If you read any advice on growing tomatoes in a wet season, all reports say “Don’t grow in a wet season!”. But you can still grow tomatoes in Canberra in wet condition and get a yield if you apply a few tips and tricks. Including; maintaining good drainage, watering to avoid splashing foliage and increasing air ventilation around your plants.
This advice mostly applies to growing out in the elements in a ‘wetter than average’ temperate Canberra backyard, but you can also maintain these good practices when growing indoors in a greenhouse location too.
Location, location, location!
- Plant in full sun position. Tomatoes love the sun! It helps warm the soil, dry the leaves and reduces humidity.
- Ensure good drainage of your plants. If possible, mound the soil in in-ground beds or grow in raised beds or pots with good draining soil.
- Space your plants openly to maintain good ventilation. Good airflow reduces diseases. Plant at around 60cm to 1m apart.
- Staking is important in both determinate and indeterminate varieties. Provide a sturdy stake or trellace to ensure plants stay upright, separate from other plants and off the ground.
A little extra goes a long way… (optional tip!)
- Add calcium such as lime or finely crushed eggshells to your soil and sulfate of potash. These add crucial micronutrients to the soil for tomatoes and (when combined with consistent watering) help with strong leaf and stem growth, fruit set and to avoid blossom end rot.
Okay I’ve planted my tomatoes, now what?
- Water at the roots, or water with drip irrigation. Avoid wetting the leaves further than the rain already does. Wet leaves can lead to fungal pathogens and other diseases
- Mulch the soil around the plant. Mulch helps avoid the soil splashing back onto your plants leaves as soil can carry pathogens. Just be sure to keep the mulch pulled back from the stem of the plant and not touching the stem or leaves.
- Once the plant has matured, cut off lower stems and leaves. Especially ensure you remove any leaves which touch the ground. Trimming lower leaves also increases ventilation, which reduces the chance of diseases like blight.
- Check the soil dampness and keep track of days since last rain or plant watering. Although it’s a wet season, sometimes Canberra can go weeks without rain. Ensure your tomatoes receive consistent, regular watering, be it through rain or direct watering.
- Maintain regular (weekly) liquid fertiliser as rain will dilute or wash away applications
- Pinch out lateral shoots. Laterals are the little shoots that appear at the join of the branch to stem of the plant. Pinching off laterals will promote better airflow, direct resources into larger fruit and make the plant easier to stake.
- Pinch or cut out any “suckers” from the base (same reason as for the laterals).
- For pruning tips, see this fantastic video by Gardening Australia https://www.abc.net.au/gardening/factsheets/pruning-tomato-plants/11892614
- Tomato flowers are self-pollinating, in that they have both male and female flower parts. Wet seasons create high humidity which makes for “sticky pollen” and so the pollen within the flower doesn’t transfer well and won’t set fruit, or will create ‘wonky’ fruit. You can intervene to help the pollen release from the flower by shaking or flicking the flowers when the temperature is between 20 and 35 degrees. Another option is to use an electric toothbrush and touch that to the flower head to vibrate the pollen out. If the pollen is still viable and the temperatures are within range you should get fruit set.
- Wet seasons can create above average insect activity. While tomato flowers are self-pollinating, insect activity (such as from a visit from a native Blue-banded Bee) can transfer pollen between different plants. This is an issue if you are trying to save seed as a cross pollinated flower will not produce seed which is ‘true to type’. Exclusion bags/grow bags can be used to cover the flower/developing fruit, or insect-grade exclusion netting can be used to cover the whole plant.
Late in the season…
- If your fruit is ripe or almost ripe and rain is in the forecast – pick it! A sudden downpour will flood the cells in the plant and burst the skin of the fruit. You can always ripen any ‘close to ripe’ fruit on your windowsill indoors.
- At the end of the season, upend your whole plant with fruit and all and hang upside down to dry undercover in an area with good ventilation. Fruit will continue to ripen while the leaves dry off. Once dry they are less susceptible to pests (and you make space in your garden for autumn crops!)
Pests and diseases
- Practice good plant hygiene during both wet and dry seasons. Remove any diseased or dead leaves or plants. Do not compost these as the pathogens can linger in the soil.
- Fruit fly are an increasing problem in Canberra and the warm and wet weather combination creates suitable conditions for this pest. If fruit fly occur within 200m of your plant, the best approach is to completely exclude using insect exclusion netting covering your whole plants.
- Wet seasons in temperate areas may create a higher than normal amount of insect activity. Netting also helps control Budworm and other insect pest, plus birds and possums!
What’s your number one tip for a wet season?
Be observant to the weather and your plants. Check on the forecast and on your tomatoes, daily if you can. Look for anything unusual and you can catch issues early on!