Liatris is usually planted from potted nursery starts or corms in the spring after the last frost date. Either way, they usually flower in their first year. Starting from seeds is also possible, though it can take two years for plants to flower. Liatris takes very little care, but you may need to stake up the stems if planted in overly-rich soil, which can cause the plant to grow tall and floppy. Liatris can also be grown from seed, although patience is required: The first blooms take two years or more to appear.
Light
Choose a site with full sun to plant your liatris corms. These are prairie plants in their native habitat, so the more sun, the better they will perform.
Soil
Just about any soil, at any level of fertility, will successfully grow Liatris corms, although quick drainage is essential to prevent rot. Very rich soils may require that you stake the plants, as the stalks can be a bit floppy. Liatris plants prefer a slightly acidic to neutral soil pH. Heavy clay can cause root rot, especially in winter, if the soil doesn’t drain well.
Water
After planting, water the corms thoroughly. The corms need no additional irrigation until stalks sprout. As the plants begin active growth, 1 inch of water a week during the hottest months will prevent stunted flowers and leaf scorch. Apply water to the base of the plants, or use drip irrigation, to avoid spreading fungal diseases. These plants need more water in their first year; afterward, they have very good tolerance to drought and dry soil conditions.
Temperature and Humidity
Hardy in zones 3 to 9, Liatris is quite tolerant of summer heat and humidity in warm climates, and will nicely survive very cold winters provided that soil is not too wet. Wet winter soils can cause the corms to rot.
Fertilizer
Liatris is not a heavy feeder, but if the soil fertility is poor you can apply a balanced flower fertilizer each spring as active growth begins. In most decent soils, however, Liatris usually does fine with no feeding whatsoever.
Types of Liatris
Liatris spicata, the most common garden species, is very often planted in its original native form. There are also several named cultivars that are popular:
‘Alba’ has pure white flowers and grows about 18 inches tall.‘Callilepsis’ has the expected purple flowers on especially long stems that are ideal for cut flower arrangements.‘Kobold’ is a smaller, more compact variety with deep-purple flower heads. This variety is a good choice for the foreground of mixed perennial beds.‘Floristan White’ has 3-foot flower spikes blooming in July. It is known for having an especially long bloom period.‘September Glory’ blooms from August to September with 4-foot purple spikes.
There are also two other Liatris species that you may want to know about:
L. aspera (rough blazing star) has purple flowers that grow from 15 to 40 inches tall, depending on location. It has less showy flowers but is a good performer for dry, barren soil.L. pycostachya (prairie blazing star or Kansas gayfeather) blooms later, in August through September. It is available in white, purple, or rose-purple flowers, on spires that are 2 to 5 feet tall.
Propagating Liatris
As a Liatris plant matures, it typically develops offset corms. Liatris is quite easy to propagate by digging up the root corms and separating them. Doing this every few years will also help rejuvenate the plants and extend the life of a clump. Here’s how: Other Liatris species tend to grow from rhizomatous roots rather than corm structures. With these, propagation is a matter is cutting the rhizomes into large sections for replanting.
How to Grow Liatris From Seed
Liatris is not hard to start from seed, either from purchased commercial seed or from the tiny seeds you collect from the dried flower heads in late fall. (Note: if you collect seeds from a hybrid cultivar, the plants will not come true to the parent.) But be aware the seeds will require 4 to 6 weeks of cold stratification in order to germinate. This can be achieved if you direct sow the seeds in the garden in the fall, or if you store the seeds in the refrigerator before planting them in indoor starter trays six to eight weeks before the last spring frost. If starting indoors, plant the seeds in small pots or starter trays filled with standard potting mix. Moisten the mix, then plant the seeds in groups of three to five seeds, just barely covering them with additional potting mix. Place the containers in a spot that receives morning sun and where nighttime temps remain above 50 degrees Fahrenheit. Keep the potting mix moist until the seeds sprout, which usually takes two to four weeks. Keep the seedlings moist as they grow in a sunny location until it’s time to transplant them outdoors after all danger of frost has passed. Harden off seedlings before planting them in the garden. New seedlings may need protection from feeding rabbits for the first year. When planted from seeds, Liatris usually does not bloom until the second year.
Potting and Repotting Liatris
Native perennials such as Liatris are not commonly grown in containers, but it is certainly possible to do so. Any well-draining container filled with a good porous potting mix will work for growing Liatris. Planting and care are identical for in-ground plants, but you will probably need to water more often, as the soil in containers tends to dry out faster than garden soil. To ensure winter survival, move the containers to a sheltered location as freezing weather sets in. Some gardeners have success placing containers in a cold frame or cool garage, heaping them with mulch, or even burying the container in the garden for winter. But don’t try to bring a potted Liatris indoors to grow as a houseplant over winter, as these plants require weeks of cold dormancy in order to reset themselves for spring growth.
Overwintering
Within its hardiness range, Liatris needs no special winter cold protection. The normal routine is simply to cut off the flower stalks near ground level, though you can also leave the flower heads in place for the benefit of winter feeding birds. Liatris does not like wet winter soil, so it’s best to avoid heaping mulch over the plant crowns for the winter, as this can trap moisture and encourage bulb rot. And make sure to clean away soggy garden debris in the spring before new growth begins.
Common Plant Diseases
Liatris does not suffer from any serious insect problems, but several fungal diseases can occur, including leaf spot, rust, stem rot, powdery mildew, and verticillium wilt. The best approach is to prevent these diseases by giving the plants good sunlight and air circulation. Mild fungal diseases, such as leaf spot and powdery mildew, are usually not serious and may not even require treatment. More severe diseases sometimes can be treated with fungicides but may be necessary to remove and destroy badly affected plants.
How to Get Liatris to Bloom
Liatris is one of the longer-blooming perennial flowers, generally providing a display from July into late fall. This is because the flower spikes are really dense clusters of tiny star-shaped flowers, which open in succession, beginning at the top of the spike. This ample flowering habit is routine for mature plants that are getting plenty of sun, but young plants sometimes withhold flowers for the first year or two until the root systems become well established. If you are patient, you are usually rewarded by mature plants that flower profusely. If mature plants fail to bloom at all, it may be a problem of soil fertility; try blending in a slow-release fertilizer into the soil around the plants each spring. Also, check to ensure the plant receives enough sunlight.
Common Problems With Liatris
As a hardy native wildflower, Liatris generally thrives with relative neglect. When problems occur, it is often the result of too much care—too much soil fertility or too much watering.
Flower Stalks Flop Over
Liatris is a plant that is quite sturdy when growing in average or poor soils, even rocky, gravelly soil. In most cases, staking the plants is not necessary. But paradoxically, very rich, fertile soils can cause the flower stalks to topple over. In this case, you may need to stake up the flower stalks; and you can probably safely reduce or eliminate your feeding routine.
Plants Turn Mushy, Break Off at Ground Level
This is the classic symptom of stem or corm rot, caused by wet soil that introduces fungal disease into the roots or stems. These plants will need to be removed. Future problems can often be avoided by reducing water or improving the drainage of the soil.
You can assist this process by digging up the entire clump every few years to divide the corms and replant them to maintain a vigorous colony. Crafters will appreciate adding dried Liatris to their wreaths and garlands: Harvest the flowers at the peak of blooming, strip away the stems and leaves, and hang the flowers upside down in a dry room.
