Make sure that if you plant to use your containers outdoors that the plants you include have been hardened off. “Hardening off” is the process of moving plants outdoors for a portion of the day to gradually introduce them to the direct sunlight, dry air, and cold nights. You start with a few hours in the shade, then a few in sun and shade then longer periods of time outdoors until they can finally tolerate the flexible outdoor temps. If you spring the outside on them the plant will often die. So give your plants a fighting chance by hardening them, especially of they came from your grow lights or from a greenhouse nursery.
Step to planting:
Fill your container with soil mix. The amount of soil you put in depends on whether you use seeds or seedlings to plant your herb garden. In general, if you are using seeds, fill your container to about 1 inch from the rim so that you will have room to cover your seeds with a little additional soil.
With plants fill 2 to 3 inches in the bottom, place the plants and fill in around the plants. Make sure the soil is well firmed down to give roots more hold. Peat based soil (often times called growing medium) is better suited for growing seed, not large living plants. It dries out more quickly and lacks much nutrient value.
Mix nutrients into your soil - It took me years to realize that I was starving my plants to death. Use a manure-based compost or a home made compost that you mix into the soil mixture you use in your pots to provide nutrients, then realize that the soil will become depleted over the season and feeding will be required. You can make a compost tea or purchase a commercial fertilizer. I water with compost tea once a week when we reach the height of the growing season in late June (see below for a link to a fertilizing post.)
Make your own potting mix by blending:
I also found this recipe among my lecture notes. I have tried both and have no opinion which is better. I like using coconut coir instead of peat moss because it is more renewable.
Planting - There are two main things to know when actually planting a plant in a container (or anywhere else for that matter). You want to plant it at the same level that it sits in its nursery pot. So in other words, the level of the soil should stay the same and no more or less of the plant's stem or crown should be covered. You also want to make sure there are no air pockets and your plants' roots are surrounded by soil. In a crowded pot, sometimes it is difficult to put soil in between the plants, but you will need to make sure that you do, or the roots will dry out if they are in an air pocket, and your plant can die. Sometimes you just need to feel around a crowded pot and stuff soil into any holes you feel. It's also a good idea to water a pot right after you plant it, which settles the soil. At that point you can go back and fill in any holes or depressions with extra soil.
Give your containers a good watering!
Position pots of sun-loving plants where they will have at least 5 or six hours of strong light every day. Without that number of hours stay with bay, lemon balm, mint, parsley, thyme and scented geraniums.
Watering - watering of container plants is a daily requirement if they are in the sun. Twice a day (morning and evening is ideal). About 1/2 to 2/3 through the growing season the soil will become depleted of nutrients so prepare in advance to have a fertilizer at the ready to add to your watering routine to keep the plants healthy. For more details on fertilizing containers, check out this blog post from 2013.