Growing from a seed
Mesclun salad is something we eat a lot of, and it is a very easy set of plants to grow. Mesclun is a French term for a mix of lettuce greens and typically includes chickory, arugula and endive (from diynetwork). Plant the seeds in a seed planter atop a few cm of seed raising mix, then cover with 0.5-1 cm of seed raising mix. You can plant a few seeds in each seedling container, although the more you plant will mean you will have to re-pot earlier. The seedlings will sprout within a week and within a few days will develop into two-leaved seedlings.
Find a spot that gets some sun; I choose afternoon sun as it is a bit more gentle on the seeds than the morning sun. Then water well. These seeds like a lot of water and they like the soil continually moist. Just think, lettuces as a plant hold a lot of moisture in their leaves, therefore they need this as plant babies to be able to develop their delicious moist flavour.
Gently water the seeds and seedlings daily, you will only need a few drops and water the seedlings from the bottom of the plant where possible, right next to the soil. The seedlings will topple over, or become intertwined as they start searching for the sun. Don’t get worried about this, they will sort themselves out. Be very careful when watering not to break the stalks.
You can use the baby seedlings in salads as micro-greens, but this will prevent your plants from growing new leaves. For this reason, I let them grow to their full potential. Personally I do not think that mesclun seedlings add much as a micro-green. You would be better off using young rocket leaves or mustard lettuces.
Once the seedlings have developed a bit further and the majority have two to three sets of leaves you can re-pot into an oblong planter box. I find the oblong shape perfect for these types of plants, especially if you have grown them in a 4-8 compartment seedling tray. You can at this stage space the plants out a bit more. However, they will still not need a lot of extra space initially. Usually at this stage your seedlings can go outside. Just make sure that there is no threat of frost, and the daytime temperature is quite temperate to warm, and the nights don’t get too cold. Your seedlings will struggle otherwise. Depending how hot the days are your plants may need watering twice a day at this stage.