The leaf and the rhizome can both be used.

Did you know that you can use the leaves of the turmeric plant in your cooking?

A couple of years ago, I started experimenting extensively with Asian food. Whenever Planet Food featured an episode on Asia, I ensured that I didn’t miss it. One such episode introduced me to the idea of cooking with the turmeric leaf.
Though manjal or haldi — as turmeric is known in India — is used in most traditional recipes, the leaves weren’t easily available in the market. Grocers asked me to wait until the harvest season. That’s when it dawned on me that the only time we used the turmeric leaf was during Pongal festival when we tie it around the mouth of the pot.
Luckily, a grandaunt sent me a few rhizomes for me to plant. It took some time but the tiny green shoots were not as lush as I expected. So I soaked the second lot in water until they sprouted and then planted them in moist soil, which received medium sunlight. It took about 10 days or more before there were any signs of activity. But once it started, the speed at which the plants grew was amazing.
In the coastal regions of India, turmeric leaves are propagated and used to make herbal concoctions to ward off cold, fever and other respiratory allergies. In Goa, turmeric leaves are used to make a rice dish called Patholi. A paste of rice flour and water is smeared on the leaf. Then a mixture of coconut, jaggery, cardamom and a pinch of salt is spread in the centre. The leaf is folded and placed in a steamer. The leaf’s aroma intensifies as it cooks and the plant’s anti-bacterial and anti-fungal properties seep into the food.
Countries like Indonesia and Thailand also use turmeric leaf parcels to steam fish and delicate seafood. The lead needs to be soaked in water or pressed down gently in the middle to make it more pliable for folding. In Malaysian cuisine, turmeric leaves are torn lengthwise into tiny shards from the tip and added to dishes like lamb rendang, Manado chicken (ayam garo rica) and soups.
This is how I first used the turmeric leaf by adding it to a Thai chicken dish. The taste was subtle and delicious. The leaves must not be sliced with a knife. It’s best torn and added towards the end of the cooking process. The distinctive smell of turmeric permeates your hand. The only thing missing is the trademark yellow colour. Many Westerners prefer to use the leaf, as they get the taste of turmeric without staining their garments while cooking. Last week I added it to the South Indian molagu thanni, or rasam. It goes well with the spice from chillies or peppercorns.
The golden-yellow rhizome is very popular and is sometimes referred to as ‘Indian saffron’. This is largely incorrect. Due to cost factors, turmeric is substituted for saffron only for the colour. They bear no similarities either in taste or characteristic. The turmeric belongs to the ginger family and has similar medicinal properties.
My turmeric plant is now lush and green. The flowers from the plant are also included in exotic dishes. It’s not difficult to grow your plants. They grow well in pots or grow bags. As I wait for the flowers to make their appearance, the leaves are being added to my cooking pot on a regular basis.
Read more about food at Shanthini's blog www.pinklemontree.org
Quick facts
Its botanical name is Curcuma longa. Once the plant flowers, it can be cut to the base to encourage new growth. When the leaves turn yellow, it’s time for the rhizomes to be harvested. Cover with sawdust or dry peat and dry them in the shade. Turmeric plants are very hardy. Even after a spell of drought, the bulbs can be dug up and harvested.
Turmeric powder
Clean the rhizomes thoroughly. Boil in water for 45 minutes. Drain, peel skin and let dry in the shade for about 10 days. Pound it before powdering with a pestle and mortar or in a blender.

Source : The Hindu