Answer: Many plants, including most common bulbs, have an annual cycle of growth and rest. The hardy spring-bloomers you mention (tulips, daffodils, crocus, and hyacinths) rest during the hot summer and cold winter, and won't wake up until spring has arrived. The mechanism for this is the need for a certain number of chilling hours to break dormancy.
If your cold-hardy bulbs don't get adequate chilling (6-10 weeks at near-freezing temperatures), then they won't bloom.
Since you live in a mild winter climate you can provide the bulbs with their required chill by placing in the refrigerator for 6-10 weeks, then planting outdoors.
Iris doesn't require any special treatment and can be planted now (if you have the rhizomes) or in the spring when they become available through catalogs or garden centers.
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