Many gardeners prune off the suckers as the plant grows — these are the vines that sprout from the crotch where a branch meets the main stem. Pruning the suckers is particularly important for indeterminate tomatoes, because it prevents them from growing unreasonably large, and directs more energy to the fruit.
Take care to avoid getting the leaves wet when you water the plant, as this can encourage fungal growth on the leaves.
When the plant flowers, some people find it is helpful to spray it with a dilute solution of epsom salts (1 tablespoon per gallon/4L of water), to provide a boost of magnesium, which helps the plant set fruit. The advisability of using any salt-based fertilizer is debated however.
If the plant’s leaves turn yellow, it may be that additional feeding is needed. You can side dress the plant with compost, or you can spray it with a dilute solution of fish emulsion or seaweed (mixed according to the package directions). If fish or seaweed is used, it should be sprayed on the leaves of the plant. Don’t touch the leaves after spraying, to avoid spreading any fungus to the plant. The plants should be fed no more than twice a month.
It is also helpful to spray the plant with diluted milk at least once during the growing season. Milk has natural anti-fungal and anti-mildew properties. Mix about 1 tablespoon of milk with 1 cup of water (you want about a 1:10 ratio of milk to water). Put the mix in a spray bottle and spray the leaves of the plant, making sure to get the undersides. This may be combined with feeding, and as with feeding, avoid touching the plant when the leaves are wet. This treatment can be repeated up to twice a month if fungus or mildew is a problem. Spoiled milk and powdered milk may be used.
If desired, in late summer you can also prune off branches that do not have flowers or fruit on them (do not do this in early summer, because flowers can emerge at any time). This puts the plant’s energies into the remaining flowers and fruit as the season comes to an end. If your plant still has unripe fruit on it 30-45 days before your first frost date, prune off all remaining flowers, and cut the plant off at about 5 feet from the ground. This will force the plant’s energies into the remaining fruit and give them a better chance of ripening on the vine before the frost.
The fine hairs along the stem of the tomato plant will grow into roots if they touch moist dirt. If you accidentally break a branch off, or even the whole stem, stick it back in the dirt and keep it moist. You may be able to save it! This is also how people can clone their plants to make more from a single planting.
Try to plant in a location that enjoys full sun and remember to water moderately. As a rough idea of the types of climates Tomato does best in, check to see if your local area is within USDA Hardiness Zones 3 and 14. Ensure your soil is loamy and has a ph of between 5.5 and 7.5 as Tomato is a weakly acidic soil - weakly alkaline soil loving plant. Keep in mind when planting that Tomato is thought of as tender, so remember to wait until your soil is warm and the night time temperature is well above freezing before moving outside.
See our list of companion Plants for Tomato to see which plants you should plant in close proximity to encourage growth.