Basil thrives in Earthboxes.
I grow it from seed, starting it indoors on a heatmat, then raising the seedlings under lights until they are ready to go outdoors.
Be careful not to set them outside too early, basil does not like cold weather.
Above is a photo I just took today of my basil. There are six plants in this one Earthbox, which is the official recommendation and it is indeed the perfect number, in my opinion.
As you see in the image, the plants are full and bushy.
We want full and bushy basil plants, not thin and spindly, and the way we get our basil bushy is to trim the plants frequently. You start when they are young, and keep it up throughout the growing cycle. Early in the season, it is a treat to get the small amount of trimmings. Later in the season, you very likely will not even be able to use all the cuttings you take. You should still keep it up, because if you don’t, you end up with thin plants that bolt sooner.
When I have a surplus of basil I dehydrate the basil in my Excalibur dehydrator to have it for the winter months. When you dehydrate the leaves, do it at a very low temperature, no higher than 95ºF. This retains the potent flavor. Turn the heat higher and you will end up with lackluster basil with much of the wonderful flavor lost.
Before I had a dehydrator, I froze the basil. I found the best way to do this was to put a thin layer in a zip lock bag, and carefully squeeze as much air as you can out of the bag. A nifty trick to get the air out is to stick a straw in the bag, seal it as much as possible and then suck the remaining air out, then pulling the straw out and quickly zipping the bag up.
Back to the trimming. How do you know where to trim exactly. The plants actually make it very easy for you. Basil leaves grow in sets of two right across from each other on the stem. Take a look at your basil plants, and you will see two sets of tiny leaves growing out of the junction. When you’re trimming and harvesting, you should make the cut directly above one of those sets of leaves. Every time you cut the stem right above a set of leaves, you halt the growth of the main stem and instead two new stems start growing. This is why trimming this way leads to lusciously thick and bushy plants. One other thing: it does not have to be the two sets of leaves at the very top of the plant, especially as the season progresses, you will instead chose to cut at a lower intersection, in order to create fuller, bushier, healthier plants.
See image below for where you want to cut the stem: