Yes, it is possible, but not all balconies are suitable, and it’s up to you on how much space you are prepared to give up, and also how much sun your balcony gets.
Bearing in mind your balcony is probably a wonderful haven to sit for breakfast in the morning or hang out your laundry on a sunny day (or even somewhere to sit and have a sundowner of an evening depending on which way your balcony faces!), you need to plan how much foot space you are prepared to give up for container gardening. Leave yourself room for the table and chairs so you can still sit out and enjoy the view, if that’s something important to you.
Root vegetables, such as beetroots, radishes or even potatoes can be grown in pots, but they will need the biggest pots you can accommodate and a good deep growing medium. The pots need to be straight-sided if the plant grows a lot of foliage, as canes might be needed for supports, and slope sided pots won’t be stable enough. Adding a slow release fertiliser or a water retaining gel will help your crop too.
Tomatoes are probably the easiest to grow in pots, and there are varieties that are even suitable for hanging baskets as well, but your baskets must be sturdy enough to hold not only the soil but the crop when they start to fruit. If you go for the hanging basket idea, make sure the basket has a good strong wall anchor, and chose a cherry type tomato such as ‘Tiny Tim’ or ‘Tumbler’, the first has 2.5cm fruits with good flavour, and the second has compact vines that can produce as much as 2.7kg of fruit in a season.
Other veg to consider are beans, peppers and peas, however, some of which will probably need supporting canes or trellis too, so if you can, have them grow against a wall where you can attach a trellis if necessary.
There are many types of herbs you can grow in containers, and you might want to consider railing planters to save on your space, which means you are freeing up space for more pots underneath.
Mint, oregano, parsley, basil, thyme and coriander are some of the most popular (and useful to use fresh!), and will all do well in a sunny spot, but be careful which ones you plant together, as some like sandier soil and others prefer moister soil.
Lettuces are also a veg to consider growing in a container and offer easy access when you want some leaves for a salad. However, they prefer a cooler spot and a consistent supply of water as they are almost 95% water, but won’t tolerate soggy roots. A clay pot with good drainage is perfect for them as the clay will help evaporate any excess water.
Lastly, if your balcony is above someone else’s space, please take special care when watering! If you can find trays to fit under your pots and containers it will save a lot of water running off onto your neighbour’s balcony, especially as some of that water may not always be clean. Your neighbours won’t appreciate your dirty water dropping onto their freshly washed laundry!