Lisianthus Growing Secrets for Bigger, Premium-Quality Blooms

As many of you know, I have several different roles. We operate our farm in northeastern Vermont, and I also run a plug brokerage business that I started somewhat accidentally during one winter. When Mother Nature forces you to take half the year away from growing flowers, you have to find other ways to stay busy. In both our farm operation and our plug business, Lisianthus has become an especially important crop.

In its natural habitat, Lisianthus is native to several states across the Great Plains, extending south into the Gulf states and northern Mexico. It can be found in dry, sandy areas that become extremely hot during summer, but it also grows along streambeds where its roots can travel deeply into the soil in search of water. Whenever I want to understand what conditions a plant prefers, I start by considering where it naturally grows. From that perspective, it is clear that heat itself is not a major concern for Lisianthus. Reliable access to moisture is important, however, and the plants benefit from having cool root systems.

I am certainly not a Lisianthus historian, but I remember that when I entered the floral and horticultural industry in the early 1990s, Lisianthus was not a flower I encountered very often. Breeders appear to have devoted considerable attention to the crop during the 1980s and 1990s, and it took several decades of improvement to develop the plants into the commercial-quality flowers we know today.

Even now, many retail customers in the United States have never noticed or encountered Lisianthus before. For people who are familiar with it, however, it is generally an easy flower to sell, and much of the Lisianthus grown domestically is better than imported material. One notable exception is the highly regarded Japanese Lisianthus. Japanese growers have developed several techniques that I learned about during a visit to growers in Japan in 2019. We now have access to many of the same varieties used by leading Japanese growers, so these suggestions may help you refine your own Lisianthus production.

There are many different ways to grow Lisianthus, so it is worth experimenting and determining which methods perform best under your own conditions. My recommendations come from trials conducted in cool northeastern Vermont, although many of these practices can be adapted to other growing situations.

Grow in Tunnels

Growing Lisianthus in tunnels simply produces better results for us. The large, heavily ruffled flowers retain moisture, which makes them particularly vulnerable to spotting and rot when grown outdoors in the field. Some growers successfully produce Lisianthus in field conditions, but I have never achieved comparable results outside of a tunnel.

Buy Plugs

This recommendation is not simply because I sell plugs. Lisianthus is genuinely difficult to raise successfully from seed. You should certainly experiment with seed if you want to learn how it performs, but it is wise to order plugs as well until you become confident with the crop.

Some growers with heated greenhouses can successfully raise Lisianthus from seed, and others achieve good results using effective indoor lighting systems. However, seedlings are easy to mishandle. Personally, I enjoy traveling during the winter and would rather not spend three or four continuous months at home caring for young seedlings. I would much rather be at the beach.

The Bump Up

For most crops and in most parts of the United States, I recommend receiving plugs close to the time you plan to plant them and putting them directly into prepared beds as soon as they arrive. Our growing season is only about 90 days, though, so I have settled on receiving Lisianthus plugs early and moving them into 50-cell trays.

This method requires additional labor, extra potting mix, and valuable greenhouse bench space. However, it gives me the opportunity to carefully grow the young plants for several additional weeks inside our cool greenhouse before conditions are suitable for transplanting them into the high tunnels.

We keep the greenhouse temperature just above freezing at night and allow sunlight to raise the temperature during the daytime. Lisianthus handles these cool nighttime conditions quite well. I generally receive plugs about eight weeks before the planned transplant date and keep them growing in the cool greenhouse until outdoor conditions improve and the beds have been prepared.

If your plugs arrive before your beds are ready, or unfavorable weather prevents you from planting them, move the plants into larger containers. Do not leave the plugs sitting in their original trays for more than a week after they arrive.

Planting directly from the plug tray is also a perfectly reasonable method in most areas other than the coldest climates. If you choose this approach, however, be prepared to provide plenty of water. The root section of a plug is only about 1 inch tall, and the upper inch of soil can dry out extremely quickly.

Drip irrigation will not become particularly useful until the roots have expanded into the surrounding soil. Until that happens, sprinklers, misters, or even a traditional garden hose may be needed to keep the young plants adequately hydrated.

Fight the Fungus

Lisianthus can be affected by a broad range of pathogens that cause root rot. Fusarium is the most frequently encountered problem, but it is certainly not the only pathogen capable of causing damage. If your soil has adequate moisture but individual plants suddenly begin wilting in scattered areas, root rot should be considered a possible cause.

As soon as symptoms appear, remove the affected plant and have it examined by your state plant pathologist so you can determine exactly what pathogen you are dealing with. Root rot will not normally resolve by itself and can spread quickly through a planting.

You may also want to consider treating the plants before planting with one or more biological fungicides. These products introduce beneficial fungi and bacteria around the roots, helping compete with harmful pathogens. Different biological products work through different mechanisms, and some can be combined to create a protective zone around the plants' root systems.

Even with biological fungicide treatments, we continue to experience some losses from root rot. For the first time this year, we are therefore experimenting with a pretreatment using a systemic chemical fungicide. I am not qualified to recommend specific products, but if I discover something that provides genuinely effective results, I may eventually share what I learn.

Chemical soil fumigation and soil steaming have traditionally been used to manage soilborne root pathogens. Chemical fumigation can have serious environmental consequences and is no longer considered a particularly desirable option. Soil steaming, meanwhile, requires costly and cumbersome machinery and consumes a considerable amount of petroleum to produce the necessary heat.

There is no single perfect answer for controlling these pathogens, so investigate the options available in your situation. Monitor plants carefully for signs of root rot, and consider moving your Lisianthus crop to a different growing area each year.

Air Flow

Any crop that is vulnerable to fungal diseases can benefit from strong ventilation and steady air movement. During my visit to Japan, I noticed that growers left an open strip running down the center of each bed. This design encourages air circulation between the plants and may also help slow the spread of fungal diseases.

Fungal pathogens can move easily from one neighboring plant to another, while the open space between rows can provide an additional barrier. We tested this approach in 2020 and were pleased with the results, so we have continued using the same planting arrangement.

Pinch Me, Don’t Pinch Me

I personally do not pinch my Lisianthus plants. I prefer producing one exceptionally large stem rather than several stems of moderate size. Your preferred method may be different, depending on the needs of your market.

If you decide to pinch the plants, remove the growing tip after the plant has developed several pairs of leaves. Pinched plants should generally be given more room because they become bushier as they develop. A spacing of 6 inches is reasonable, which works out to approximately four plants per square foot.

For single-stem production, I plant eight plants per square foot and eventually harvest stems measuring about 36 inches tall from most varieties. I always install two layers of support netting, and I remain skeptical of anyone who claims they can grow Lisianthus successfully without it.

Bud Trimming for the Overachiever

It is fairly well established that removing the first flower can encourage additional buds on each stem to open, producing a stem that is more valuable for the cut-flower market. You can wait until the first flower has opened before cutting it. Some growers may even sell that individual bloom for shorter floral designs.

Japanese growers take this technique one step further by removing the first bud while it is still immature. Doing so redirects the plant's energy toward the following group of buds. Japanese producers also selectively remove buds so that only a small number of flowers develop on each stem, allowing the remaining flowers to become considerably larger.

Once the plants have reached your desired height, choose three or four of the strongest buds. Ideally, they should all be approximately grape-sized and positioned at a similar height on the plant. Remove the smaller buds developing above your selected flowers, but leave one additional bud above the flowers you intend to keep as insurance in case one of your chosen buds becomes damaged.

I do not believe this particular technique is widely practiced elsewhere in the United States, but I have noticed that Lisianthus often grows exceptionally well in northern latitudes. Giving the plants a little additional attention can therefore produce flowers with enough quality to justify a premium price.