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View Full Version : My primitive hydroponic lettuce - yum!



Gina
8-31-11, 3:01am
http://www.simplelivingforum.net/attachment.php?attachmentid=524&d=1314768760

After reading about growing lettuce hydroponically outside in the sun in hot central Australia over their hot summers, I decided to try to grow lettuce through the summer this year. They use fancier set-ups, but I have been successful with what is called 'passive' hydroponics. This is the simplist, most primitive form and requires no special apparatus, just standing water - or rather dilute mineral solution. I use miracle grow and ammonium sulfate with epsom salts and a calcium source added. This is diluted 1 tsp/gallon, plus a little vinegar added to the water to reduce our high pH. I apply this once/week or so, and also add tap water to the basins so nothing ever goes dry. If there is too much fertilizer, the tips of the leaves will burn. I keep about a half inch of liquid in the 'trays' at all times.

We have had mild weather this summer along the coast, with only a few days of over 80*s. If the leaves are wilting on a hot day or windy day, I will cover the set-up with shade cloth for a few hours, though I prefer not to since that's added work. I've only had to do that twice this summer. I'll also mist the leaves if I am walking past on a warm day.

The medium is half perlite, half planting mix. I am using black plastic plant bands that are used for rooting cuttings. They are 2.5X2.5 X5inches tall. I think regular 4 inch plastic pots would work too. these are standing in anything that holds water. Most of the containers with the more mature lettuce plants are regular nursery flats ca. 15 X 15 inches, with unpunctured plastic in the bottom as the solution reservoir. There are newspapers beneath to help prevent punctures.

The lettuce is purchased seed, then germinated in plug flats. I use many varieties but in summer prefer the crisp head batavians. Any lettuce that is labeled 'slow to bolt', or 'heat resistent' would be a good candidate to try.

Because of our voracious critters (birds, ground squirrels, rabbits, gophers) the lettuce is enclosed on all sides by wire. There is also wire over the top that is rolled back for the photo (and of course harvest.) And everything is on a raised 'table'.

This evening I harvested the first leaves of these plants after taking the picture. It was so tender and luscious, it was almost a crime to eat it. :~) I'm definitely doing this again next summer. And soon I'll also be trying to grow some oriental greens using the same system.

Gardenarian
8-31-11, 6:53pm
This is awesome! I'm thinking I could do this on our deck = no slugs! Question about the planting mix - perlite is pretty expensive; is there anything else that can be used to "lighten" the soil?
Thanks! Very cool!

Gina
9-1-11, 1:57pm
Thanks, it is easier than it might look. It's great not having water the lettuce all the time. And my set-up is also on the back deck/patio hence saving garden space. I doubt I will ever grow lettuce in the ground again.

You are right - no slugs or snails. And for that matter, very little dirt on harvested leaves. Like lettuce in the ground, they do get afew aphids when they get older, but those are very easily washed off.

Alternatives to perlite I don't really know. I've read of people using straight sand, but that is heavier to deal with. The perlite I use is from an ag supply company. I purchased a really large bag (2 cubic feet) a couple years ago for about $15. I use it for mixing other planting mixes too. Fortunately I have the space to store such things.

edit: I looked at my large perlite bag today and it was 6 cubic feet for about $15 - not 2 ft.

puglogic
9-2-11, 5:23pm
Gina, what are you using for your "basins" or "reservoirs" around the black plastic pots? Are those.....roasting pans I see??? So the recipe, as I'm reading it is:

Bottom: newspaper
Then: Reservoir of some sort
Then: Black plastic pots filled with 1/2 perlite and 1/2 planting mix
Then: Plant seeds!
Keeping the reservoirs about 1/2" filled with your fertilizer solution.

Do I have that right? I'd love to try this next year, or even this winter under lights.

Gina
9-5-11, 3:22pm
The pans you see are those larger ones used to serve food from in buffets, etc. And the white one is a large photo processing tray. Yard sale finds. :)

I use anything that is low and holds water. If you have containers that do not leak, you don't need anything else. Even a leveled cookie sheet with higher sides would work - though if made of aluminum, over time those can pit. Plastic trays can work too, but over time, if they don't have uv inhibitors, the sun can ruin them.

If you do not have enough flattish containers that don't hold water, you have to do more. The 'other' containers I use are those black plastic nursery flats with the mesh bottoms - so I have to line them with plastic sheeting that won't leak. That is where the newspaper comes in - it works as a cushion between the rough bottom of the nursery flat and the sheet of plastic. And over that I put another sheet of plastic for futher protection. So the layering goes - nursery flat, newspaper cushion, non-leaking plastic sheet, another piece of protective plastic on top of the non-leaking plastic, and on top of this goes the pots with lettuce. This type of set-up is what the more mature lettuce plants in the photo are sitting in.

The plastic pots are filled with half perlite, half planting mix.

I plant my seeds in plug flats and trans plant into my pots - more space efficient, though you could plant several seeds in each pot, and eat any extras as baby greens. http://www.simplelivingforum.net/attachment.php?attachmentid=141&d=1294381296

As to the level of liquid, that can be variable. A half inch is a good level to strive for. But I don't use fertlizer solution all the time - I don't want to burn the leaf tips. I just add that dilute soluton to the pots a time or two a week. I could probably do it more often, but I'm being cautious. When keeping the trays partially filled with liquid, I just use the hose.

Yesterday I planted some Frisee (frilly endive) and oriental greens. I've read that the frisee is supposed to do really well with hydroponics. Today I'm hoping to transplant some spinach seedlings.

When the weather really cools again, I'll most likely go back to growing it in the soil (in a wire enclosed 'salad table'). The hydroponics is just something to be able to grow lettuce when it's hot and dry in summer and not worry about watering all the time. But we'll see what works better even then. This certainly is easy and has benefits.