Whilst in the past, seed could have been imported for them all, increasing biosecurity regulations and the cost of associated testing, means that in recent years, we’ve had to grow a few of the open pollinated and heirloom varieties ourselves in order to keep them in the range.
If you’re a home gardener and are planning to save a few seeds from your favourite beefsteak passed down to you from your grandfather, the process is relatively easy - remove the seeds from the meat of the fruit, rinse them thoroughly several times, dry them on a paper towel and voilà, you’ll have seeds for next season!
If however, you need to grow sufficient plants to produce seed to fill hundreds if not thousands of packets, to supply numerous farmers’ market growers around the country for several years, the process of growing and harvesting tomatoes for seed reaches a whole new level.
Firstly, very few varieties of tomato produce the same amount of seed and whilst the seed is a similar shape when dried, the seed can vary considerably in size. For example, a cherry tomato will contain quite a few seeds but they’re only a third of the size of a beefsteak seed which often produces just a few quite large seeds.
This year, I grew 1,000 Russian Red tomato plants thinking they would yield 3kg fruit each. I had previously grown other varieties that had produced 1kg seed from 100kg fruit. This would be enough seed (approximately 30kg) to last us and another seed company for the next 5 to 6 years, as tomato seed has a great shelf life. Wrong and wrong again! It was a hot dry summer here in Katikati and many plants just didn’t produce the desired amount of fruit. On top of that, we needed 350kg fruit to yield 1kg clean seed. Unfortunately, we ended up with only 8kg clean seed. Many lessons learnt from this, if I was to grow that many plants in one crop again.
To explain the harvest process better, this is what we did…
The plants were grown well away from any other tomatoes to avoid possibility of cross pollination – in actual fact many books say that an isolation distance of 15 metres between varieties is sufficient.
The fruit is harvested at a fully ripe stage – in the case of Russian Red, it is bright red.
We have a large pulping machine which consists of a filling shoot that drops the fruit between two offset ceramic discs, these squash the fruit and separate the seed from the meat, as it drops to a sloping stainless steel mesh sitting on top of a collection shoot. We’re adding water all the time, with the slurry of seedy water flowing into one bin and the meaty pulp into another bin, the latter is later discarded.
The seed slurry is left to stand overnight during which time, the heavy ripe seed sinks to the bottom of the bin while the much lighter slops rise to the top. The soupy skin filled slop is drained off and the seed at the bottom is rinsed a number of times to remove any remaining residue and plant material. The penultimate rinse includes a mild concentration of hydrochloric acid to clean up any lingering pathogens that could be harbouring on the seed’s surface.
After that the seed is squeezed to remove excess water and spread thinly on sheets of cardboard to dry completely. Once that has occurred, any seed that’s stuck together is rubbed to separate it and then put into airtight foil bags where it will happily store for many years.
A germination test sample is taken every year to ensure the seed maintains its viability.
Nichols on Teviot Street says ...
Thanks for that Gerard it was great to see the process of how you get all that seed.
Dave Jenkins says ...
Hopefully you will have seed available this season of Monte Carlo F1 tomato
In my garden this was a superb beefsteak type plant with great flavor although prone to fungal diseases
Please let me know if available
Barbara from Kings says ...
Unfortunately, Dave, tomato varieties are subject to a great deal of testing as per Gerard's blog. This has meant that some we have had previously, are no longer available to us. Monte Carlo is one of these.
Julie says ...
Yes, Tomato seed has a long life, I returned from working in Aus and had some of your seed 7 years past its sow by date, sowed them anyway and we got a massive crop of big fruit from an oxheart and another variety last summer, kept the seed and another massive crop this year, wonderful stuff!!