Sources: I’ve found seeds of various succulents, mainly Sempervivum, in seed catalogs in addition to their selection of all kinds of other perennials and annuals. Look carefully as they sometimes are hidden under some kind of category like unusual plants, greenhouse plants, alpine plants or something else.
Of course, you can also save your own seed from rosettes that bloom. Keep in mind that all these seeds will be insect pollinated, so depending on the types that are blooming at the same time, the resulting seedlings will reflect many different parents. This is a good thing – this is how new varieties are made.
How to plant the seeds: Sempervivum, Jovibarba and the other types of hardy succulents don’t usually need or benefit from a cold period (called stratification) to start germinating, so you can plant them in a communal flat immediately after you receive them.
I wait until the weather is fairly settled in the spring and there isn’t the chance of a hard freeze any more. Overnight low temperatures are fine, with daytime temperatures above freezing.
Prepare your flats – I use a 1020 open flat which is half filled with sterilized Sunshine Mix #4 which has added aggregate to drain better. It also has a water retaining polymer to hold more moisture, so the flat won’t dry out. There is nothing more difficult than re-wetting a dried out flat of peat based soil mix. I also put a thin layer of turkey grit on top before seeding to make it easier for the seeds to find a moist place to germinate. This also stops the growth of moss or algae, which can choke out the seedlings.
You will usually get a lot of fine dust like seeds in the package,
and if you’re in luck, they are double packed, with a smaller glassine envelope inside the larger seed package. This makes it easier to evenly distribute them in the flat.
I press a stick into the soil so there are three or four rows. This makes it easier to take the tiny seedlings out when they grow enough. Sprinkle the seeds very thinly by pinching a tiny amount with finger and thumb. The more uniform the seedlings, the better they grow, so avoid large clumps as this will stunt the growth of any that are crammed together.
You can also mix the seeds in with some other fine material like sand, to make it easier to get a uniform spread. Water gently with a fine sprayer, then cover with a clear plastic dome. I’ve had the Sempervivum and Jovibarba germinate within a week, but have patience, sometimes it takes longer.
Water as needed if the soil mix gets really dry. The important thing is that the air is humid until germination takes place. A light feeding of compost tea once the tiny plants have their second set of leaves will give them some nutrients until they’re big enough to transplant.
Transplanting: I transplant the tiny plants into 2 inch pots, which will give them enough root room to get a good start. They will stay in the 2 inch pots until the following spring, and they are wintered outside where they get covered in a foot or two of snow to insulate them from temperature fluctuations. Avoid watering them too late in the season, as the action of freezing and thawing on the roots will kill them. They survive much better if they are allowed to dry out a little before winter arrives.