How to Care for Your New York Asters Like a Pro

Selecting native plants helps attract beneficial pollinators and other wildlife, conserve water, and prevent erosion.

The New York aster is a low-maintenance North American native that adds a splash of daisy-like color to your fall landscape. 

This deer-resistant flower, formerly part of the Aster genus before it was reclassified as part of the new Symphyotrichum genus, is perfect for rock and cottage gardens.

Its salt tolerance also makes it a popular addition to coastal landscapes. All these clump-forming plants need is a sunny spot with well-draining soil to thrive.

New York Asters Care

Here are the main care requirements for growing low-maintenance New York asters:

• Position in a full sun. Partial shade is acceptable if it’s the only option.
• Plant in a well-draining, fertile soil.
• Amend soil with compost or feed high-phosphorus fertilizer in the spring.
• Divide every couple of years to retain vigor and prevent air circulation issues.

Light

To get the best blooming performance from your New York asters, select a full sun position where they receive at least six to eight hours of sunlight. They can handle part shade, but they won’t produce as many impressive flowerheads. 

Soil

One of the attractions of New York asters is their adaptability to a wide range of soil conditions, although they do like one that is well-draining.

They can grow in sandy, loamy, and even nutritionally poor clay soils. However, to help them thrive, they do best in fertile, loamy, soil rich in organic matter. This helps promote prolific blooming and taller stems.

Water

New York asters can tolerate some neglect and are relatively drought-tolerant. However, the foliage and flowers suffer if they are left dry too long. Keeping the soil evenly moist but not soggy promotes the healthiest growth.

Temperature and Humidity

New York asters prefer temperate climates where they won’t be exposed to extreme hot or cold weather. Fortunately, if you experience an unexpected heat wave, these plants might wilt but should recover when temperatures cool again. 

These plants thrive in average humidity levels. While higher humidity isn’t a major problem if your New York asters are appropriately spaced, it can increase the chances of fungal diseases occurring if the clumps are overcrowded.

Fertilizer

Native plants don’t typically need fertilizer to survive, but providing extra nutrients for your New York aster can promote prolific blooming and vigorous growth.

At the start of the spring growing season, amend the soil with compost or feed with a water-soluble fertilizer.

Pick a fertilizer formula high in phosphorus to focus on root and flower rather than foliage growth.

Types of New York Asters

New York asters are popular plants with many cultivars to choose from. Some popular varieties include:

• Symphyotrichum novi-belgii ‘Coombe Violet’: The deep violet, semi-double flowers on this cultivar stand out from the crowd. This tall cultivar can reach up to 4 feet tall, so it might need staking.
• Symphyotrichum novi-belgii ‘Fellowship’: Featuring pretty pale pink double flowers. Another tall cultivar, be ready to provide the stems with some support to stop sagging.
• Symphyotrichum novi-belgii ‘Ruby Red’: The striking mulberry red semi-double flowers are more compact. Reaching up to 2 feet tall, they are ideal eye-catching additions for cottage garden borders.

Pruning

New York asters are flowers you can plant and leave, but a little extra attention tidies their appearance, promotes bountiful blooms, and increases their longevity.

Pruning the stems in late spring to around half the original height or 6 inches tall can help produce a bushier, more compact habit and strong stems that are less likely to flop when unstaked. 

Deadheading or cutting back immediately after blooms fade helps prevent the self-seeding of these aggressive spreaders. 

Propagating New York Asters

You can easily add more New York asters to your collection by propagation. You can do this through cuttings or from seed. However, because division is recommended every two to three years to promote good air circulation and healthy growth, this is the most popular propagation method. 

Follow these steps in the spring to propagate your New York asters by division.

1. It’s best to wait until your New York aster plant is three years old and has a robust root system.
2. Divide the clump into two parts with a sharp shovel.
3. Replant the sections, providing the same type of conditions.
4. Amend the soil with compost or bone meal.
5. Keep the soil evenly moist until the divisions are well established.

How to Get New York Asters to Bloom

Learn more about the daisy-like blooms of New York asters to make the most of them. 

Bloom Months

Long-blooming New York asters are the perfect flowers for adding color in fall. They typically bloom at some point from late summer (the end of August) to the first fall frosts.

The reason one of their common names is Michaelmas daisies is because they are often in bloom on St. Michael’s Day; which is the 29th of September.

What Do New York Aster Flowers Look Like?

The flowers of the New York aster are daisy-like. The flower head forms are commonly semi-double or double and are around 1 inch in diameter.

Petal colors can be shades of purple, violet, pink, or white and typically have yellow disk centers. The blooms tend to droop and close at night, but they bounce back after sunrise.

How to Encourage More Blooms

Young plants don’t typically bloom for the first year or two while establishing a robust root system.

Ensure any fertilizer you feed is higher in phosphorus than nitrogen to direct energy to flowers rather than foliage.

And divide clumps every two to three years to promote healthy, disease-free blooms and better air circulation.

Common Plant Diseases

The biggest problems for New York asters are often created because of poor air circulation. As these clump-forming plants begin to get overcrowded, they can suffer from the fungal disease powdery mildew, particularly in the summer months. 

Thinning out clumps by dividing every two to three years, positioning in a sunny spot, and carefully irrigating at the plant base can all help prevent powdery mildew.

If you catch it early enough, it's not too difficult to treat powdery mildew. Remove any small affected parts of the plant and treat affected areas with an organic fungicide or neem oil.

Verticillium wilt can also be a problem, and, usually, it's best to remove affected plants and their roots to prevent spread.

Common Problems with New York Asters

If you want to keep your New York asters looking their best, watch out for these early warning signs that you're getting something wrong with their care.

Flopping Stems

Division of New York asters every few years is important to retain healthy plants. If you spot flopping stems, it could be because they are overcrowded or because you are overwatering.

However, sometimes, tall cultivars experience flopping stems no matter how healthy they are, and staking is necessary.

Leaves Turning Yellow

Yellowing leaves on your New York aster can indicate various problems. Most commonly, it relates to a light or watering issue.

If your plant gets too much water, it can suffer from root rot. Alongside yellow, wilting leaves, you might see a sunken and brown crown and flopping stems.

If your plant has been left without water for too long, especially when conditions are very hot, sunny, and dry, this can also turn the leaves yellow. They might also be scorched, curling, and brittle.

Brown Leaves

Powdery mildew, a common problem with overcrowded New York asters, can result in brown, shriveling foliage. Remove infected leaves, treat them with a fungicide, and divide them to deal with poor air circulation caused by overcrowding.