Knowing when to plant liatris bulbs can mean the difference between a strong bloom and a weak no-show year. Plant your corms in spring once the worst frost has passed and the soil starts to warm. The right liatris planting time is March to April in warm zones and April to May in cold zones.
One quick note before we go further into the timing. Liatris does not really grow from true bulbs at all. The plant grows from corms, which look like flat round bulbs but work in a slightly different way under the soil.
Most folks still call them bulbs at the garden center, so the name sticks around. Either way, the care and planting timing stay the same for you. Just know that what you are planting is a corm, not a true bulb like a tulip or daffodil.
I plant my corms in early April here in zone 5 each year without fail. The soil has thawed by then but still feels cool to the touch. Last year I tucked twelve corms in on April 5th and saw the first green tips push up about 4 weeks later.
Why does the timing matter so much for these plants? The soil needs to warm enough to wake the corm from its winter sleep. Plant too early and the corm can rot in cold wet soil before it sends up any shoots.
Plant too late and you miss the spring growth window when roots get going. The corm needs time to push roots down before the heat of summer hits. Spring liatris planting works best when the soil reads about 50°F (10°C) at planting depth.
Longfield Gardens calls for a March to May planting window across most of the country. Other top sources agree that spring is the right liatris corm planting month for almost all zones. I have not found any expert that calls for summer or hard winter planting.
For zones 7 to 9 in the south, plant in March or early April when the soil first warms up. Some southern gardeners can also plant in late fall around October. The mild winter will not harm the corms in those warm zones.
For zones 3 to 6 in the north and midwest, wait until April or May for safe planting. Check that the soil is no longer frozen and that hard frost is past. I use the rule of thumb that I plant the week after my last frost date each year.
Skip fall planting in zones 3 to 6 since the corms will not have time to root before deep cold hits. I tried this one year in October and lost six of eight corms by spring. Stick to spring planting in cold zones and you will get strong growth each year.
Plant your corms about 4 inches deep with the pointed tip facing up and the flat side down. Space them 12 to 15 inches apart for the best look and growth room. Water once at planting and then let nature take over from there.
Mark the spot with a small stake or label so you do not dig up the corms by mistake later. Corms can sit dormant for weeks before sending up shoots, and you might forget where they are. A simple label saves you the heartache of slicing a corm in half with your trowel.
Read the full article: Liatris Plant: Complete Growing Guide
