Q&A - Tomato Growing

Our experts Julie, Tim and Evette answer your questions about growing tomatoes

Plant seedlings when they are 10-15cm tall at 6-8 weeks

Growing and training

Sarah asks “What's the step-by-step guide (detail please) to propagate from seed?”
Raising tomatoes from seed is done using the ‘seedling’ or ‘transplant’ method where the seed is germinated in a small pot or a punnet to be transplanted into the garden later. This method means the plants get a head-start in the pot before planting out and is ideally done in a small greenhouse or in a sunny, protected spot.
Once you’ve got your spot sorted, you’ll need some good quality seed-raising mix and some clean pots or punnets. Fill your container with the mix and firm down gently. Sow you tomato seed on the surface, then lightly sprinkle 1-2mm of mix over the seed. Water these in with a fine shower of water – bottle-top waterers are ideal for this.
Place your sown seed containers in your warm, sunny spot and keep them moist. The seed will germinate in 7-10 days. Cut out at the base any seedlings that are too close to each other so the one you leave can grow on strongly. Once germinated the seedlings will grow on happily in the pot for 3-5 weeks.
When they get to 10-15cm and have roots coming out the base of the pot, they are ready to plant out in the vegie garden – provided soil temperatures are above 15°C.
Ross asks “What is the best type of trellising to use for tomatoes?”
For indeterminate tomatoes (those that keep on growing after flowering) you need tall and strong trellising to support your plants otherwise, once you get to fruiting season, the plants are falling over themselves and disease is invited. We use 2m tall sheets of steel re-enforcing mesh (‘reo’) held in place with star-pickets.
It is best to use two sheets set about 30cm apart with the tomato plants in the middle. This set-up allows you to easily tie in the plants as they grow to create a ‘wall’ of tomato plants that are supported by the mesh.
Belinda asks “What are the best fertilisers for sweet tasting tomatoes and when should they be used?”
The flavour of a tomato is governed more by the varieties and ripeness than by fertilisers. Organic fertilisers such as blood and bone, fish emulsion and well-rotted animal manures are all soil conditioners that are important in providing you tomatoes with a full range of slow-release nutrients, but if you don’t have the right spot (sunny and well-drained) and the best varieties, no amount of fertiliser will sweeten your tomatoes.
Kim asks “When do you sow tomato seeds and how do you get seedlings going so that you have good-sized seedlings ready to be planted out in early November?”
Follow the answer to Sarah's question for how to get your seedlings going. As for when to start for a November plant-out, work back from the planting date allowing 4-6 weeks after germination for the plants to fill the pots. So by sowing in late August you should be getting into gear.
Luda asks “What is the distance you should plant them in the garden?”
For the indeterminate varieties, the ideal spacing is about 1 metre apart so that you can get good air movement around the leaves and fruit. If you plant closer than this you will need to prune quite a lot to avoid an over-crowded canopy and this will reduce your crop.
Don’t fall into the trap of thinking that the more plants I plant, the more fruit I’ll get – this only works if you give each plant enough room to grow.
Craig asks “How often should you water them?”
A perennial question and one that is hard to give a simple answer to (which is probably why it keeps on coming up!). The two biggest factors at play here are your soil and the weather. If you have a few days of hot winds and you have sandy soils that don’t hold moisture very well, then you will need to water a couple of times a day.
If you are have heavy clayey soil and it’s been raining a bit, you probably won’t need to water at all. The key is observation and preparation so you can get it just right.
If you know there’s a hot spell coming in the next few days, get onto it early so you can deep water the roots in the days leading up to this. It is far better to go into a hot spell with water already around the roots, than to apply water on the hot days after your plants are already parched and wilting.
Alexander asks “When should you plant tomatoes in Melbourne?”
Being frost tender annuals you can start sowing indoors on a heat mat in August. Tomatoes need a soil temperature of 15-30°C to germinate. Plant them out in the garden from September once the soil temperature is at least 15°C.
Ami asks “Will they grow in a poly tunnel without direct sunlight? And if so, when can I plant seeds? Located in the Western District, near Forrest.”
Tomatoes need at least six hours of direct sunlight per day to grow and crop. Sorry to break it to you Ami, but even a poly tunnel will not help if you don’t have direct sunlight. A poly tunnel is useful in climates where you get late spring cold weather snaps as they afford some protection from the cold nights, and they can also extend the season for ripening in the autumn. But tomatoes need sunlight to thrive.
Peter asks “Is it OK to pinch out the terminal bud once they have reached manageable height, i.e. to keep the height manageable? Does it effect yield?”
Will Trueman, our Seymour Heritage Farm Manager conducted a trial on tomato pruning in the late 1990s and the results were emphatic! He compared the yields of Tigerella and Gross Lisse pruned and unpruned and found a 25% (for lightly pruned) and 83% (for heavily pruned) reduction respectively in these varieties. The reduction in yield occurs because, by pruning out laterals, flowering is delayed.
If you live in a short summer season (150-180 growing days) this delay is irrecoverable. If you live in an area with a longer season (250 days plus), the flowering delay may recover and you will maintain yield.
Pruning is only really relevant for the indeterminate varieties, that continue to grow after flowering (most heirlooms fall into this category). Pinching out the terminal bud (that’s the top growing point) at about 5-6 foot will encourage laterals (side branches) to grow. This will help set earlier fruit, but it will reduce yield.

Brown patches can indicate Blossom End Rot

Pests and diseases

Carly asks “What is the best control for fruit fly? Preferably organic.”
Diggers stocks a pesticide-free lure for attracting and killing the QLD male fruit fly. This product is a BFA registered allowable input (Organic) that attracts the male fruit fly therefore breaking the fruit fly cycle (search code HFFA at diggers.com.au).
We also stock a Mediterranean fruit fly trap. This all-natural organic attractant is irresistible to male Mediterranean fruit flies and will not harm any beneficial insects. Simply hang the trap in or around your fruit trees to trap and kill the male fruit fly.
This allows you to reduce the number of fruit flies and, when used all year round, it detects the onset of the fruit fly season. One trap covers an average household block. With a heavy infestation three units may be needed over a three year cycle.
Dispose of infected fruit into bags and into rubbish collection (search code HMFFT at diggers.com.au).
“My lovely, ripe tomatoes are have dark brown patches on the bottom and look like they are rotting. What have I done wrong? ”
It sounds like they were affected by ‘blossom end rot’ which is caused by calcium deficiency, often due to dry conditions at the plant roots inhibiting its uptake. Lack of calcium causes cells to collapse and discolour. A very acidic growing medium increases the problem, so adding lime or gypsum can help to alleviate the problem.
To prevent the problem, ensure an adequate and regular water supply. If rot does develop, remove affected fruits and improve irrigation.

Determinate tomato varieties are perfect for pots

Varieties

Courtney asks about the “Best tomatoes to grow in a pot/tub? And a how-to for a gardener whom is yet to develop a green thumb!”
The best varieties to grow in a tub are the determinate or short bush varieties. We would recommend Green Grape, Principe Borghese, Legend or Tiny Tommy for a very small pot. You should still provide some kind of stake or support for the plants but it doesn’t need to be too tall- around one metre high should be enough.
You will definitely need to grow in a really good quality potting mix in a pot with that is at least 30cm x 60cm. Start the seeds off in a punnet then transplant to a small pot to grow on for 6-8 weeks and then transplant the tomato into its final growing position in the large pot.
You will need to liquid fertilise the plant throughout the growing season with a top quality organic fertiliser. Water as necessary. The pot will need to be kept in a sunny position that has good air circulation around it.
James asks “Are their ancient relatives from which they were cultivated from still exist or were they bred out?”
The wild ancestors of the tomato do still exist but are a different species the tomatoes we eat today. Wild tomatoes, (Solanum pimpinellifolium as opposed to Lycopersicon esculentum), are much hardier and have smaller fruit than the juicy plump tomatoes we prefer to grow. Wild tomato species can still be found in South America, particularly the Galapagos, but I am not aware of anywhere you can buy seeds. We do have a wonderful currant size tomato called Wild Sweetie that seems to still carry many of the traits of its wild relatives!
Beverley asks how “... to tell determinate from indeterminate and a mnemonic for which one to prune ... I always forget!”
A determinate tomato is one that reaches a certain height and flowering stops, so that is why they are often called bush tomatoes. They also tend to produce all of the fruit at the one time and then their season is over. Indeterminates are also known as vine tomatoes and they keep flowering and producing until the cold stops them in their tracks. They are invariably the best tasting cultivars — Green Grape is exceptional.
If you do chose to prune your tomatoes then you only do this to the indeterminate or vining types but, as discussed earlier, you will reduce your yield.
As for a mnemonic to help you remember I can't come up with anything more exciting than the bush (or determinate) varieties are more determined to produce their fruit all at once. Hope this helps!
Edward asks “What is the best variety for Hobart?”
Any of the varieties with short harvest season would be good for Hobart. Some of our early fruiting varieties are Lemon Drop, Jaune Flamme, Principe Borghese, Valentine, Beams Yellow Pear, Purple Russian, Black Cherry, Periforme and Grosse Lisse. If you are after a good one for a pot then we were still picking Green Grape tomatoes from a potted plant in June!

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