Lisianthus Tips and Tricks for Northern Growers
As many of you know, I wear several hats. We have our farm in Northeastern Vermont, and we also have our plug brokerage business which I accidentally started one winter. (When Mother Nature demands that you take a six-month break from growing flowers you have to get creative). Both on the farm, and in the plug realm, lisianthus is kind of a big deal.
Lisianthus in its wild form is native to a number of the Plains States, extending into the Gulf States and northern Mexico. It occurs in dry sandy locations that get baked in the summer, but it occurs along stream beds where its roots penetrate deep into the soil to access water. When I’m trying to understand what a plant wants I always think about the native conditions first. It can be assumed that heat is no issue for lisianthus, but access to water is important, and cool roots are appreciated.
I’m no lisianthus historian, but I do recall that when I started my floral and horticultural career in the early 90’s, it wasn’t a flower often encountered. It seems that breeders really started getting serious about lisianthus in the 80’s and 90’s, and it took them a couple of decades to refine the plant to the commercial standard we enjoy today. You will still find a high percentage of retail customers who have never seen or noticed lisianthus before. Of course it’s an easy sell for those in the know, and most of what we grow in the U.S. is superior to the imports. The exception is of course the famed Japanese lisianthus. They have a few tricks up their sleeves that I learned when I visited growers in Japan in 2019. We now have access to the same varieties as the top Japanese growers so I hope these tips will help you to fine-tune your lisianthus production.
There are many approaches to lisianthus growing: experiment for yourself and find what works for you in your location. My recommendations are based on my own trials in cool northeastern Vermont, but can be applied to most scenarios.
Tunnels and Plugs
Grow in tunnels. It just works better. The big ruffly flowers hold water and are prone to spotting and rotting when grown in the field. Some grow in the field, but I’ve never had success outside of the tunnel.
Buy plugs. Not because I’m a plug seller, but these things are simply tough to grow from seed. By all means get some seed and see how they go, but order plugs as well until you are confident that you are a lisianthus master. Some people with heated greenhouses succeed with seed growing, as do some with good indoor light systems, but they’re easy to mess up. Frankly I like to travel in winter, and I don’t want to have to stay home to baby seedlings for 3-4 months straight. I prefer the beach.
The Bump Up
For most crops and for most regions of the U.S. I recommend ordering plugs of any sort when you intend to plant them, and planting directly into your prepared beds on arrival. With our short, 90-day growing season I have settled on getting lisianthus early and bumping them into 50-cell trays. It is extra labor, extra potting mix, and it takes up bench space in the greenhouse, but it allows me to baby them for several extra weeks in our cool greenhouse until it’s safe to plant out into our high tunnels. We heat our greenhouse to just above freezing at night, and allow the sun to warm it in the day. Lisianthus copes just fine with the cool nights. I tend to get plugs about 8 weeks before intended transplant, and then grow them in the cool greenhouse until our weather turns and the soil is prepped. If your plugs arrive and you haven’t prepped your beds yet, or your weather prevents planting, bump them up. Don’t hold plugs in their trays for more than a week after arrival.
If you plant directly from the plug tray, which is a completely valid approach in all but the coldest locations, be ready to water. The root portion of a plug is only one inch tall, and the soil on top dries out very quickly. Drip irrigation will only help only once those roots have grown out into your existing soil. Sprinklers, misters, or a good old-fashioned hose will be necessary until they are rooted in.
Fight the Fungus
Lisianthus is susceptible to a wide range of root rot pathogens. Fusarium is the most common, but not the only one. If your soil is well watered but you see sudden spotty wilting, suspect root rot. At first sight of symptoms, yank that plant out and send it to your state plant pathologist to determine what you’re dealing with. It won’t get better on its own, and will likely spread rapidly.
Consider pre-treatment with a biofungicide or two before planting. These products inoculate the roots with beneficial fungi and bacteria to fight off pathogens. Different products have different modes of action, and they can be used together to create a protective barrier around the root zone of your plants. We still see losses to rot even when using biofungicides, so for the first time this year we are trying a pretreatment with a systemic chemical fungicide. I am not qualified to make product recommendations, but if I find something that truly works I might let it slip.
Traditionally, chemical soil fumigation or soil steaming have been used to fight root pathogens. Chemical fumigation has some very negative environmental effects and is no longer fashionable. Soil steaming requires expensive and cumbersome equipment, and burns a significant amount of petroleum to give the desired effect. There is no perfect solution so explore your options. Keep an eye out for root rot, and rotate your lisianthus to a new location every year.
Any crop that is susceptible to any fungus will benefit from good ventilation and consistent air flow. In Japan I saw that growers leave an open strip down the center of each bed to encourage air flow between plants. This may also slow down any possible fungal outbreaks, as the fungi are easily transmitted between neighboring plants and the gap will offer a barrier. We tried this in 2020 with good success and have planted accordingly this season.
Pinch Me—Don’t Pinch Me
I don’t pinch my lisianthus. I prefer to get one monster stem over several medium stems. You may be different. This will depend on your market. If you do pinch, simply remove the tip after you have a few pairs of leaves. I would space pinched plants wider than plants grown for single stems. Pinched plants get bushier, and 6” spacing is justified (4 plants per square foot). For single-stem plants I plant 8 plants per square foot and ultimately harvest 36” tall stems from most varieties. I always use a double layer of support netting, and I’m suspicious of those who don’t.
Bud Trimming, for the Overachiever
It is fairly widely known that cutting out the first flower will allow more buds to open on each stem, resulting in a more marketable stem. You can wait until this flower opens to cut it (some will sell this bloom separately for short design work). In Japan, they remove this bud while still immature to direct the plant’s resources to the next set of buds. Japanese growers also prune their lisianthus to allow only a few blooms to develop per stem, resulting in much larger flowers. When your plants have achieved the desired height, select the 3 or 4 best buds that are all roughly grape sized and at the same height in the plant. Trim off all of the tiny buds growing above this bud, leaving one additional bud above your desired flower as insurance in case your selected flower becomes damaged.
I don’t think anyone else is using this technique in the U.S., but I have noticed that lisianthus tends to grow especially large in northern latitudes, and a bit of additional fussing can result in a product worth a premium price. It’s extra work so you need to charge accordingly. Japanese cut lisianthus sells at high end wholesalers for $5-7 per stem, so if you can achieve this quality you should be able to get an enviable price.
Many report getting a second and third flush of flowers from lisianthus, but in the cool north this seems like pure mythology. I get one amazing stem per plant, and then it’s winter.
Again, these ideas are simply what work for us. Have your own tips and tricks? Send them my way!
Wishing you a fungus-free lisianthus season!