Whether planted in pots or the ground, be sure to keep the flower buds pinched back to keep them from getting rangy and going to seed. Given the proper conditions, you should be able to harvest leaves until the first frost (if outdoors) or all year long, if in pots inside. You can start using the leaves, a few sprigs at a time, once the leaf stems reach 4" tall.

Marjoram leaves are best used fresh, as their flavor is sweeter and milder. For this reason it is also best to add them at the last moment when you use them for cooking. Marjoram has a slightly mintly, citrusy taste. Use marjoram's fresh taste to enhance salad dressings, seafood sauces, soups, and poultry. A chicken that has been rubbed with garlic, salt, course black pepper and marjoram, then grilled makes a quick and delectable summer treat -- one of my favorites. Marjoram's flavor also works well with cheese, tomato, bean or egg dishes. Marjoram is most often used in recipes of French or English origin, whereas oregano's more robust flavor is often called for in the recipes of Italian, Greek, North African and Mexican cuisines.

[from Linda Gilbert's Oregano...or is it Marjoram?]