Growing tomatoes in Tasmania

Growing Tomatoes in Tasmania?

Growing Tomatoes in Tasmania

There is no one way that is the best way to grow tomatoes. But there are some things that can help you increase your chances of success. When I grew tomatoes in QLD, it was a little different to here in Tasmania due to the heat and humidity differences. Below is how I go about growing each season. I generally produce at least 30 jars of passata (60 in 21/22 season), 5 to 10 jars of kasundi, the same in tomato and chilli jam, tomato sauce for the freezer plus plenty to eat over the January to June months and supply friends.

Late July to late September I start sowing seeds on my hot bed. I have the benefit of a large germinating heat mat in a poly tunnel, however it is handy to purchase a heat mat such as this. They are useful for cucumbers, chillies, capsicums, eggplant and any summer vegetables that needs 21 degrees or more temperature to germinate with vigour. I go by the 8-week rule for germinating. That is about 8 weeks till they can be planted. So starting late July will mean planting late September. In Tasmania this is a bit early to be planting outside but it is good for planting in the hothouse. Mid to late August (even late September) is good for tomato seedlings planted outside. I like to plant at least three batches outside. Some late October and some mid-November and last lot late November to early December. If it is a cool start to the season, I may plant some additional seedlings early to mid December. If you need to pot up the seedlings into a bigger pot then do so if the weather isn’t conducive to planting.

Tomato seedlings at 4 weeks old
Tomato seedlings at 4 weeks old

I plant about 30 to 40 tomato plants outside and many in the hothouses (over 100). I like to save space in the hothouse for the real heat lovers such as cucumber, chilli, capsicum and eggplant. I highly recommend some form of hothouse to expand your growing options in Tassie (see post here). The tomato varieties that are late season and need more heat go in the hothouse and the early to mid-season ones outside. In the hothouse I use grow bags. I like grow bags as I can keep the soil moisture more consistent and I can refresh the growing media each year and compost last years soil. This also minimises disease build up in the hothouse over the seasons. Outside I prepare the bed a few weeks earlier with adding some homemade compost/organic manure (I like sheep or cow). I don’t add anything else at this stage. I also don’t dig my garden beds. You can but I don’t as it impacts on microbial life and the way the soil holds moisture (important for minimising blossom end rot – see this for some good FAQ by an expert – Craig LeHoullier). Also I have found I don’t have anywhere near the weed issues I did when I used to dig over the soil.

Tomato seedlings around 8 weeks old and hardened off.
Tomato seedlings around 8 weeks old and hardened off.

While raising seedlings be careful not to over water them while they are growing. They will become weaker plants. Nice thick hairy stems are ideal. A plant that needs help standing up is a sign of weakness. Likely they have been pampered or lacked sunlight when growing and need hardening off. If you raised the seedlings in a hothouse, it is important to harden them before you plant outside. They should be fine with the natural sunlight if raised in a hothouse but if you raised them in the house, you will need to be careful. Give them a little natural sunlight (say 15 minutes on the first day) then raise it to 30 the next then 45 then and hour then more. But from a hothouse to outside, start with an hour outside then 2 then 3 then 4 but not on a sudden very hot day or very cold day.

Picking the day to plant is the big decision. Many go by the Hobart Show Day (Oct 22 ish) in Southern Tasmania. Generally this is too early. I believe it was meant to be Melbourne Cup Day. The last few years shows with La Nina, the better time to plant without lots and lots of protection has been Nov 20 to early Dec). Cold fronts are common at this time of year and nights below 5 deg Celsius can set the seedlings back a few days. Soil temperatures are important also. If it goes up and down due to cold fronts the seedlings won’t be happy. Tomatoes impacted by cold weather may get a purple discolouration under the leaves. A sign of the soils being too cold for the plant to uptake phosphorous (even though it is there in the soil). The seedling will overcome this most of the time as the weather warms. 20 deg C soil temp is ideal for planting seedlings. 10 deg 1 hour after sunset also.

I like to get some in around late October if there has been reasonable weather that month (sometimes i delay to early Nov) but they go in a raised bed where I have some irrigation pipes bent over the bed and screwed into the sides so I can place agricultural fleece over them to give them warmth and protection. On days in the high teens to low 20’s I take this back and nights below say 7, I put it back over. I add some potash at planting for strong flowers. Maybe some pock mineral for phosphorous back when the compost was added (not every year but every 2 or 3 as our soils lack this).

One tomato bed with hoops and fleece
One tomato bed with hoops and fleece

I don’t fertilise until mid to late November when I see strong growth (Might be early Dec for 2022 poor weather). All I add is some Complete Organic Fertiliser – the recipe offered by Steve Solomon. add water some seasol every 3 weeks. By late November I usually have the bulk of my seedlings planted however the fleece is still there for cold days/nights. I add COF every 3 weeks (well i may miss one sometimes) until late January when you really don’t need anymore fast growth.

Recipe for Complete Organic Fertiliser (COF)

Mix uniformly, in parts by volume:

  • 4 parts seed meal
  • 1/4 part ordinary agricultural lime, best finely ground
  • 1/4 part gypsum (or double the agricultural lime)
  • 1/2 part dolomite lime

Plus, for best results:

  • 1 part bone meal, rock phosphate or high-phosphate guano
  • 1/2 to 1 part kelp meal (or 1 part basalt dust)

You can source ingredients in large bags from places like Roberts (Nutrien now).

Over December to March, keep the soil moisture as consistent as you can.  Drip irrigation is recommend if you don’t have the time. Results will be much better.

The WIND. November and December can be highly erratic in Tasmania, and the fronts that arrive often bring strong winds due to the season changing and the influence of warm air up north and the cold air to the south. Tomatoes hate wind. Wind damage shows by a curling of the leaf. I staple gun some shade cloth along the edge of the garden beds where the winds come from to reduce impact. In the hothouse it isn’t a problem. A pain but the goal is to get to x-mas time I always say. Some seasons it isn’t as bad, but it isn’t often we don’t have a season where one bad front comes in hard. So aim to protect from those forecast winds.

How to support your tomato? I plant both bush and climbing/vining tomatoes. Also called determinate/indeterminate. The bush toms I put four stakes in a square at planting time around the seedling (a distance that fits the plastic tree guard you can buy from places like Mitre 10 as this offers some protection – you can’t fleece everything, well I can’t). As they grow I put string around the stakes. Offers enough support to hold the weight of the tomatoes up. For the climber toms I have a frame of wood over the top of the bed that string hangs down and I attach the growing stems to the string via a clip (You can just bend the string around the stem). The frame is two vertical pieces of wood screwed to the ends of the raised bed and one horizontal piece attached at about 1.8m high (There are many ways to do this in ground – maybe a 2.4m long star pickets banged into the ground and wood screwed between). I am trialling some homemade wire cages this season made out of galvanised mesh. I will pop phots up and see how they go. With this method I won’t thin to a few leaders. I will just trim lower leaves for good air circulation and let them grow wild in the cages. In the hothouse I have string coming down from the ceiling and attach the same way. I like to plant more bush toms in the hothouse to make it easy. Here I use those cages you find at nurseries/shiploads or just 4 stakes and string.

Recently I have also been buying sheets of galvanised mesh and cutting them and bending to make cages. I then just let the indeterminates grow wild in them trimming bottom leaves). 

Tomato - Tigrella with fruit December 8th. You can see the tomato clip and string around the stem.
Tomato – Tigrella with fruit December 8th. You can see the tomato clip and string around the stem.

You can also get some steel mesh and bang two pickets into the bed and grow up the mesh, but personally I like the string as I can reach for tomatoes and trim leaves easier (And good for ventilation if a cool wet humid start to season – bacteria conditions). Spacing – I tend to go closer and I don’t need maximum yields. I want more seed from many varieties. But in the bed for the climbers up string I space about 30 to 40cm. Quite close but I grow two to 4 stems per plant (2 to start and I let another 1 or two go after x-mas) and can ensure soil moisture. The bush toms I plant about 60 to 80cm apart. But more depending on the variety. If you just plant a few, space further apart for maximum yields. I change my spacing each year based on the feeling of the day and experiences of the previous seasons.

As the tomatoes grow, I train them to 2 to 4 main stems up string and pinch out the laterals. As the plants grow, I trim lower leaves below the fruits. Try to not let the leaves touch the ground as this is the common way for bacteria (Septoria) to get up onto leaves and spread. My feeling is yields are no greater this way but tomatoes are bigger as the plant is not overloaded and it is much easier to reduce bacterial issues by keeping good airflow around the plants. For cherry tomato climbers like Tommy Toe / Salad Special, I just let them grow anywhere and everywhere in a separate bed.

In good years I hope to pick the first tomatoes by x-mas day (Dec 16 in the 21/22 season, Calmart and Earlinorth). This depends on the varieties you grow.  Below is a list of earlier ripening tomatoes that have done well for me. They ripen mid Dec thru January depending on the variety and when planted. There are more but these are my picks for a good start.

Trialing for 2022/23 is 42 days, Glacier and Druzba. Results to come.

From here on it is all about managing the growth of the indeterminate (climbers) and keeping water up for consistent soil moisture (This applies to eggplants, Capsicums and Chillies also). By the end of December, the fleece is unlikely to be seen and the plants are tall enough to handle the occasional cooler night, but if by chance a frost occurs, protect them. Some year a freak frost may happen, and frost is very damaging to tomatoes.

Hopefully by January you start getting some fruits. In cool summers the big month seems to be March and warm summers it is February. You can keep picking through April and pick the lot late April and bring inside to ripen in the warmth of the house or hang upside down under cover. I just prefer to put them all in boxes – single layer face down inside as they ripen quicker in the warmer house. Edit: The 21/22 growing season saw a wet November with some extreme cold fronts, one with snow nearly to sea level mid month. This meant cool soils, cool air with humid conditions, prime for fungal issues which saw many tomatoes around the start back off late in the season due to black spot and mildews killing the leaves. Little we can do with these conditions. Tomatoes protected from the cold pulled through and the warmer Dec to March saw my tomatoes ripen quickly. If yours didn’t, they were likely set back heavily by the weather conditions and potentially dry soils (as the rained stopped in Dec). We are due a better Spring!!

Tomato - Cherokee Purple late January 2021.
Tomato – Cherokee Purple late January 2021.

Some notes on flower pollination: I believe the minimum average daily temperatures tomatoes like is 13 degree Celsius. This varies depending on the variety so this is an average. Calmart may be 11 degrees and Brandywine may be 14 or 15. We generally get this from November through to March. Sometimes October is acceptable as well and April also. Sometimes November is ordinary (2021 for example). We don’t know what the weather will be so I go by the average and use fleece where required. If your plants get stunted by experiencing extended cold spells or strong winds, you can expect them to be set back in development. A 3-degree night may set them bay a few days. A run for 3 nights cold maybe even 2 weeks. So, when you get to February and you’re talking about the lack of ripened tomatoes, think back to those cold spells. It is why you’re waiting till mid-March!!

In hotter climates, high temperatures impact flower pollination. When daytime temps remain above 30ºC and nights are 24 ºC and above, pollen can turn sterile and flowers abort. Not as much an issue with cherry tomatoes and not something we have to worry about too much in Tasmania. The flowers are self-fertile so do not need bees and insects to fertilise however sometimes a shake of the plant every day or two may be required. Bumblebees do this by the buzz they create. In a hothouse, a good shake each day is worthwhile. Tomatoes need consistent night temperatures between 10°C and 23°C to set fruit. (A few varieties will set fruit at lower or higher temperatures – lower temps for eg: see above list. Temps of 5°C at night can delay growth by a few days or more if it is a cold spell.

Blossom drop may occur in the spring if daytime temperatures are warm but night temps drop below 13 C (Hence cool climate varieties are great for us as they have a lower temperature tolerance). The tomato plant will suffer damage to immature fruit or loss of flowers. Additionally, when nights become too warm, the pollen grains of the tomato flower begin to burst, thwarting pollination, hence no fruit set (seen in hothouse more than outside). This is doubly true when the air is saturated with relative humidity. For those growing in hothouse, use a thermometer to understand your temps and humidity over the warmer months.

There are many varieties that handle temps better outside these ranges therefore selecting your tomato variety is the key and also growing a number of varieties. In Tassie, selecting cool climate varieties as the bulk of your plantings will boost your success.

When you buy seedlings of tomatoes, look for strong stems with no support. And a flower or two can be beneficial. Don’t snip it off, it is likely your first fruit. Back to the stringing of tomatoes, you don’t have to do this. You can put big stakes in and train a stem up each stake and use string around it. I just use the vertical string as it makes managing many tomatoes simpler and more enjoyable. Plus, space is usually the issue. Oh, and when you buy your tomato seedlings, aim to plant them out the following days or pot them up if you’re not ready. Don’t let them get cold affected outside by cold nights in a small pot. I hope this helps your coming season of tomato growing in some way.

Happy Growing

Dave – Dave’s Seed


tomato protection
Simple form of tomato protection. Mitre 10 and the like sell the plastic coverings. Use stakes or bamboo and your done.
hothouse tomatoes
hothouse tomatoes mid November 2021
hothouse Nov 2022
November 15 2022 hothouse start to the season.

6 thoughts on “Growing Tomatoes in Tasmania?”

  1. Great information, thanks Dave!
    I’m new to gardening (and Tasmania), I have a few plants in the ground that are just starting to produce ripe tomatoes. Looking forward to using your advice next growing season.

  2. another informative article dave, thanks mate, I am currently learning the ins and outs of tomato growing, i live in sub-tropical mackay, queensland. By reading your articles i’m learning that choosing best varieties is key, and accepting that at fruit ripening stage the plants may look heavily affected by disease, no matter how much correct plant management is achieved. You mentioned applying milk mix spray in one of your articles, what is recipie, and what value is this ?
    thanks, cheers, kev

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