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?
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.
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.