Urban Food Garden

Stressing Tomato Plants To Encourage Early Fruiting

Here in the Rat (Ballarat) the food gardening Holy Grail is to get ripe tomatoes by Christmas.  Yet food gardeners often tell me that they struggle to get ripe fruit by February, let alone Christmas.  This page gives you some hints on how to produce early season tomatoes.

Why tomato plants can take a long time to set their first ripe fruit

 There are two main reasons why tomato plants can be slow to set fruit.

    To set fruit early you need to grow tomato varieties that are early cropping and suited to your local climate.  For example, here in Ballarat (which is in the Cool Mountainous climate zone) Rouge de Marmande (early cropping variety that likes cooler conditions) will produce ripe fruit a good three to four weeks earlier than Grosse Lisse.  Seek out early fruiting tomato varieties and consult with experienced local food gardeners as to what varieties of tomatoes do best in your area.
    Though note that early fruiting tomatoes may not be the most productive or best tasting.  It is best to grow a variety of tomatoes in a given season.

    If conditions are good (well manured soil and plenty of water) tomato plants will put most of their energy into growing laterals at the start of the season, and very little into producing fruit.  It is not until late summer/early autumn that they switch to putting most of their energy into fruit.  However, if conditions are not good, they will put more of their energy into producing fruit in the early stages.

    The trick to getting early tomatoes is to stress the plants a little to encourage fruit production, but not enough to reduce overall yields by stunting growth.

stressing tomato plants in the ground
    Tomatoes planted into soil with low nutrient levels are more likely to set early fruit than ones planted into heavily manured beds.  Add more manure once some fruit have set to encourage large fruit and vigorous growth.
    The easiest way to stress tomato plants is to let the bed they are in dry out to the point where their leaves droop a bit.  Plants that are stressed because of lack of water will set fruit much earlier than ones that are not stressed.
    While I have never done this myself, one method used by traditional vegetable gardeners to encourage early tomatoes is to dig up one or two plants and then replant them straight away in the same spot.  I am told that the stress this puts on the plant’s roots encourages them to set fruit much earlier than plants that were not dug up.
Stressing plants in pots

The problem with stressing tomato plants in the ground is that if it is a wet spring it is hard to let the bed they are in dry out.  And I have always been uncomfortable about planting tomatoes into a poorly manured bed.  While I have stressed tomato plants in the ground in the past these days I prefer to stress them while in pots prior to planting out.  And then only by stressing them with lack of water, not lack of fertiliser. 

To do this, when seedlings I am growing are ready to be planted out I plant them into pots instead of in the ground, then at some stage in their time in the pot I stress them by letting the pots dry out a little.  By stressing them in this manner they will usually have set some flowers by the time they are planted out.  Those flowers will then go on to produce early fruit.

LEFT: Tomato plant in a 14cm pot with some flowers on it.  RIGHT: Closeup of the flowers.  When the plant is finally planted in the garden it will already be well on the way to producing early fruit.

negative side effects of stressing tomato plants

Stressing tomato plants weakens them, and weak plants are more susceptible to pests and disease.  So, it is important to only stress some of your plants and not to stress them too much.  But tomato plants are tough, and as long as you do not overstress them, they will go onto produce a normal healthy crop, as well as an early one!