How to Grow Lisianthus: The Complete Guide

Lisianthus likes full sun, about 6 to 8 hours daily, but afternoon shade is beneficial in regions with sweltering summers. Good drainage is necessary. Soil rich in organic matter is ideal, and a pH of 6.5 to 7.0 is the sweet spot. Amend beds with leaf litter, compost, and aged manure. 

If your flower patch is short on room, don’t despair; these flowers grow well in containers on the deck or patio.

When to Plant Lisianthus 

In most locations, you can transplant lisianthus into outdoor beds about 4 weeks before your last frost date. 

If you are growing from seed, you can count backward from your transplant date—a long way back. Lisianthus can take 3 to 5 months to be ready to plant out. For most of us, start about 4 months before your transplant date.

Lisianthus likes cool weather to become established when transplanted and can take some moderate frost even as seedlings. Light frosts won’t hurt it, but if you get a cold snap, about 20F or colder, you’ll want to cover them with frost cloth for the night unless covered in snow.

How to Start Lisianthus From Seed

Lisianthus seeds are tiny, so buying pelleted seeds can make them much easier to handle. Soil blocks work well, but lisianthus can also be planted in small cell trays. 

• Pre-moisten your seed starting mix, then sow one seed per block or cell.
• Lisianthus seeds need light to germinate, so press them lightly to ensure good seed-to-soil contact and then apply a thin layer of vermiculite. 
• Keep the seed starting mix evenly moist (but not drippy wet) until germination, which can take two weeks. A humidity dome or plastic covering will help keep the moisture in.
• After they sprout, remove the humidity dome and let the medium slightly dry out between waterings. Don’t let them get too dry and wilt. With many potting mixes, the soil will change color a bit when dry, but I like to feel them to be certain. If they’re dry to the touch or very lightweight, it’s past time to water. 
• Fertilize weekly with a dilute solution. The small seedlings will be in their trays or soil blocks for months. Eventually, they will use up the available nutrients and stop growing without supplemental fertilizer.
• Don’t let the trays get too warm. If temps get high for a while, above 75-80℉, baby lisianthus may start to rosette and put out a bunch of growth from the base. Those that do this will likely never flower. 
  Lisianthus will still be small when transplanted–probably only an inch tall. Ideally, they should have four sets of leaves. 
• When transplanting, space the seedlings 4 to 5 inches apart and stake or net them when you plant. 
• They’ll need support by staking or using netting, and it’s easier to do it right away than to forget and try to weave stems through the netting later. Their heads get heavy with the huge blooms, and they will likely flop.