As promised last time, this time I report on the tomato half of the passive hydroponic experiment. Executive summary:
⇒ Passive hydroponics worked.
⇒ Potting mix worked better.
This grow isn't over yet (growlog here), and it's had significant problems. But the experiment is 15 weeks along, and I've harvested 67 tomatoes.
For this experiment, I grew two dwarf cherry tomato varieties, sweet n neat and red robin. Both varieties are determinate and grow only 8-12" tall. Space was tight, so I grew one of each variety in two small self-watering pots, maybe 2 liters capacity. Definitely crowded.
The passive hydroponic pot got coirstone substrate and hydroponic nutrients as usual for tomatoes. (Covered in my book – tomato nutes are complicated.) The "coirstone" substrate was half growstones and half coco coir. The other pot got Miracle Gro potting mix, with a bit of lime and organic tomato fertilizer (Gurney's Tomatoes Alive!). Both pots got the same artifical light – CFLs – in the same enclosure.
They both got diseased – my best guess is bread yeast. But tomatoes always get diseased. If the coirstone treatment were more diseased, it would be hard to draw a conclusion. But the potting mix plants were more damaged.
The coirstone tomato plants have bigger fruit. But I've harvested twice as many from the devastated potting mix plants. More importantly, the potting mix tomatoes taste better. A lot better. The potting mix fruit taste like ripe supermarket cherry tomatoes. The passive hydroponic tomatoes have the texture of a cherry combined with the vapid-sour flavor of the worst supermarket tomatoes. Blech.
I'm growing another hydroponic cherry tomato at the same time, in a CropLampSurround lightscreen in a tall Aerogarden (growlog here). The coirstone and lightscreen grows were fed the same nutrients. The lightscreen tomatoes are excellent, the best cherry tomatoes I've ever eaten.
With better light, more room, and healthy leaves, the potting mix dwarf cherry tomatoes would be better, but not that good. The larger, indeterminate lightscreen tomato is a much better tasting variety.
The passive hydroponic tomatoes would taste better under better conditions. But they would still taste the worst of the three treatments.
Why? I can grow good-tasting dwarf cherry tomatoes in potting mix. I can grow great-tasting indeterminate cherry tomatoes in deep water hydroponics. But the coirstone tomatoes – with the same nutes – blech. My guess is that to improve the coirstone results, the next step would be to rinse out the coirstone, and work hard at pH balancing the nutes. Also, tomatoes aren't as water-tolerant as lettuce. Increasing the stone-to-coir ratio might help.
But it's easier to use potting mix. And very bright lights.
Any interest in a passive hydroponic greens growing product? The coirstone system worked well for growing lettuce.
What's Growing Now?
Still harvesting lettuce, stir-fry brassicas, cucumbers, and lots of tomatoes. My seedling shelf is completely full now, with baby flowers and vegetables getting ready for spring. It's looking like a cold late spring and cool summer, so I'm hedging my outdoor plans toward cooler crops – more greens, no melons, advanced tomatoes and very advanced peppers.
What are you growing now?