Skip to Main Content / Passer au contenu

Resource Library

Above Image: A row of tomato seedlings sprouting in a garden © YuriyS,

If you and your students wish to extend the Tomatosphere™ program to include additional plant-based inquiries or if you plan to grow the tomato plants until they produce fruit, follow these transplanting and growing recommendations.

Growing Plants Indoors


After several weeks of growth, plan to transfer the plants, including the peat pellets, to the final indoor containers. Ideally these should be 10 to 20 litre pots with good drainage. For soil, it is best to use a good quality potting soil; look for brand that contains peat moss and perlite. Leave the plants in the pellets to avoid disturbing the roots and soak the pellets before transplanting. Bury the plant halfway up the stem and do not be concerned if bottom leaves become covered with soil. When transplanting always handle the delicate seedlings with care.

Moving Plants Outdoors

Tomato plants must undergo an acclimatization process called hardening (or cold hardening) before they can survive outdoors. After approximately six weeks of indoor growth, set the plants in pots or trays outdoors for a short period of time each day to acclimatize them to the cold, sunlight and wind. The first exposure should last approximately 15 minutes. Gradually lengthen the exposure time to several hours per day during a two-week period. Do not set the plants in direct sunlight or in a windy location during hardening. Water the plants sparingly and do not apply fertilizer. After two weeks of hardening, the plants may be transplanted into soil outdoors as long as the daytime temperature generally exceeds 15°C and there is no danger of minimum temperatures below 5°C at night. Always wait until there is no chance of frost to plant outdoors.

Pick a cloudy day to move plants outdoors so the plants will not become water-stressed. Soak the root ball in water immediately before transplanting. Place the stem of the plant halfway down in the soil. New roots will form where the stem is buried and anchor the plant in the soil. Water the newly transferred plant until the soil is quite moist, but avoid leaving it in standing water. Continue to water daily but do not completely saturate the soil.

Flowering and Pollination

Tomato flowers will begin to appear about 30 days after transplanting and will be ready for self-pollination. Indoors or outdoors, it is beneficial to assist this self-pollination process by lightly shaking the plants several times per week while the flowers are open, holding the plant in the middle of the main stem with the thumb and forefinger . Tomato plants grown outdoors will also get help with pollination from wind and the activity of pollinating insects such as bumble bees.

Supporting Growing Tomato Plants

After the plants have achieved a height of 35 cm, they will need extra support. Staking up developing tomatoes also keeps them away from slugs on the ground. Using strips of soft cloth (about 2 cm by 25 cm), tie the plant stem in 2-3 places to a support stake that extends at least 1 metre above the ground.

Wire tomato cages or other commercial support devices (poles, sticks, posts, garden clips, string, plastic cable ties, stretch ties, flagging tape, etc.) may also be used. To avoid damaging the plant, it is best to place the cage or other support devices around the plant while it is still relatively small and allow the plant to grow into the support .

Lighting Needs for Growing Tomatoes

Tomatoes needs at least 8 hours a day of sunlight to produce fruit, but aim to provide 12 -16 hours of light for the best growing results. Tomato plants are day-neutral, meaning that they will flower independently of the day length. Plants grown indoors should be placed near a south-facing window in a location that is free of drafts.

If your room lacks good windows and sun exposure or the winter daylight hours in your location are very short, you can provide additional lighting. There are a wide variety of affordable commercial grow lights available that will support tomato plant light requirements. For more information about using grow lights for growing tomatoes see the Additional Resources section below. If your school has a greenhouse or there is a local greenhouse, make arrangements to grow your tomato plants there, where they will be sure to receive adequate amounts of natural light.

Additional Resources

Government of Nova Scotia. Nova Scotia School Garden Resource Guide. (Accessed February 17, 2016)

This guide focuses on how to start a school garden and on curriculum links so teachers can integrate the garden into their lessons. The guide also includes information on resources available to schools in Nova Scotia and links to gardening information and contacts.

OMAFRA. The Online Gardener's Handbook 2010 Chapter 4: Vegetables Growing Tips (Accessed February 18, 2016)

This webpage from Ontario Ministry of Agriculture, Food and Rural Affairs offers general tips for growing vegetables, including tomatoes.

OMAFRA. The Online Gardener's Handbook 2010 Chapter 4: Vegetables Tomato. (Accessed February 18, 2016)

This webpage provides descriptions of various tomato pests along with suggested management options that do not require the use of pesticides.

SPEC’S School Garden Start-up Guide. (Accessed February 17, 2016)

This guide provides useful information on how to set up a school garden and offers specific information regarding related resources available to teachers in British Columbia.

Tomato Dirt. Tomato Grow Lights Explained. (Accessed February 18, 2016)

This webpage describes the different types of grow lights that are available and the light spectrum needs of tomatoes.