Lenore Linton, Master Gardener
I have been growing tomatoes for 56 years, but it is only in the last 20 years that I’ve been starting them from seed. For 36 years I bought my starter plants at a local greenhouse. I had my favorites: Big Beef, Better Boy, First Lady, Early Girl and Sweet 100, before that Manitoba. I always had plenty of tomatoes for fresh eating as well as sharing, sauce making and freezing.
When I retired in 1996 I began gardening with a passion. My adventures growing tomatoes started with a package of heirloom seeds. If I remember correctly it was Anna Russian or Early Annie. I was hooked. If I was to grow heirloom tomatoes I needed to grow them from seed as they were not available as starter plants.
One of the first rules I quickly learned was not to be in a rush to plant tomato seeds. The next lesson was the importance of adequate light for the young seedlings. I keep these two lessons in mind as I start my tomatoes. Otherwise you end up with tall spindly plants before planting time.
I never plant my tomato seeds before April 1. The directions on most seed packs and many seed catalogues are to plant 5 to 7 weeks before the last frost date, which in Winnipeg is between May 21 and 31. When looking over my records I see that I’ve planted my tomatoes in the garden as early as May 15 and as late as May 25, much depending on spring weather and the temperature of the soil. The earliest I have planted tomato seeds is April 1 and the latest April 8. In 2017 I planted seeds on April 1 and planted out in the garden May 24. In 2018 I planted seeds on April 1 and planted out in the garden May 15.
How much space do I have to grow tomatoes, remembering that they need at least 6 hours of sunlight each day? Remember this when planting and ordering seeds.
When I receive my seeds I mark the date on the package with a permanent marker. Tomato seeds are viable for 5 years or more if stored in a cool dry place. I store mine in a cookie tin with a tightly fitting lid in my basement cold room.
I use a seed starting mix (not a potting mix) which I dampen thoroughly several hours before filling the planting containers. I use warm water to which I add about ½ tsp of kelp powder to 4 liters of water.
As I reuse containers it is important that the containers are very clean and rinsed in a bleach solution.
As I grow 5 or 6 different varieties I use a different container for each variety. I choose containers that are 2 ½ inches deep with 3 or 4 drainage holes and 2 1/2 inches square. Before filling each container, each is labeled with black permanent marker on a piece of masking tape. I place the containers in plastic greens boxes which I use as mini greenhouses for germinating the seeds. The labels attached to the containers will allow the lids of the plastic greens boxes to close.
Tomatoes do not need light to germinate but an optimal soil temperature of 25-35C ensures quick germination. In each container I plant 4 or 5 seeds ¼ inch deep. I place 6 containers in a plastic spinach box with the lid closed. The boxes are placed on heating mats, which I’ve set up on a card table in my dining room. Many seeds will have sprouted in 4 days, most by 6 days.
As soon as the first green sprouts appear in a container it is removed from the mini greenhouse and set under grow lights in our basement where it is much cooler. I don’t wait for each seed to show green; if you do you will find that the first ones to germinate will have grown weak and spindly in the inadequate light. The little slow pokes will eventually catch up. The grow lights should be about 4 inches above the seedlings and on a timer so seedlings receive fourteen to sixteen hours of light each day. It is important not to over water seedlings. Only water when the surface of the planting mix becomes dry. I use warm water in which is dissolved a ½ teaspoon of powdered kelp. I set each container in a tray of this solution; allowing the water to be absorbed through the drainage holes.
In ten to fourteen days most seedlings will have the first pair of true leaves and are now ready to be transplanted into individual 3½ inch square by 3½ inch deep labeled plastic pots. I use the same seed starting mix as I used for planting with the addition of worm castings (unless the seed starting mix already contained worm castings). The mixture is about ¼ worm castings and ¾ seed starting mix. At this stage the roots of the seedlings are easily separated. I usually empty a container of seedlings out on an old cookie sheet, using my fingers and a popsicle stick to separate them being careful not to break the stem. Roots will form on the stems of tomatoes if covered with soil so I plant the seedlings deeply to the depth of the first leaf. This encourages a strong root system on stockier plants. It is often warm enough by this time for the seedlings to be in the green house, however the young transplants need to be out of direct sunlight for a couple of days until they get over the shock of being transplanted.
It is important to watch the temperature in my little greenhouse closely. On sunny days the temperature can quickly soar to over 30C. In this case I open the door and windows and sometimes even use a small fan. In spite of these efforts afternoon temperatures often surpass the ideal 16 – 21C. However, a heater is still needed at night to ensure the temperature does not fall too low.
It is important that seedlings be hardened off to the outside environment of sun and wind. I do this by moving my seedlings from the green house to the cold frame gradually increasing the time each day depending on the weather. The first day I put them out in the morning when the cold frame is still in shade and the lid partly open. Like transplanting into the garden this process is best done on a cloudy calm day. When plants are growing in the cold frame it is important to open the lid early in the day as plants can fry quickly with hot sun shining into the closed space. Soon the lids on the cold frame can be left open day and night unless there are strong winds, heavy rain or frost warnings.
I keep plants in containers at least as deep as the plant is tall especially during the first 6 weeks of growth. I have found that because temperatures in my greenhouse often exceed the ideal 16 – 21C many of my seedlings grow taller than their containers. In this situation I repot them into larger deeper pots that allow roots room to grow and support the plant growth above. I use pots 4 inches wide and at least 5 inches deep. Again the plants are planted deeply with soil covering the stem up to the first leaves, allowing more roots to develop. When planted in the garden these plants are larger and with thicker stems than those I don’t repot.
I know some gardeners are successful planting seeds in 8 ounce plastic cups where they grow until planted out in the garden. This spring I shall plant the fourteen-day-old seedlings into different sized pots to compare. My goal is to have strong healthy plants with good root systems but not root bound when planting.
In the May newsletter I will discuss growing tomatoes from transplants to harvest.
For further reading Lenore recommends:
The Book of Garden Secrets by Dorothy Hinshaw Patent and Diane E. Bilderback. The authors garden in western Montana.
Tomato Favorites by Lois Hole who gardened in St Albert, Alberta.
The two above books are out of print but still in the Winnipeg Public Library system.
Last year I discovered Epic Tomatoes by Craig LeHoullier. Craig gardens in Raleigh North Carolina (USDA Zone 7b). Different conditions than the just over 100 frost free summer days of Manitoba, Montana or Alberta. He has extensive experience growing tomatoes, especially heirlooms, and the book will answer many questions on growing tomatoes. This book is available in bookstores as well as the library system.