Catnip can be used for more than just love affairs
"Catnip is ruled by Venus. Its element is water and its energy is considered feminine. Catnip is attributed to the Egyptian goddess Bast/Bastet, the cat-headed goddess.
Powers: cat magic, love, beauty, happiness
Magical uses: Given to your cat, catnip creates a psychic between the two of you. It is also intoxicating to the cat.
Catnip is used in love sachets, usually in conjunction with rose petals. If you hold catnip in your hand until it is warm, then hold anyone else's hand, they will forever be your friend, as long as you keep the catnip you used in the spell in some safe place.
Grown near the home or hung over the door, catnip attracts good spirits and great luck. Catnip is also used in spells designed to enhance beauty and happiness.
Large catnip leaves are pressed and used as bookmarks in magical texts.
Catnip has a lot of non-magical uses as well, besides intoxicating Kitty. I was interested to read that the oil isolated from catnip by steam distillation is a repellent against insects, particularly mosquitoes, cockroaches and termites. Those of you who know me know how I feel about cockroaches! I can barely type the word without shuddering. (And here I am applying for jobs in Georgia!)
For Kitty, one must know that about 2/3 of cats are susceptible to the chemicals in catnip. According to Wikipedia, this phenomenon is hereditary, and cats in Australia, for example, are not affected by catnip. Netpetelactone is the chemical produced by the plant.
Now, for us humans, catnip also has benefits. When taken as a tea, catnip reduces fever, and also helps relieve the symptoms of respiratory infections. A cup of hot catnip tea is also a good way to get a good night's sleep. Ladies, if you are having serious menstrual cramps, a cup of hot catnip tea will help ease some of your discomfort, as well a tea made with red raspberry leaves.
Catnip Tea:
Bring 1 1/2 cups water to a boil. Remove from heat and add 1 teaspoon of fresh catnip, or 1 tsp. of dried. Let the mixture steep for about 20 minutes. Add honey to sweeten, if desired.
More information on catnip can be found here: http://www.herbs2000.com/herbs/herbs_catnip.htm"
From http://witchininthekitchen.blogspot.com/2008/05/catnip.html
Any of these should be a good substitute: Bergamot, Chamomile, Galangal (Low John), Hydrangea, Licorice Root - (Quit Smoking), Slippery Elm, Fennel, Hawthorn, Peppermint, Knotweed
I think catnip leaves might have a slightly different signature - but so slight as the flowers and leaves could be used interchangably in my opinion. I love using flowers in my workings - they have a decidedly feminine and tender vibration.