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How to plant, grow and care for asters from sowing seed to winter care
Last Updated on May 18, 2020 by John
Asters are perennials known for bringing a lot of colourful flowers at the end of Summer and Autumn when other flowers might be fading. They take on the appearance of a daisy and because there are so many varieties the height of the aster plant can range between 20cm and up to a meter for taller varieties.
That said you can find Asters that attract bees and butterflies and fill any space in your garden.
Asters will grow best in areas with cool, moist summers that have cooler temperatures much like most of the UK. They don’t like the hot summer sun in the middle of the day so it’s important to pick an area in your garden that has between full sun and partial sun. The soil should be well-drained and you can mix some good quality compost into the soil before you plant them in order to amend it.
Sowing seed indoors
If you try to propagate from seed the germination can be somewhat uneven but it’s worth trying. You can still choose to start the seeds indoors about 5-6 weeks before the last frost so for the Uk is usually around April but you can sow them a little earlier. Sow them in seed compost or multi-purpose compost in trays around 0.5cm(1/4in) deep. Keep soil moist and keep in a warm place until they germinate which is usually around 2-3 weeks. Transplant into larger pots, 7-9cm pots are ideal and grow on until they are hardy enough to plant out.
Sowing seeds outdoors
Sow outdoors between April and May in finely prepared soil and plant seeds around 0.5cm(1/4in) deep, keep moist. Once they are germinated you may need to thin out so each plant is 30cm apart.
When to plant out
The best time to plant them is between the middle of spring to the end of spring. Fully grown plants can be purchased from nurseries or garden centres as an alternative to growing from seed.
Allow enough space for the variety you choose and mulch around the base of plants
Be sure to space them between 30cm and 1 metre apart depending on the type and how large they get at maturity. When you plant them, give them lots of water and add mulch around the base of the plant to cool the roots as they are generally shallow rooted and prevent it also helps prevent any weeds from growing.
Caring for Asters
You should add a thin layer of compost with mulch around your plants annually in the springtime to help encourage regular growth and help with moisture retention. Keep plants well-watered as they prefer moist fertile soil but well-drained as they don’t like having wet feet.
Watering regularly especially during dry spells
They are very moisture sensitive so they might not flower as well if they receive too much watering or too little watering. So pay particular attention to the signs of a stressed plant and try to change your watering habits first.
Stake taller varieties to stop them falling over
To prevent them from falling over you can stake the taller plants. To promote bushier shapes you can pinch them back once or twice at the beginning of Summer and this will help them to produce more flowers and help form a bushier plant. In Winter once all the foliage is dead you can cut them back to ground level and add a layer of mulch to help protect the roots.
As with most perennials. It’s important to divide them every three or four years in the springtime to help the plants stay healthy and floriferous.
Pests and Diseases
Asters are very susceptible to some of the more common issues like powdery mildew or leaf spot. These are diseases that usually manifest in the summer when there is inadequate air circulation and warmer temperatures.
Be careful how you water, lookout for signs of mildew and remove any affected leaves and spray with a fungicide.
They are also susceptible to slugs and snails which you can prevent through a variety of measures including eggshells around the perimeter of your plants, beer traps, and copper wire. Aphids are another pest problem that needs to be removed by spraying them off or using a soap solution or using a pesticide spray for more serious infestations.
Last update on 2020-12-01 at 18:12 / Affiliate links / Images from Amazon Product Advertising API