Why Won’t Your Aster Seeds Germinate? Causes and Fixes

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Willie writes on small engine repair, landscaping, and lawn care. He owned a professional lawn care business in Alabama for almost 10 years.

1. Low-Quality Seeds

Propagating healthy, vibrant, and strong aster flowers starts with seed selection. High-quality seeds have a higher germination rate and produce healthy, hardy plants that produce more blooms.

Low-quality seeds, on the other hand, take longer to germinate and might not even make it through the process.

How To Fix

Purchase your aster seeds from reputable sources such as certified nurseries or seed companies specializing in these varieties. You can also get them from online stores that have good ratings.

Check previous customer reviews to avoid wasting money on poor-quality seeds with low germination rates. Take note of the expiration date and opt for freshly prepared seeds with the longest shelf life. The germination rate decreases exponentially with time.

2. Poor Storage Conditions

Aster seeds carry the embryo of the plant and thus should be kept in the best possible conditions to ensure successful germination (source).

Generally, a cool, dry place away from direct sunlight and moisture is ideal for storage. Exposing your aster seeds to high temperatures, moisture, and light can cause them to rot or lose their vitality.

How To Fix

To keep your aster seeds in the best condition, store them in airtight containers and place them in a cool, dark place. You can also store them in a refrigerator or freezer, provided you maintain consistent temperatures.

Also, label the containers with the date of purchase and the germination period for easy reference. However, it’s best to buy aster seeds when you’re ready to use them so they won’t go bad.

3. Inadequate Pre-Sowing Preparation

Soaking your aster seeds in water before sowing helps to soften the hard outer coating and allows them to take up moisture. This vital step helps to speed up and enhance the germination process. The epicotyl will easily break through the hard seed coat, giving birth to the new plant.

How To Fix

Soak your aster seeds overnight in warm water before planting. This will give the seeds a head start and help kick-start germination. Maintain the temperature of the water at approximately 60-70°F (15-21°C) for best results.

Soak the seeds in manganese solution (link to Amazon) for 2-3 hours to eliminate fungal parasites that would compromise your aster plant’s health. You don’t need to scar or nick the seed coat since they are easy to germinate when pre-soaked.

4. Poor Drainage

Asters need well-draining, moist loamy soil to germinate. Poor drainage leads to waterlogging of the soil, making it difficult for oxygen to reach the seeds. This causes them to rot and die instead of germinating.

How To Fix

Use a light, well-draining potting mix or loam soil for sowing your aster seeds. You can purchase potting mix from your local garden center or make your own DIY potting mix. Add perlite, peat moss, and compost for well-aerated soil. A layer of gravel or stones will also help improve drainage.

Provide adequate water when sowing and during germination. Water the soil until it is saturated but not waterlogged.

You can also mend the soil by adding well-decayed compost or organic matter. This holds moisture and improves aeration, making it easier for the seeds to germinate (source).

Additionally, invest in a soil pH tester to ensure your soil is within the desired range. A pH of 5.8-6.5 is ideal for most aster varieties (source).

5. Improper Planting

Planting aster seeds isn’t just adding them to the soil. It’s a delicate technique that requires precision, or you risk damaging or killing the seeds.

Asters need light to germinate, so you should sow them at a shallow depth of ¼ inch (0.6 cm) or less. Planting them too deep can cause them to rot and die before they can sprout.

How To Fix

Here’s how to properly plant your aster seeds:

Gently scatter your aster seeds over the soil in a container or tray.
Spread a thin layer of soil, no more than ¼ inch (0.6 cm) deep, to cover them. Gently press down on the seeds to ensure they are in contact with the soil.
Water and mist the seeds lightly, but don’t drench them.
Place a thin sheet of plastic wrap or glass over the top of the container or tray to create a mini greenhouse. This will keep the soil warm and moist until the seeds germinate.
Once they sprout, remove the plastic wrap or glass and place them in a sunny location.
Provide adequate sunlight (at least 6 hours of full sun per day) and water.

6. Unfavorable Temperatures

Like other plants, asters have an Optimal Temperature Range (OTR) of 64-68°F (18-20°C) for germination. Temperatures outside of this range can affect germination.

Extreme cold temperatures can cause the seed to remain dormant until temperatures are more favorable, while high temperatures can cause them to dry out and die.

How To Fix

Timing is key when it comes to sowing aster seeds. Plant them during the spring or fall when temperatures are more favorable. You can also start them indoors a few weeks before the last frost date.

This gives them a head start and ensures they are ready for transplanting to the garden when temperatures are more favorable.

Provide adequate light and water to the seedlings while they are indoors. Gradually acclimate them to the outdoors by exposing them to increasing periods of sunlight and temperature over a few days (source).

Plant your seedlings in the garden when temperatures stay within the OTR range.

Final Thoughts

Germinating aster seeds is a relatively easy process, provided you take the right steps. Poor drainage, improper planting, and unfavorable temperatures can all prevent your aster seeds from germinating.

Combat these issues with the right soil mix, accurate planting technique, and timely sowing.

Recommended Reading:

How To Keep Your Asters From Getting Leggy