Asters Guide: How to Grow & Care for “Symphyotrichum”

Our Guide to Asters Flowers for everything you will ever need to know! Tips for planting & caring for “Symphyotrichum”

All gardeners secretly love having their flowering plants around for as long as possible. Sadly, our beloved plants tend to hide their flowers once the summer months are no longer around, leaving us all shattered. No worries, we have the solution! Keep reading to find out more about this interesting fall-blooming species and how you can grow and care for them.

Symphyotrichum (formerly Aster) is a genus that contains more than 90 species of gorgeous flowering plants in the Asteraceae family. Most flowers from this genus are endemic to North America. However, some of them can also grow in several regions of eastern Eurasia, Central and South America, or West Indies.

With time, many Aster species occurred worldwide as ornamental buddies in both outdoor and indoor settings. The most popular cultivars are S. novae-angliae (New England Aster) and S. novi-belgii (New York Aster). These beauties make for excellent additions to cottage gardens, butterfly gardens, or late summer and fall borders. They also look absolutely adorable in pots and can add a nice dash of colour indoors as cut flowers.

About Asters

  • Their name derives from the word “aster”, which is the Greek for “star”. This name refers to the shape of Aster flower heads, which look very much alike with a star.
  • Thanks to their stunning overall appearance, the cultivars Aster alpinus and Aster amellus have gained the prestigious Award of Garden Merit.
  • Their flowers are highly attractive to several species of pollinators like flies, bees, and butterflies. They also serve as a delicious food source for the larvae of some Lepidoptera species.
  • Aster plants played a big part in traditional Chinese medicine. Many folks used them as a treatment for venereal diseases, headaches, or digestive problems.
  • In the past, the roots of these plants worked as a healthy ingredient in different soup recipes. People also cooked young leaves lightly and consumed them as greens.
  • Although eating Asters is no longer a popular practice, they still have their place among natives. They use these plants as garnish and make for great additions to tea blends or fresh salads.
  • The perfect time to plant young specimens of Asters is from mid to late spring. When it comes to mature and potted plants, autumn is the suggested season for planting.
  • Many species of Asters are tolerant of drought for short periods. They can thrive only with a little touch of water for one week but prefer constantly damp mediums.
  • While ingesting or touching some Asters have no toxic effects on cats and dogs, others may cause a few digestive problems or irritation. For safety purposes, grow these plants in a spot where your curious pets cannot reach them.

Asters Features: An Overview

  • Asters are herbaceous perennial or annual plants that can reach from 1 to 6 feet (0.3-1.8 m) in height and 1 to 4 feet (0.3-1.2 m) in width, depending on the cultivar.
  • Their foliage consists of simple, thin, pointed, and dark green leaves that grow alternately arranged on long, slightly woody stems. The leaves can appear as toothed or untoothed, but rarely lobed.
  • In general, these plants bloom from early summer to late fall. During this period, they produce an abundance of small, daisy-like, and star-shaped blossoms with disc florets and ray florets (petals).
  • The disc florets are usually white to yellow and become reddish, pink, purple, or brown when mature. Their petals come in various shades of white, pink, purple, and blue.
  • The seeds of Aster plants are tiny achenes and look similar to parachutes. They spread very easily by wind and can also be a viable propagation material.
  • Asters can be great ornamental companions to other mesmerizing species of plants including Black-Eyed Susan, Dahlia ‘Chat Noir’, Fountain and Purple Fountain Grass, Mountain Fleece, and Sedum ‘Autumn Joy’.

Growing Asters

Asters are one of those easy-going flowers that can thrive with as much light as you can give them. Whether you want these plants outdoors or indoors, grow them in a location where they can receive full sunlight for the majority of the day. Still, some native species varieties will do just fine if you plant them in a spot with partial shade exposure.

When it comes to temperatures, you will have no major issue with these flowers. Aster plants are somehow frost hardy, being able to tolerate near-freezing temperatures for short periods. They thrive in slightly warm to mid-cool temperatures but also require some protection during the harsh winter months. In regions with freezing conditions, it is better to grow your babies in pots and bring them inside until spring.

Aster Mix Seeds – Approximately 2500 Seeds, From Amazon

Although Asters are not so attractive to most pests, lace bugs can bother them from time to time. The most common symptoms of infestations include yellow foliage and leaf drop, usually in the summer. If you notice any of these signs, coat all sides of the foliage using insect soap to get rid of the intruders as soon as possible.

Some diseases like powdery mildew and rust can also damage Aster leaves and stems. Before planting, make sure you provide enough space between your plants to improve air circulation. Moreover, this process will help you avoid splashing the water on their foliage and over-watering.

Planting Asters

In terms of growing medium, you can plant your Asters in any loamy and slightly acidic soil with a pH range of 5.8 to 6.5. If your substrate is alkaline, you can improve its quality by adding some organic matter in it, such as compost, leafmould, or well-rotted manure. To avoid soggy conditions in the watering routine, make sure you plant your flowers in well-draining soil.

In general, Aster plants are moderate feeders that will benefit from regular fertilizing from spring until their flowers begin to open. For profuse blooming, feed your plants with a balanced flower fertilizer twice a month. You will want to stop fertilizing them in August, as too many nutrients can shorten their flowering period.

Some cultivars like Bushy Asters have a shrub-like overall growth and may require pruning once in a while. If you want to maintain a certain size or shape for your plants, you must trim off old, damaged, or dead parts of their foliage in spring. You can also remove all the spent flowers during their blooming time to ensure new ones occur in their place.

Watering Asters

Having no high demands regarding their watering routine, Asters are ideal companions especially for growers that do not have so much experience in the gardening world. In general, these plants can do well with only one inch (2.5 cm) of rain or irrigation weekly. However, they will need some extra attention from you until they settle in their new environment.

Provide new Aster planting with water as often as needed to maintain their soil constantly damp. You should repeat this process regularly until their blooming season ends, usually in late fall. Once this period has passed, you can start to use their permanent watering routine.

Pink Asters
Pink Asters

For both indoor and outdoor settings, make sure you always check the soil in-between waterings. When the top inch (2.5 cm) of soil feels dry to the touch, your plants will be ready for another drink. As a general rule, it is better to water the base of your plants without splashing it on their leaves to avoid fungal diseases.

Propagating Asters

Aster plants are a must-have in any garden or home only for their magnetic presence alone. Believe us, they will charm your beloved family members and friends in less than a moment! Luckily, you can propagate these flowers through various methods including division, sowing seeds, and rooting stem cuttings.

As always, we are here to make your gardening journey as enjoyable as possible. Due to this, we warmly recommend you to propagate Asters by division for guaranteed results and faster growth. This method is way easier than the other two and, most importantly, very beginner-friendly!

First things first, you must dig out the root clumps of your Asters and remove any excess soil. Their roots are pretty tough, so you should use a sharp spade to divide the clumps into pieces. Once you have the tiny roots, you can plant them anywhere you want as long as you provide enough space between them.

After replanting, make sure you provide the Aster clumps with a nice and deep soaking. Moreover, they will benefit from a nice phosphorus boost, such as bone meal, to show results faster. The baby Asters will survive no matter when you perform the propagation, but early spring or late fall clumps will put flowers on display only in the next year’s autumn.

In Conclusion

Now that you know how simple it is to grow, care for, and even propagate Asters, how could you possibly resist them? As long as you pay attention to their minimal requirements, you will have these cuties by your side for a very long time. So, what are you waiting for? Go on and give them a try!

Are you growing Asters? Share your experience in the comments below!

Miruna is an experienced content writer with a passion for gardening. She is the proud owner of an outdoor rose garden and an indoor collection of tiny succulents. She bought her first succulent 10 years ago - an adorable Echeveria Setosa. Now she owns more than 100 succulents and cacti of different colors, shapes, and sizes. Miruna is a versatile writer and, as you might have guessed, her favorite topic is gardening. Contact

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