Using Grow Lights for Salad in Winter

, written by Jeremy Dore gb flag

Grow light salad leaves

An interesting innovation to appear in UK supermarkets in recent years has been Living Salads – baby leaf salad distributed in the same way as fresh potted herbs. Retailing at around £2 ($3) for a small tray, the leaves continue growing right until the moment they are cut for the plate which is much better than chlorine-washed salad bags that wilt quickly. Having seen these arrive at our local supermarket, it set me thinking about whether I could produce something similar. I love the challenge of trying something new, so this winter I set out to grow my own ‘living salad’ at home...

Growing Salad Indoors

Commercially produced living salads in the UK are grown in large greenhouses which produce over 7,000 trays per week. My resources are more limited and I wanted to find a way to grow the salad without having to heat my greenhouse as that would make it prohibitively expensive to grow, as well as wasting energy.

Last year I purchased a grow light after reading Barbara’s article on Growing Seedlings Without a Greenhouse. As I don’t need to use the grow light to start raising seedlings until the end of February, using it to grow salad was the perfect match. Placing the grow light in an upstairs bedroom gives the advantage of keeping it consistently warm (heat rises in the house) and supplementing the light is much cheaper than heating a greenhouse. In large greenhouses the atmosphere is often supplemented with carbon dioxide which plants take in through photosynthesis. I have no proof that it makes any difference but I also wondered whether all the CO2 breathed out at night in the bedroom would help?

Salad seedlings under the grow light
Salad seedlings under the grow light

Setting up the Grow Light System

Not all salad leaf types are suitable for growing as baby-leaf salads. I chose varieties that work well for cut-and-come-again harvesting where you can remove a few leaves every week, extending production over a longer period:

  • Oak-leaf lettuce: this always grows reliably
  • Loose-leaf lettuce: a few varieties that I had left over from previous years and that I knew produced reliable leaves that don’t brown at the edges
  • Spinach: a strong variety with resistance to bolting that I had a lot of success with last summer
  • Arugula: always good to add a delicious flavor to salad mixes, I use the salad arugula types rather than wild arugula which tends to produce hotter, smaller leaves

The grow light kit that I have comes with four trays and the option of a self-watering base which is a reservoir with capillary matting to wick the moisture up to the trays. I filled each tray with sterile potting soil suitable for seeds and spread about a teaspoon of seeds over each tray covering them with a thin topping of soil. Finally, I gave them a good watering with a fine-rosed watering can.

Once the seeds had germinated the light needed to be kept on during the day and switched off at night. Generally a grow light should be on for about 14-16 hours and off for at least 8 hours of darkness to ensure that the plants keep their natural rhythm of growth.

Thinning and Harvesting the Salad

Within the confined space of the growing trays the salad plants have much less room than normal so it’s vital to keep them very well watered and use high-quality compost to supply ample nutrients. At first I watered only from above but soon found that using the self-watering base with capillary matting gave much faster growth.

Equally important is thinning out the plants. About three weeks after germination I cut out any plants that were closer than an inch apart and this made a welcome microgreen salad just before Christmas. It is important to do this thinning by snipping off the plants just above soil level rather than pulling them up, which would disturb the roots of the neighboring seedlings.

Salad after 6 weeks
Salad after 6 weeks

As the leaves grew the light assembly needed to be raised so that the plants didn’t get scorched. As a general guide I found the lights should be kept 10cm (4 inches) above the highest leaf.

By week 6 the leaves were looking strong and ready for the first harvest. In order to keep the plants growing stronger I again thinned out the plants as well as removing a few strong leaves, leaving about half the leaves to continue growing. This yielded a good 100g (8 oz) of mixed leaves. Of these, the baby spinach was the smallest but also the most robust; with the lettuce it’s hard not to damage the other plants because they are so closely spaced.

Was it Worth it?

Growing a living salad has been much easier than growing lettuce outdoors. No weeds, no pests, watering automatically through the capillary matting and the only thing that required time was harvesting and thinning.

As for cost, the two florescent tubes use 24W each. That works out at about 5kWh of electricity per week and a cost of around £3.50 ($5.50) over the six week period plus another £1 ($1.50) for the compost. I don’t count the cost of the seeds because they were leftovers from previous seasons.

For this outlay I harvested about the same quantity of leaves that I would get in a couple of living salad trays costing the same amount. More importantly the salad is still growing and I think the overall return will be about 3-4 times the cost of buying fresh living salad. On its own it would take quite a few batches to recoup the expense of the grow light system but since I had bought that for raising seedlings, growing salad in it is simply an added benefit. It’s expensive compared to growing it outside but at this time of year I can’t grow anything apart from small amounts of corn salad / mache and snow crushed my overwintering lettuce this year. It certainly satisfies my desire to get growing early and harvest something during long dark days! Overall, with the advantages of organic production and the benefits of fresh salad that hasn’t got thousands of food miles attached, this is one experiment I think I will repeat next winter. However, as soon as temperatures warm up enough to produce salad outside again, I’ll be switching back to growing in the greenhouse.

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Comments

 
"Great article! I'm experimenting with microgreens myself... and have a little hoop house experiment going too. I'm going to add a link to this article on my blog for future reference. I love the idea of having a "living" salad!"
Toni on Monday 31 January 2011
"How deep was the container you planted in?"
Pat Roloff on Tuesday 1 February 2011
"The containers have about 3 - 4 inches soil in them. With this kind of intensive planting the depth and quality of soil are very important."
Jeremy Dore on Tuesday 1 February 2011
"I don't understand how you wick water from a reservoir to the soil unless you have a growing container with holes in the bottom and a capillary mat under it??? I do think that would be a better way to water than overhead as how would you keep the tiny plants from toppling over if you watered from above. I am going to start some spinach indoors next week but would really like more information on the type of container you used. "At first I watered only from above but soon found that using the self-watering base with capillary matting gave much faster growth.""
Pat on Thursday 3 February 2011
"The trays do have holes in and the self-watering base is essentially just a reservoir tray filled with water with a platform on it (stands on short plastic legs). The capillary matting is over the platform and folds down at the edges into the reservoir. The trays stand on the capiliary matting which wicks the water up from the base to the bottom of the trays where the soil can absorb it."
Jeremy Dore on Thursday 3 February 2011
"Update: It's now about two weeks after I wrote the article and I have about the same amount to harvest again. I'll probably get one more cutting after that or several small harvests. The spinach remains quite small but the other salad leaves are a good size."
Jeremy Dore on Thursday 3 February 2011
"I enjoyed this post a great deal. Is there any chance you could show us a picture of the self watering base? What is "capillary matting?" I'm having trouble figuring out how I could duplicate this."
Bill Brikiatis on Thursday 3 February 2011
"I think you can buy capillary matting from garden supply catalogs. The matting must go from the water reservoir up onto a base that the growing container sits on. It wicks the water up onto that base where the plants can soak it up. What I don't understand what the bottom of the growing container looks like. It has to be solid enough to hold the soil in place but open enough for the water in the capillary matting to be available to the roots. Jeremy, I would love to see a picture also, especially of the bottom of the container. "
Pat on Friday 4 February 2011
"Pat - the trays are just like normal seed trays with small holes in them and that's enough to get the water to wick up. They're a little deeper than standard trays though. There's a picture of something similar with a diagram here on Garland's website (although the illustration shows pots not trays): http://www.garlandproducts.com/index2.php?option=com_smspu&image=f487d4de36f07771d5da639da4a3a448.jpg"
Jeremy Dore on Friday 4 February 2011
"Jeremy -- Thanks for showing the photo"
Bill Brikiatis on Friday 4 February 2011
"Excellent idea .I think what I may be inclined to do is skip the sowing of the seeds and get some of the trays of living salad from the super market and then put them in the tray system with lights. Instant salad and you know it will keep growing as the supermarket has done all the hard work in picking the correct varieties. Would works ok for Basil, Parsley etc. It does show now how we take for granted non seasonal veg out of season. 50 years ago it would have been just Kale and Leeks in Jan!!!"
Rob on Friday 4 February 2011
"WOW!! Great idea. I will sure look into that if I can find some decent living salad at the store."
pat on Friday 4 February 2011
"Again another interesting and informative article. "
Joe on Saturday 5 February 2011
"wonderful..blogging about this same subject Monday...love my grow light to help herbs and my seeds started indoors...gives them more light and strength so they will be viable...my lettuce took 2 days to germinate and is almost ready in 2 weeks time to start harvesting...will let it grow a bit longer...thx for the tips..they will be most useful as this project continues..."
Donna on Saturday 5 February 2011
"Cat litter trays are good if you need more depth of compost Many allotmenteers start their leeks off in these"
Vet on Saturday 5 February 2011
"Great advice on setting up the grow lights in the room upstairs, the extra heat rising through the house will certainly assist in speeding up the growth of the plant. Grow lights are avaliable at http://www.rotherhamhydroponicscentre.co.uk/Grow-Lights."
Andrew on Monday 10 October 2011
"A gal at the local nursery told me she grows lettuce inside during the winter so I though I would give it a try. I put them in the window and they sprouted fast but were not looking great. I moved them under the cabinets were I have florescent under cabinet lights. They were doing great but have died before I could harvest anything. I wonder what the difference between the lights is??"
Kelly on Monday 17 October 2011
"Grow lights emit a 'full spectrum' light which is what plants need and is different to normal fluorescent lights so that will likely be why the plants have not done so well Kelly."
Jeremy Dore on Monday 17 October 2011
"Just bought a Garland Grow Light Garden. I live in Arizona but my apartment's patio is always shaded and my sunny front entrance has no private area. I plan on sewing spinach, lettuces and radishes but am wondering what is the best potting soil brand to use? Any suggestions would be very welcome."
Nancy Pink on Tuesday 29 November 2011
"Hi, I have been trying to work with my grow lights and I have some success, but I do find gnats a problem, do you have any ideas about this? I find that little dishes of apple vinegar seem to keep the numbers down, but??? Thanks, Carolyn"
carolyn madison on Thursday 15 December 2011
"Yes, gnats or fruit flies can be a problem, although it's not a problem I experienced when doing this batch of salad. The key seems to be fresh sterile potting soil and clearing plants out of the room for a couple of weeks before starting. There's a good trap for fruit flies here: http://www.cobraheadllc.com/blog/2010/08/06/easy-fruit-fly-traps-or-die-bugs-die/"
Jeremy Dore on Thursday 15 December 2011
"thinking of buying a light garden information very helpful thanks"
Lesley Barnard on Saturday 28 January 2012
"After our discussion last winter I decided to give this a try. We have been enjoying fresh lettuce for three months. The only comment I have is that the lettuce is very soft, even though the mix of seeds I used contains mini romaine. I wonder why this is. Growing outdoors the same seeds produce a much heartier lettuce."
Pat Roloff on Saturday 28 January 2012
"I think I've just found a great site for gardeners. I've just bought two grow lights and am trying to find info as to how to use them. This site has just given me some ideas. thank you"
Posey on Friday 6 April 2012
"Pat Roloff might find her lettuce is crisper if she has a fan turned on for some part of every day. Commercial greenhouses always have air movement and I believe it keeps the plant cells more "challenged" and tougher. Even a small fan for an hour or two might help. Also discourages gnats."
Nancy Pink on Wednesday 11 April 2012
"Thanks Nancy for the suggestion. I will try that."
Pat Roloff on Wednesday 11 April 2012
"I bought a light garden mid february and i am delighted with it Have it in my attic and have grown several trays of salad and herbs Put seeding of peppers, tomatoes and flowers in it out of propagator and they have come on very well Had gnats so I have used Yellow catchers I open velux window most days for a while Having to move plants in and out so they all get a few Days in it wish it was biggger"
Lesley Barnard on Thursday 12 April 2012
"I am thinking of buying a growlight to bring on seeds early. How sucessful were you and can you give me any advice on timings for peppers and tomatoes in particular"
Janet James on Thursday 26 July 2012
"Janet, I bought the lights in April, and would you believe they are still in the boxes! Hubs did look the other day at where he might put them. He also said he has to check the power in the greenhouses to check the wiring is 'right'. I'm hoping they are fitted by Christmas! He is usually so quick to fit things but did ask if I knew just how much electricity they will use. I think that has been the reason for dragging it out. My peppers and cucumbers usually grow very well but I am hoping that they will come on far quicker, plus hoping to grow lettuces during the winter."
Posey on Thursday 26 July 2012
"Now is he psychic or does he hack my computer? Guess who is busy fitting the lights in the greenhouse?"
Posey on Friday 27 July 2012
"Perhaps he just tunes in to the same websites! Pleased things are moving for you although it is a bit late for this season."
Janet James on Friday 27 July 2012
"Yes, I know, I have moved just about everything out of the greenhouses now, other than cucumbers and tomatoes. I was thinking that it will be ready for early sowings next year. Also wondering if I will be able to grow some lettuces over winter thinking that a few extra hours of light will make a difference. I have a little stove in there also to give some warmth. Fingers crossed. I've just subscribed to Dig It as well, so hoping for some help and ideas from that. "
Posey on Friday 27 July 2012
"I started sowing Peppers , Aubergines , chillies in February Tomatoes in March Courgette's may all plants are doing alot better than last year will start using light box again in late autumn for winters salads and herbs "
Lesley Barnard on Sunday 29 July 2012
"I hung a couple of Bayer greenhouse fly catchers each side of the grow light garden to catch the compost gnats."
HP on Sunday 16 November 2014
"Jeremy, did you have any issues with the quality or construction of the Garland grow light garden you referred to in the article above? Would be interested as I was thinking about buying one as I find it hard to grow plants in my flat without them become leggy before planting in my allotment. However, I had read some mixed reviews about the Garland product (which seems to be the only one available in UK). Some reviews by purchasers commented on how difficult it was to move the lights up and down and it required 4 hands, some issues with bits not fitting well during the construction etc. I don't want to waste my money if any construction/usage issues outweigh the benefits Appreciate comments from you or other members/readers who have this product"
Sue on Thursday 2 April 2015
"Just purchased a Garland Grow Light for Xmas and already set it up for 2 trays of salad leaves which are already up. Appreciate Sue's comment from April so I will modify mine when I have stopped using it after growing my tomatoes, peppers etc. in the spring. The problem is the way the height is adjusted with what is little more than 2 elastic bands around the uprights. So what I will do is unassemble the unit and then drill small holes through the uprights every inch starting at the top but only as far as they go into the bottom tray. I will then use small metal or wooden pegs (small nails?) in these holes to hold the hood up. This will make it easy to move the hood up or down one inch at a time for each sides. Caution, don't drill too big a hole so as not to affect the integrity of the supports - 2mm should be enough."
Alan Corbett on Sunday 3 January 2016
"There is a retro fit height adjuster available from Garland which makes raising and lowering the hood much easier. "
Janet James on Friday 8 January 2016
"Thanks Janet that's very interesting - I am in contact with Garland to purchase the water tray and capillary matting (which was not included with my purchase) so I will add that to my list."
Alan Corbett on Friday 8 January 2016

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