good start, we would still transplant this deep into the new pot to allow new roots to grow along the stem.

Heritage Farm Tomato pot up
Potted up heirloom tomato seedling is good to grow another few weeks before transplanting.

Keep in mind, some of the weakest lanky seedlings can grow into prolific healthy plants so don’t be discouraged.

Heritage Farm is an educational nursery for Canadian Small Farms & Urban Agriculture. Learn permaculture design, how to build a greenhouse, save seeds, raise chickens, build raised beds, grow organic food, and begin your journey towards a sustainable, healthy, lifestyle. Visit Heritage Farm.ca

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