Growing tomatoes from seeds or cuttings

Starting tomatoes from seed

Seed PacketIf your growing season is short, like it is here in Alberta, make the most of it by starting your favorite plants indoors. The May long weekend is when I try to have seedlings ready for the garden.

Tomato seeds germinate between 17°C and 20°C that’s about 65° to 70°F and the tomato seed requires darkness to germinate, sow deeply enough to cover completely with planting medium pressed lightly over it to be sure they’re in the dark.

The rule of thumb about planting depth – cover seeds with three times the diameter of the seed itself. Tomato seeds will take about a week from successfully germinating to becoming a seedling, more info on starting plants from seed.

Interested in the science: from seed to seedling?

Tomato SeedlingsTomato plants are dicots, (two cotyledons) meaning the seed is in two parts (think of a peanut) each half being one cotyledon. The cotyledons serve as food storage units for the seedling and they also hold a tiny pair of embryonic leaves.

During that critical week in the life of the tomato, the embryonic plant within the seed will absorb moisture from the growing medium and begin to swell.

The pressure from within the tiny seed will eventually break open the seed coat, the stem and cotyledons will grow upward and roots will push downward. Photosynthesis will begin as soon as the tiny new leaves and stem reach the light. More about photosynthesis

Hardening off and transplanting

Before planting the seedlings outdoors they will need about 10 – 14 days to become acclimated to the outside; this is called the hardening off period. Set the seedlings outdoors and gradually increase their exposure to the drier air, the sunlight and the gentle winds, allowing a bit longer outdoors each day; this process reduces the amount of transplant shock the seedlings will experience.

What is actually happening during the hardening off period is that the seedlings are going into survival mode; they’re getting used to less water and humidity, lower growing temperatures and the breezes of a typical day. The plant is slowing its rate of growth, thickening its leaves with special attention to their protective ‘cuticle’ layer that will prevent moisture in the leaves from escaping too quickly and it’s revving up its production of protein that it will need to consume in the days and months to come (or photosynthesizing).

The seedlings should be brought back inside each night until there’s no longer a threat of frost and nights are staying above 10°C or 50°F.

Will tomatoes grow from cuttings?

Growing tomatoes from seeds or cuttingsTomatoes grow well from stem or leaf bud cuttings. Choose a healthy plant free of discoloration or fungus and with a sharp razor blade cut a section of stem with the leaf attached at the node (the point on the stem where the leaf begins). This will ensure that the cutting includes an axillary bud (the small bud in the angle between the stem and leaf), this is the point from which a new root will form. Place the cutting into a glass of water for several hours; then fill a container with potting soil and poke a hole into the growing medium or potting soil with your finger and place the plant into it.

Plant cuttings and growth hormone

The bottom of the cutting may be dipped in root promoting growth powder to encourage roots. The powder is actually talc into which 1% or less of IBA (indole-3-butyric acid) a naturally occurring plant hormone (auxin) has been added. The auxin will help shift the hormone balance within the plant to favor root formation.

Growing tomatoes from seeds or cuttingsGently press the soil around the base of the cutting covering the area where leaves may have been removed from the stem and keep the plant in a warm place but out of the sunlight for about five days. Gradually acclimate the plant following the hardening off process. Keep the soil moist throughout the process and when it’s ready to be transplanted, water generously to help prevent the plant from experiencing transplanting shock.

The benefit of growing plants from cuttings is the enjoyment of having replicas of favorite plants at no extra cost. For greenhouses it’s an efficient and quick way to replicate the plants that customers want.

Credits: Axillary bud sketch thanks to NGA’s learning garden, pergola awning photo from AA Home Improvement Company Inc. Murray, UT

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