3. Use fresh, good-quality, indoor potting soil. Place 2.5 to five centimetres in the bottom of the pot, then add enough soil for the noses of larger bulbs such as tulips, hyacinths and daffodils to show just above the final soil level, which is 2.5 centimetres below the pot's rim, leaving room for watering. Adjust the soil level for smaller bulbs (such as grape hyacinths and squills); their tops should be covered by one centimetre of soil.
Position bulbs such that they're almost touching each other. When planting tulips, face the flat sides of bulbs toward the pot's sides; the first large leaf emerges from the flat side, so you'll avoid congestion in the centre of the pot. Water well. Label pots indicating bulb type, planting date and when to remove from cold storage.
4. Place pots in cold storage. A refrigerator is ideal for forcing because you can control the temperature; but don't place bulbs in a fridge containing any ripening fruit, which produce ethylene gas and can damage emerging flowers. Other options include a Styrofoam cooler, a garage, a trench in the ground (covered with sand or leaves) or a mulched cold frame. Having the right temperature is the key to success—begin by adjusting the refrigerator to 15°C (or the warmest setting). Then each week reduce the temperature by 5°C until the coldest setting is reached.
Check the bulbs every two weeks to make sure they're moist and no extensive moulds are growing. A few small patches of mould on the soil are tolerable, but if they start to cover most of the soil surface, sprinkle with a fungicide containing powdered sulfur.
5. Once the cold treatment is completed, it's time for the bulbs to finish growing and forming their blooms. A cool (15°C is ideal, but anything below 20°C is acceptable), bright location is best for this stage. Bulbs typically bloom in three to four weeks after being removed from cold storage.
6. Because forced bulbs use a lot of energy to produce blooms in a short time, they're best treated as single-use. But continue to water them once they bloom and, when there's no risk of frost in spring, tuck them into the back of a border. They probably won't flower the following year, but with a bit of luck, they may offer you another splash of spring colour the second year.