Gather seed capsules in the fall when they turn brown. Allow them to dry, remove the seeds and keep them in an envelope. In February, sow the seeds in a small pot containing 50% milled sphagnum moss and 50% horticultural perlite. Do not cover the seeds with the medium. The germinating mixture should be sterilized with boiling water and allowed to cool before sowing. The pot needs to be in a controlled humid environment. Polyethylene bags are great for maintaining a high humidity. The pot is placed in a polyethylene bag with stakes to keep bag away from the germinating seed and placed in a light area with no direct sunlight. The pot is rotated once or twice a week to compensate variations in light and temperature. Generally no winter chilling is necessary to get the seeds to break dormancy. Keep the seed pots or flats in the 65ðF to 75ðF range. The seed will sprout in from 3 to 8 weeks (sometimes longer) and after they have formed their first set of true leaves, they can be transplanted into other flats or containers. Since they are so tiny, they will not stand frost until they are larger and some months old.

When asked about growing Kalmia seeds, David Fisher of Wiscasset, Maine, wrote: "I recommend sowing the seed on top of live moss - this works for all ericaceous plants. I've generally used haircap moss, but any species should be fine.

Avoid peat pots - they wick away moisture from all the exposed surfaces and are very hard to keep evenly moist. Instead, use small plastic flats, surface sow and place in a ziplock plastic bag. Place under flourescent lights if you can, otherwise put in a bright spot, but avoid direct sun - high temperatures are fatal.

Root disturbance shouldn't be a big concern. Kalmia have dense fibrous roots just like rhododendrons so are easy to transplant. You do need to sow lightly and thin out the seedlings when small. The seeedlings will need to stay in the flats for probably 2 years. It's important to gradually remove the plastic bag, but you need to maintain a very humid atmosphere around the seedlings."

Here is a link that might be useful: How to raise Azaleas from seed