It is hard to say who is the most excited about Lisianthus: growers, florists, or the end customer of these stunning flowers. Though the slow-growing Lisianthus can be challenging to start from seed, you can raise a profitable crop and save yourself time, space, labor and a river of tears by starting lisis from plugs. This Lisianthus primer contains everything we know about planting and growing these highly marketable flowers.
History and Development
Lisianthus has gone from a relatively unknown American wildflower to a commercial crop of international economic importance in a remarkably short period of time. Back in the 80's a group of American academics and plant breeders recognized the potential of this pretty purple wildflower and set the stage for the explosion of varieties we see today. Japanese breeders such as Sakata, Takii and Sumika have further transformed this species into a wide range of flower colors, shapes and sizes with broad market appeal.
What's so great about Lisianthus? In the early days everyone was excited about a rose-like flower that could be grown as an annual and didn't have thorns. It also comes in blue and purple shades, which have long eluded rose breeders. With time the flower forms have become larger, more double, and more ruffled, making them a compelling focal flower. We are now seeing a new range of small, spray-type single flowers with a less formal "wildflower" look to them. The fact that they last 2-3 weeks as a cut flower has certainly helped with their popularity.
In the Wild
The best way to learn about a cultivated plant is to look at its wild habitat. Lisianthus is native to a wide range of North America, from Northern Mexico into the Southern United States: from Florida west to California, and north in the interior to Montana and South Dakota. It generally occurs in prairie or plains type settings, but most often in close proximity to stream beds and seasonally marshy areas. All of this tells us that Lisianthus is adaptable to a wide range of conditions, but needs a good source of water at certain times in its lifecycle. In the wetter and cooler times of year wild Lisianthus seed germinates and gets established. It has very deep roots so even in the dry heat of summer it can find moisture deep in the soil to keep it growing and blooming. This tells me that we need to make sure Lisianthus has plenty of water when it is young, and then can be less concerned with watering as the season progresses, assuming there is at least some moisture in the deeper parts of our soil. The broad geographic range also tells me Lisianthus is tolerant of a wide range of temperatures. In the wild, Lisianthus can become a short lived perennial when conditions are favorable.
Lisianthus seed is one of the tiniest of all commercial cut flowers. This is why it is almost always supplied as "pelleted" seed. There is an entire industry devoted to coating seeds with various materials to make them easier to handle, and Lisianthus is a prime candidate for such treatment. Large seeds tend to produce plants that grow quickly (think of sunflowers or pumpkins) whereas tiny seeds tend to need a long time to build up strength. This is part of why Lisianthus is notoriously slow to grow. It doesn't have many carbohydrates to get it up and running at the beginning stages of life. These tiny seedlings are also quite delicate, and one bad day can kill them. This is why so many of us rely on plugs rather than growing our own lisianthus from seed.
It needs perfect conditions every day for about 12 weeks just to get it to the small plug stage that we receive each spring, and these conditions are tough to create in the home environment. Thankfully, the conditions at Gro 'n Sell are just right. If you haven't tried to grow Lisianthus from seed, I encourage you to try it. You will appreciate your plugs more than ever!
The next critical stage in the life of Lisianthus is when it is transplanted. When your plug tray arrives at your door, the plugs are ready to go into the ground, or into a bigger cell. Don't hold them for more than a week, as they can and will become rootbound and will be stunted later in life. Order your plugs for a date when you know you will be able to plant them directly into the soil. All of our plugs are grown to order, and we've established that they take 12 weeks to grow, so make sure you order them 4 or 5 months before you intend to plant them. This gives us plenty of time to source seed and schedule bench space to grow your trays specifically for you.
So when do you transplant lisianthus for the best results? The only rule is that Lisianthus wants to start life in cool soil. This mimics what it experiences in the wild. They do best when given 2-3 weeks where soil is below 55F before summer conditions warm up. During this period they need to be gently but thoroughly watered with a sprinkler or a hose from overhead to make sure the plug is making good contact with the soil and is receiving the water it needs. Lisianthus is tolerant of frost when it is young, and will be fine with temperatures down to 20F, assuming it is planted in the ground. A tray above ground will freeze solid at 20F damaging the roots and killing the plug, but in the ground, those roots will be insulated. Your last spring frost date is an important benchmark in your season. Lisianthus should be planted out 2-4 weeks before your last frost date when growing in the field, or 4-6 weeks before that date if you are growing in a tunnel. Everyone's conditions are different, but just remember that cool start requirement and ample water in the early weeks and you'll be safe. Using a remay-type frost blanket is a great way to help your plugs adjust to the real world.
Lisianthus can be planted quite close together. I recommend 8 per square foot. If you are using standard 6x6" support netting, just use that netting as a planting guide and plant 2 plugs per square. Soil type is not hugely important as long as the structure of your soil allows the roots to make good contact and your soil is not soggy. Wild Lisianthus often grows in sandy conditions, whereas I have grown it on amended heavy clay for years with good results. Get your soil tested and amend it towards a neutral pH and general fertility. We always use plastic mulch to keep weeds down, but if you are a dedicated and obsessive weeder feel free to grow in bare soil.
I recommend using 2 layers of support netting with Lisianthus. When it has ample water and is transplanted at the proper time, Lisianthus can easily reach 3-4' in height. These tall stems with large heavy flowers topple easily. I have friends that don't use support netting and I am deeply suspicious of them!
Once your seedlings start to grow, you're nearly in the clear. Irrigate as needed, keeping the soil slightly moist. The larger the plants get, the deeper their roots have grown and the more tolerant they will be to drought. This said there is no reason to withhold water if you have sustainable access to irrigation water. Drip irrigation should do the job once the plugs are established and growing. Overhead irrigation is only needed for those first couple of weeks. Once they are up and growing they are very tolerant of heat as long as they are accessing water somewhere in the soil.
As the plants grow, move the support netting up with them. It is always better to slide it up before the plant needs to be supported, and it is a real pain to move netting up after plants are already leaning. I have made this mistake enough times to last a lifetime.
Lisianthus will initiate buds when several criteria are met. It must be warm enough (general summer conditions are warm enough), it must be receiving "long days" like we all have in summer. It must be receiving enough light intensity, again, easily provided in summer. The plant must also be mature enough, and this last one is a little hard to define, as it varies by variety. Lisianthus will not flower in the plug tray like some plants will, it must reach a certain stage of maturity before buds will form. We all recall the "early bloomers" in school when we were in our adolescent years and this is a good analogy. Just like humans, some Lisianthus varieties are genetically programmed to enter their reproductive phase earlier or later than others. Group 1 Lisianthus will enter their flowering stage (reproductive stage) earlier than Group 2 plants, followed by Group 3 and Group 4. By planting some of each group, you naturally stagger your harvest window as you have some early bloomers, some late bloomers, and some in between.
All Lisianthus will initially produce one bud, followed by side branches that make many more buds. I like to remove this first bud when I see it, allowing the plant's carbohydrates to flow to the next series of buds. There are often 3 or 4 of these large buds, and I wait until these are open to harvest. There will likely be a series of buds held just above these open flowers. If they are mature enough they will continue to open in the vase. The tiny buds won't develop after cutting, and some growers trim them off (common in Japan) but most just leave them on.
Lisianthus doesn't need much in the way of post harvest treatment. I cut into a holding solution (such as Chrysal 2), which keeps bacterial levels low and feeds those developing buds. Even in plain clean water, Lisianthus should last well more than a week. 14-21 days of vase life is not uncommon.
In warmer areas where summers are longer you will probably see a second or even third flush of flowers from your Lisianthus. When you harvest, cut them back to a couple pairs of leaves, feed and water them well, and hope for the best. We never get a rebloom in Vermont, but we are also not known for warm summers. In cool climates Lisianthus tends to grow slowly to a very tall and large size.
Fusarium is the biggest disease facing Lisianthus. Unfortunately it is ubiquitous, being found at some level in most natural soils. Fusarium is one of the root rot pathogens that used to be treated with methyl bromide fumigation which, it turns out, is environmentally disastrous. Soil steaming has also been used, but it is a cumbersome process that generally uses significant amounts of petroleum to accomplish, so it is also not often carried out. Your best defense is to help foster biologically diverse and active soil. Bio Fungicide products such as RootShield, Actinovate and PreFence offer some help in battling fusarium as they attach to the roots before they are exposed to the pathogens and provide a protective layer. Even these are not foolproof, but they do offer some level of protection. I have also had good luck using some conventional fungicides labeled for drenching greenhouse crops, and have achieved good preventive control of Fusarium. If you see plants that suddenly wilt or turn brown, suspect fusarium. Rip those plants out immediately, and as a precaution I recommend ripping out the plants growing next to the affected plant to create a firewall of sorts. Put these in your trash, not in your compost, and get rid of them. You can sometimes stop the spread by catching infections early, but sometimes infection has already spread by the time you notice it. As with all fungal issues, managing humidity and air flow will also reduce the spread of fusarium.
When your trays arrive, don't set them on the ground as you unpack them. Place them on a clean bench. The ground is more likely to have fungal spores on it and these can infect your plugs. Wait until after the plugs have been treated to put them in contact with natural soil. (Sterile potting mixes are of no concern).
Word of Wisdom- If you suspect fusarium or see any unexplained disease issue, take a sample and send it to your state plant pathologist. Every state has a land grant university, and should have a plant pathologist on staff, funded by your tax dollars. Testing is usually free or low cost, and will save you the headache of guessing what pathogen you are actually dealing with. Find your state's cooperative extension here.
I say grow what you like the looks of. At the end of the day, they're all the same plant. The difference has more to do with the flower shape and structure than anything else. The big ruffled flowers of series such as Voyage, Celeb, and Corelli tend to hold rainwater more easily than varieties with open centers and smoother petals. I prefer to grow all lisianthus in a tunnel, but for field growing, perhaps avoid the big ruffled types. Of course plenty of folks do well with them outside so I leave this up to you. Trial and error will help you identify the varieties best suited for your conditions.
We offer Lisianthus in 128 and 216 cell trays. 128's are slightly larger and slightly older than 216's, but I see little difference in the end result when either size are planted out at the same time.
Much discussion occurs around the idea of "Bumping Up" Lisianthus on arrival. This is simply the practice of getting your Lisianthus early and then potting them into a larger tray before eventual transplant. There is no right answer. The plugs are ready for more root room when they arrive, be that in the soil, or in a tray. Bumping up has a cost- your time, trays, potting mix and bench space all take up resources. That said if your plugs arrive and you are not ready for them, I recommend bumping up into a 50 or 72 cell tray. On our farm in Vermont we often bump up some trays to give them a head start in our short season. We have also succeeded with direct planting of plugs into soil.
Tips and Tricks
When I was in Japan in 2019, I noticed that growers all leave a bare unplanted strip in the middle of their Lisianthus beds. The middle of beds have the poorest airflow and humidity tends to accumulate more in the middle of a bed. This creates perfect conditions for fungal infection. Keeping this strip open reduces incidence of fusarium troubles. We also leave a 6-12" gap between varieties when planting our Lisianthus beds to provide a physical barrier if and when fusarium strikes. This "moat" of unplanted soils seems to offer a sufficient barrier when trying to manage small outbreaks.
There is no advantage to planting in the fall for growers in the more northerly 80% of the US. If you routinely see freezes and snow, just wait until spring. For growers in Florida and the Gulf Coast to Texas, fall planting will work well. Just remember to plant in the coolest part of your year so the plants can settle in before extreme heat comes back.