For those of you who have a balcony or patio, you can grow anything! Provided of course that you have enough sun. Sadly, if you do not have enough sunlight, at least six hours per day, you will not be able to grow vegetables or most herbs. The acception is parsley and chervil, both can handle some shade. Otherwise you will be limited to some shade loving flowers and plants known for their greenery. But what flowers and greenery! I have seen some lush planting in deep shade turning an average balcony into a garden of delights.
First, if you do have sun, don't forget vegetables and herbs. They can be lovely to look at as well as tasty. Most types of lettuce and other greens such as arugula, cress (garden not water), mizuna are very easy to grow in window boxes. You will have too many seeds but if you start early enough in the season (like now) you can have successive sowing and always have some lettuce and salad greens on hand. You will need to constantly thin the seedling, but they are great tossed on a salad or in some pasta. Greens do need to be watered and kept from drying out, but have well drained soil so it won't get soggy roots. Remember that greens are for eating so don't use regular old potting soil with chemical fertilizers in them. Use organic potting soil and use liquid fish or kelp fertilizer or add compost. Better yet, make your own by mixing a bag of topsoil with a bag of compost. Add a few scoops of perlite to help with water retention. Most plants will do well with the organic materials in the compost, and benefit from a little fertilizer when they have 4 true leaves. Heavy feeders such as squash and tomatoes may need a second feeding when they start to set fruit. When in doubt first do no harm. Chances are if the plants look peeky it is because they have too much water that won't drain, or uneven watering. Tomatoes are a common vegetable for pots but surprisingly there are other veggies that may also do well. Beans make a lovely edible vine, particularly if you choose a type that is purple or yellow or mix them together.
Herbs like well drained soil also perhaps with a bit of sand. They can dry out a bit between waterings, but like all plants in pots when it is very hot they need water every day. A fun way to have several types of herbs is to plant a strawberry planter with a different type of perennial herb in each hole. For the top of the container grow something that is tall such as a bush rosemary or mounding parsley. Use creeping or prostrate plants for the side holes. You may need to turn the pot occasionally to get sun to all of the herbs, or plant parsley on the shady side. For annual herbs such as basil, keep that in its own pot, a large one if possible. You may want to plant mint in its own pot too since it can be very invasive.
For shade impatiens and begonias are classic choices but you can also use some small heuchera and hostas, calladiums, coleus and ferns. The rhyme to remember for a container garden is, "A thriller, spiller and filler". The thriller is something brightly colored or large and spikey, anything attention getting. The spiller is a vine or hanging plant such as sweet potato vine or ivy. The filler is something that does just that, fills in the empty spots. If the thriller and spiller are flowers I like the filler to be something with variegated foliage such as sedum, or if the thriller or spiller is foliage heavy I like to fill the container with a flowering plant such as million bells.