Growing lisianthus in Zone 3

As I saw the first tiny sprouts of lisianthus up in my basement this week, I realized I’ve been growing it for ten years. It’s a crop I truly enjoy for its showy, frilled blooms, the multi-flowered plants (10-20 on one stem!), and the long vase life. Many folks avoid seeding lisianthus because it has a reputation as being difficult. It is most definitely slow, taking up to seven months to produce flowers. That’s a lot of time for things to go wrong. So, I won’t tell you it’s an easy plant to grow. It’s challenging, but like all difficult things, when you succeed, you feel like a million bucks.

I started growing lisianthus from seed because I was looking for a rose substitute. In my Zone 3 garden, all the beautiful old-fashioned roses I admire are not hardy to our frigid winters. I loved the wide range of colors available in lisianthus and decided I needed this flower in my lineup.

In ten years of trial and error, I’ve learned what practices work best to grow healthy plants with an abundance of blooms.

The most important tip for cold zone growers is to start early. Lisianthus is a biennial native plant from Texas that ideally has a long cool winter between getting established in the ground and blooming the next summer. We can manipulate that timeline and get blooms in the same year, but only if seeds are sown early in January.

I start my seeds in 3/4” soil blocks for space-saving and sow two seeds per block. I use Promix BX and make sure the soil is very wet. Trays go onto a shelf under LED lights that are on for 14 hours. I use a heat mat set to cycle 30 minutes on, 30 minutes off to maintain about 25C for germination. Humidity domes are very important as all lisianthus seed comes pelleted. For the seeds to germinate, the pellet coating has to melt essentially. You can aid this with a fine mist sprayed every day, or just keep the soil very moist by bottom watering. If you mist the seeds, be careful not to knock them off the soil. They are tiny!

With this setup, my seeds start germinating in a week. I leave them in the same spot until I have about 90% germination, then I move them off the heat onto a cooler shelf and remove the humidity domes. They continue to get 14 hours of light but I keep the temp below 20C for the first 3 months of growth. It’s crucial to keep your seedlings cool at this stage or they will rosette and your lisianthus which should flower in 5-6 months will take 8 or 9 months to flower. I’ve experienced this and it’s frustrating to watch plants that look healthy and leafy just sit in the ground and not put up flower stalks until the end of October when the season is over. Remember, this plant is a biennial: the cycle of very warm temps, followed by cool temps, and then warm again makes sense. The natural cycle would be a seed germinating at the end of summer, quietly bulking up during the cool winter, and producing long stems as the days lengthen and the temps warm up again.

The ruffly beauty of Voyage 2 Champagne

When the seedlings grow to the stage of two sets of leaves, they are bumped up to 1.5” soil blocks. I don’t separate seedlings if both have germinated in the 3/4” soil block. I move my seedlings outside to my greenhouse as soon as possible, usually in early April. I protect them from the direct sun and gradually move them into the full sun as they adjust to the much brighter environment of the greenhouse. I’ve lost many seedlings to sun scald when I didn’t allow them time to habituate.

I start fertilizing my seedlings when they have the first set of true leaves. They get very dilute fish fertilizer every other watering when in the 3/4” block and every watering once they are bumped up to the larger soil block. Be careful not to over water the little seedlings. You don’t want them to dry out completely, but lisianthus prefers good drainage. If you are growing them in a cool environment to avoid rosetting, you shouldn’t need to water every day. I give them a RootShield WP treatment once as seedlings in soil blocks, again when transplanting them, and again in August. This helps prevent fusarium from killing my precious plants. Nothing is sadder than nursing lisianthus for 6 months, having a plant full of flower buds, and then finding brown, wilted plants the next day. Fusarium can wipe out 40-50% of your crop in a month. When I stay on track with my RootShield treatments, lisianthus is otherwise pest and disease-free for me.

I’ve grown lisianthus in raised beds and a hoophouse. I prefer my hoophouse because the extra heat and protection from the wind and rain produce superior flowers. If you aren’t looking for florist-quality blooms, your field or raised beds will do just fine. I plant lisianthus in the ground well before our last frost date as they want a cool start and are quite frost tolerant. I aim for May 1st or even the last week of April. If we get a cold snap, I throw some frost fabric on them but I have seen them handle -5C with no damage. I plant closely, with two plants per 6”. I use Hortonova netting as a planting grid and to support the plants as they grow. Lisianthus must have netting or some other kind of support around them or you’ll get wonky stems and snapped plants. If we’re having a good year with lots of hot weather and the plants are getting quite tall, we’ll put a second layer of Hortonova on them to keep them nice and straight as they grow. An important consideration for me is crop rotation so my lisianthus does not follow tulips in my tunnels. If tulips were in one of my 80-foot rows the year previous, lisianthus would not be planted there for three seasons. This helps keep the risk of Fusarium lower as tulips are often infected with it.

I do NOT pinch my lisianthus plants, but I will pinch out the first bloom on each plant. This first flower is a week or more ahead of the other blooms and pinching it out allows the other flowers to blooms together, giving the impression of a whole bouquet on one stem. I wait until 3 or more flowers have opened on a stem before cutting. I think my best stem had 12 flowers open at once! When harvesting, I cut the whole stem, leaving just the basal plant. This will encourage new stems to shoot up. I cut into plain water and tell customers to expect 14 days of vase life. They are such a long-lasting cut!

Lisianthus seed is labeled by bloom time from 1-4. According to the seed companies producing lisianthus, there are only a few weeks separating the bloom time of Group 1 from Group 4. In my experience, Group 1 and 2 varieties are the only ones that will bloom in my short season. Even if we have a nice fall and no killing frost until October, the sun has lost much of its intensity by mid-August. The Roseanne series has always been the earliest to bloom for me and the only one to consistently give me a small second flush of flowers. My other favorite series is Voyage. I love all the full ruffled blooms and the range of colors. I’ve grown a few Group 3 and 4 varieties and they were a waste of time and money.

When I get all my timings right and sow, bump up, and transplant at the correct stages, I can harvest lisianthus in the 4th week of July from seeds sown in early January. I will get a small second flush before plants are killed in October. If my seedlings rosette, it could be October before I see any blooms.

In summary, growing lisianthus from seed is a long but rewarding process. There really is nothing like them for their beauty, vase life and range of colors. I hope you give them a try.

Some of my favorite varieties:

Roseanne Terracotta

Blue Chateau

Voyage Light Apricot

Corelli Sugoi White

Corelli Sugoi Green