Figure about six to eight daffodil bulbs to an eight-inch pot. Many greenhouses use six inch pots, but we find these smaller pots just too cramped and messy when watering. Larger containers may be used and make an impressive display, but be mindful of the weight, you will be moving these around later!
Before potting, store the bulbs between 60 and 70°F with plenty of air circulation. This is important.
Some gardeners recommend soaking the bulbs for 24 hours in a rooting hormone before planting to encourage root growth. This may be advisable , but we have never tried this.
Fill the bottom of the pots with gravel, and then halfway with soil. Adding about 20% sand is good for drainage and will discourage mold and bacteria. Sterile potting mix is not better than soil from your garden mixed with sand and peat moss. Place the daffodils and cover with soil so that the noses of the largest bulbs are just showing at soil level. Water thoroughly, don't bother to fertilize.
The containers need to be kept between 35 and 40°F for a minimum of 14 weeks. If you can maintain this temperature exactly and all conditions are perfect then 14 weeks will be enough, but realistically plan on 15 to 17 weeks of dormancy. If the temperature goes to 45°F occasionally that is OK. Protect the containers from prolonged periods below 32°F, if they freeze through the bulbs will be killed. Bulbs in containers are more sensitive to frost damage.
Here are three ways to hold the containers at temperature during dormancy:
Keep the containers in a cooler or refrigerator at about 35 - 40°F. Never store bulbs with fruit, in that the ethylene gas that some fruits give off will damage the flower inside the bulb. You will need to provide water to keep the soil humidity high. Always water thoroughly.
Keep the containers in a garage, basement or crawl space that is generally within the temperature range. We know of a cemetery foreman who manages a large amount of containers in a crypt. So a crypt is good also if you have one handy. During this time you will need to provide water to keep the soil humidity high. Always water thoroughly. Remember that you need to protect the containers from freezing through during the dormancy period. This should be fairly easy in zone 7.
Bury the containers outside under four to six inches of soil. You may also stack the containers in a mound, cover them with 2-3 inches of sand and then four to six inches of straw. Salt hay is a good covering too, but lately it seems that salt hay is hard to find and expensive when you do. A trench for the containers will reduce the amount of sand that you will need, we have found that the price of delivered sand is also getting expensive. After the digging is done this method is fairly easy in zones 5 and 6. In zones below that make sure that there is enough insulation to prevent freeze through.
At the end of the dormancy period, check the containers to see that there is good root growth. There should be visible top growth also. Move the containers to a lighted area at about 50 - 55°F for two weeks then to their final, well-lit destination. At 60°F + daffodils may start to bloom immediately. Some varieties will take another two to three weeks. Keep well-watered but reduce watering when the buds start to show color.