Stokesia

( stoh - KEE - see - uh )

At-A-Glance Information

Commonly called Stoke's Aster, this perennial flower grows well in full sun and needs regular water. It is a vigorous plant and is native to the southeastern United States. Plants are evergreen in mild climates and semi-evergreen elsewhere. Foliage is green and flowers blossom in summer or early autumn. Blooms can be purple-blue, blue or white, and make great long-lasting additions to cut flower arrangements. They are wonderful in pots, and grow best in zones 2-10 and 14-24 (to find your zone, click here: Zone Map). The genus Stokesia includes just one species, Stokesia laevis, and varieties include 'Blue Danube' (blooms into wintertime in mild climates), 'Silver Moon' (with white blooms), 'Purple Parasols' (with deep purple flowers) and 'Klaus Jelitto' (with powder-blue blossoms). It is a member of the plant family Asteraceae.

Caring for Stokesia

Stoke's Aster can be purchased as seed or as specimens from a reputable nursery. They are typically spaced between 20 and 24 inches apart for best coverage, though this varies somewhat depending on the cultivar grown. Pick a space in the landscape that receives full sun; ideally, these flowers appreciate between 6 and 8 hours of direct sun each day, with some late afternoon shade when temperatures are at their warmest. If you are in an area where winter temperatures are low, make sure to plant Stoke's Asters in a sheltered spot. Ensure that soil is well-draining, moderately rich in nutrients, and has a pH of between 5.5 and 7.5 (acidic to neutral). If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Apply a layer of mulch around the planting area to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water new plantings regularly as they establish a strong root system in their new home. At maturity, Stoke's Aster plants are considered to be relatively drought-tolerant, able to get by on rainwater alone for most of the year with supplemental irrigations during periods of drought.

Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. These plants are not heavy feeders, and this should be sufficient to provide the necessary nutrients for the active growing and flowering seasons. Pruning is simple; remove any damaged, diseased, or dead foliage at any time during the growing season, and remove spent flower spikes to neaten up the appearance of plants, encourage reblooms, and to extend the flowering season farther into summertime. Every few years, when these plants decline in performance, they will need to be divided. For instructions on how to successfully divide Stokesia plants, see the propagation section below. Stoke's Aster plants typically last for around 5 years in the garden before needing to be replaced.

Growing Stokesia in Containers
Stokesia can be grown either in the ground or in containers. In areas with cool winter temperatures, growing in pots allows for bringing these plants into a more sheltered location over the winter. Start with a container that has great drainage holes on the bottom (or drill additional holes to make it so). Fill the container with well-draining soil amended with plenty of organic material or compost. Apply a layer of mulch over the top of the planting to suppress weed growth, maintain consistent soil temperatures, and increase soil moisture retention. Stoke's Asters that are grown in containers will need more frequent irrigation than those in the ground, however they are still considered to be drought tolerant, and soil can be allowed to fully dry out between waterings. When Stoke's Asters outgrow their container, they can be divided and replanted. For instructions on how to successfully divide Stokesia plants, see the propagation section below.

Harvesting Stokesia Cut Flowers
With their 3-4 inch wide blooms, Stokesia flowers are a knockout in cut flower arrangements and bouquets. Taller varieties of Stoke's Aster are perfect for cut flower gardens, and do not typically need support or netting to remain upright during the growing season. These flowers should be harvested when they have fully opened, their stems cut back to the base of the plant using sharp, clean shears or snips. Immediately after harvesting, drop stems into a cool bucket of water. Stoke's Aster typically lasts about a week in a vase.

Propagation

Stokesia, or Stokes' Aster, can be propagated by division, cutting or seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the division or cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant, especially if you are propagating a hybrid cultivar. To propagate your Stokes' Aster, follow the instructions below:

Propagating Stokesia by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
Harvest your seeds. The seed heads on plants are pretty easy to spot, they're left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will continue to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
Get your container prepared. Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 2-6 weeks from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 65 and 72 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.

Propagating Stokesia by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
In early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 3-4 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new plant.

Propagating Stokesia by Division
This type of propagation is relatively simple; you will need a clean shovel, mulch, fresh soil (any kind will do, though it does need to be well-draining), compost and pots (only necessary if you will be saving divided plants for transporting elsewhere). Division is best done in very early spring (after the plant has entered dormancy, but before it has begun its new spring growth), and needs to be done every few years regardless of whether you have the goal of propagating the plants for best performance. To propagate by division, follow these steps:

Using a shovel, dig up your existing plant. Start from the outside and work your way in to avoid damaging the root(s). Once you have worked it up out of the ground, lay it out.
Start to tease apart the roots with your gloved fingers. Once the roots are untangled, separate your plant into segments, ensuring that each one has at least one thick root section attached.
Prepare your pot(s) or new planting site(s) with amended, well-draining soil. You can either bring in new soil or simply amend your existing soil with compost to complete this task. Then, plant your divisions and water thoroughly.
Apply a thick layer of mulch over the new planting to protect it from cold weather as it acclimates to its new home. Then, enjoy watching it sprout in the next growing season.