Watering Tomatoes – for the novice the first question to ask about growing your tomatoes once you have planted them out into their final growing spot is, how much water and how often? The answer to that depends on where you have planted your seedlings out, i.e., in open garden or in a pot and of course other factors include the season of the year and the temperature.
During the summer when temperatures can be high (we can get 45 degrees (110 + Fahrenheit) you will obviously need to water more frequently because evaporation is going to be high. You can, of course, minimize that with mulch around the stem of the plant. Be careful not to place the mulch right up to the stem as this will encourage fungal diseases to develop.
So, as a rule of thumb if you have planted in an open garden, a good soaking once every two or three days should be sufficient. This will give you regular, even watering and help to avoid blossom end rot.
Remember to mulch to minimize evaporation.
As the temperatures cool off from summer maximums you can scale back your watering to once a week. If you are growing your tomatoes in pots you are most likely using a commercial potting mix which is designed for good drainage so the water gets away quickly. I would suggest in this situation to water daily and if, as in our summer, where we get temperatures of 110 degrees plus to water twice a day.
This will help to overcome a common problem of blossom end rot which occurs if there is a sudden lack of water and calcium to be taken up by the roots. You can recognize this as a black spot at the blossom end of the tomato which can grow to about 1/3 of the size of the tomato and the skin over the spot becomes hard and leathery.
A critical consideration when watering tomatoes is to water at the base of the plant. Don’t water the leaves. Just water the soil at the base of the plant. If you’ve planted in an open garden a soaker hose is a good idea or set up a dripolator system where the water slowly soaks into the soil at the base of the plant.
If you want to be really professional set it up to a timer and you have to spend less time doing the mundane tasks. By watering at the base of the plant the spread of fungal diseases is minimized. This is the greatest bane of tomato growers. Remember, a deep watering to get down to the roots once every two or three days is preferable to a light hosing every day. Deep watering is important!
