Growing San Marzano Tomatoes in Kratky Hydroponics – Update: Week 3

I wouldn’t have believed it a month ago when you said I could grow tomatoes so easily in Kuwait’s hot desert weather; but here I am, just growing tomatoes. Of course I cheated a little by growing them inside the house, in a climate controlled area… and then I removed the soil and decided to grow them hydroponically.

And they are still growing!

My little plant babies are now three weeks old, and wow have they grown. This was them only one week ago:

Their stems had just started to turn brownish tinged close to the cloning collars. They both also had two new branches.

And this is them now, at three weeks old:

I just can’t believe how fast they are growing. I can turn my grow lights off at night, then when I re-enter in the morning they have grown an entire branch! No joking, I have seen an entire baby branch just pop up in the space of a few hours.

I have preemptively placed their first trellis support bars. Since we are using custom painted Ikea Ivar cabinets to hold our plants, we bought the bottle rack as a DIY trellis. This provides some basic support for the plants, and lets me tie them in place. We can also easily raise or lower the bottle rack as needed, and even add more as the tomatoes grow in height.

San Marzano Tomato Week 3, In Kratky Hydroponics
San Marzano Tomato Week 3, In Kratky Hydroponics

This is the weaker of the two tomatoes; he isn’t growing as fast. He now has four branches, two of which are fairly large. I noticed that once the dominate grower had put out one or two smaller branches, he had substantial increase in growth speed. I expect this one would probably grow much faster in the coming week.

The dominate grower is outpacing him pretty fast; he has a total of nine little branches all emerging. He’s also about 2″ (5cm) taller than his sibling. His centre branch is just touching the trellis bars, so hopefully in the next few days he will be resting against it and can be supported with the tie.

San Marzano Tomato Week 3, In Kratky Hydroponics
San Marzano Tomato Week 3, In Kratky Hydroponics

Both tomato plants seem to be developing some good root structures. I couldn’t lift the buckets out too high as the trellis bars are now in the way, but you can see the roots extend much further down into the bucket and nutrient water. The roots are nice and white, which is a sign of plant health when it comes to hydroponics.

San Marzano Tomato Week 3, In Kratky Hydroponics
San Marzano Tomato Week 3, In Kratky Hydroponics

Have you grown tomatoes hydroponically, or maybe traditionally in soil? Do you have any tips to share with a first-time grower?

Seed Germination Temperatures

A bit over a week ago I planted some spinach seeds, and sadly they didn’t germinate. I began a bit of research as to why. Despite my spinach varieties being hardy to warm weather, they still need cooler soil to germinate! The adult growth stage can handle warmer temperatures but the seedlings are too vulnerable still.

I began to wonder what I could grow with my current temperatures. It’ll also be handy to know the minimum temperatures for when the seasons change.

Whilst my plants aren’t being planted in soil, instead hydroponic is usually planted in rock wool or peat moss, the germination temperature should theoretically remain the same.

Optimal °FOptimal °C
Amaranth, Red Leaf68-7520-24
Basil, Purple Petra65–8518-30
Basil, Genovese70 – 9021 – 32
Broccoli45 -85 7-29
Cilantro55-7013-21
Cucumber, Lemon70–9021-32
Kale, Nero Toscana 65–8518-30
Lettuce, Little Gem (Romaine)40-755 – 24
Lettuce, New Red Fire60–7016-21
Lettuce, Red Sails60–7016-21
Lettuce, Red Salad Bowl50-7210-22
Pepper, Cayenne65-9518-35
Pepper, Jalapeño 65-9518-35
Spinach, Matador50–7510-24
Spinach, Lavewa50–7510-24
Spring Onion68-7720-25
Swiss Chard, Bright Lights75–9024-32
Swiss Chard, Lyon50 – 7510 – 24
Taisai, Pak Choy50- 8010 – 27
Tomato, Marmande VR60 – 7015 – 20
Tomato (Cherry), Supersweet 100 FT75 -9021-32
Tomato, Sam Marzano70–9021-32

I measured my Aerogarden water and it’s hitting a maximum of 85°F (30°C)! No wonder my spinach never sprouted, its ideal temperature is 50-75°F (10-24°C). Its just way too hot for them.

I’ll have to wait a while for the weather to get a bit cooler before I can sprout spinach; in the meantime I can try growing some Bright Lights Swiss Chard and Nero Toscana Kale.