I've never grown lisianthus from seed for exactly that reason. I've heard that the little plants I get at the nursery are already seven months old when they first appear for sale. Wonderful flowers, but very slow to germinate and get going.

Yes....that's normal. Lisianthus are tender perennials, not annuals. And greenhouses that offer blooming sized plants for sale in the spring started them the previous summer. That's why they are so expensive!! They need a long time in the greenhouse.
Linda C

Ahhh! That explains it then. The trouble is, I have never seen them at the nursery. What does that mean they are tender perennials, not annuals? What winter temperatures can they withstand?

A perennial is a plant that can live for years....they bloom, set seed and slow down to bloom again another day. Usually a perennial has a "season of bloom" and the rest of the time it's just a plant.
An annual grows and all it's energy is pointed toward setting seed....it you cut the seed pods off it will bloom again and continue until frost or old age kills it.
Lisianthus are an African plant, that would live for several years, unless something kills it....like cold weather.
Petunias and pelagaroniums are also tender perennials.
Linda C

Thanks- I just have never heard the term tender perennial- I have always only heard perennials. So, Lisianthus, given the right climate, would go through the stages of a perennial, not an annual, whereas annuals would only live one season regardless of the climate- is that correct?

Well...now that I have looked it up...my book says there are species that are annual, biennial and perennial...none frost hardy.
But what you said about annuals is correct.
Linda C

Lissys are a tender perennial. They are a hybrid created from the native priaire gentian native to Texas. Like all gentians they are very slow. I started them in October and they are still not ready. They dont like to be pot bound and dont like to be over watered. Addition of calcium and magnesum help the groth prosess. They are expensive because they take sooo long to grow but are very popular in the cut flower industry.

Lisianthus can be sowed even in March in Texas, and they would bloom around October/November, when other flowers have faded. The secret is patience! I personally don't see why people put in such a frustration with Lisianthus plants. Every plant has its own blooming period. If Lisianthus blooms almost at the end of the year and remain a small seedling until almost the end of the summer, just deal with that. They are worth all the months you will be waiting.

I grow lisianthus some years, and yes.....it takes a long time to grow them from seed, and is one I start months before the other typical bedding plants.

As to being pot bound, within each variety (and some are tall, and others genetically more dwarf), what size container or cell they are grown in can impact blooming time and maturity time. As their roots hit the pot sides and they start to become potbound, they'll stop growing vegetatively and begin to rosette. The ones I have growing this year are a tall cutting variety and if I want them to hit their potential with long stems, I can't let them get rootbound in their transitional growing-on flats.