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When Is It Too Late To Plant Aster Seeds?

When Is It Too Late To Plant Aster Seeds?

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Willie Moore
Latest posts by Willie Moore (see all)

Asters have been found to grow well in all seasons of the year. However, planting them is a process that must be well-calculated and performed promptly in order to ensure the healthiest plants possible.

You should always plant aster seeds no later than June or early July. Not only to ensure they get in the ground before the temperature increases rapidly but also because you must plant them before they start to bloom in September and October.

In this article, I’ll discuss when it’s too late to plant your beautiful asters and why this is something to consider in the planting process. Additionally, I’ll cover how you can get a head start in preparing for the planting process by growing your asters indoors.

When Is the Last Month To Plant Aster Seeds?

To get gorgeous asters that are at their peak health, you must plant their seeds in early summer, around June or July at the latest. In some cases, you can try to plant them a little later, but this may not guarantee a strong set of plants in the end.

You must plant asters in June or July at the latest because they need to be ready and adapt to their new planting placement before their blooming season. On average, most aster species bloom in early fall, around the first few weeks of September (source). 

In some cases, asters will bloom a little later in late September or October, but it is always best to anticipate this growth for early fall. This time is just cool enough for them to stay open and well in more manageable weather. 

Why Should You Plant Aster Seeds by June or July?

Research conducted on the study of different temperatures on asters identified that the best growth periods are when temperatures are lower and not excessively warm (source).

This data asserts that you must plant aster seeds at the time of the year right before it starts to get hot. Not only does this allow for an adjustment period for asters to get regulated after being planted, but it also gives them time to increase before the heat gets more aggressive. 

Typically, summer heat peaks around July and carries into August, depending on the area (source). In order to have your asters ready to take on this increase in heat, they have to spend some time in the heat right before it hits the higher temperature points.

Starting asters are just at the beginning stages by the time they are first planted in June or July. To successfully sustain good health and prepare for blooming, they must be allowed time to get taller and studier. 

With some types of aster plants, the early stages of blooming can possibly happen in August when it’s still pretty hot out (source). However, regardless of the type, aster seeds should be planted in early summer or even earlier in the spring months of April and May to have the best success for steady growth. 

What Other Conditions Are Best for Planting Aster Seeds?

In addition to planting aster seeds in a timely manner, you must also plant asters with the right soil and watering conditions. 

To achieve the best growth for your asters and ensure that they will survive the blooming season, they must be kept in rich soil and areas with either full or partial sun exposure (source). Doing so will provide the right environment for asters to thrive in without jeopardizing their overall health.

Even though some asters have been found to grow proficiently in cooler or heavily shaded areas, all asters need sun exposure for at least half of the day (source).

Many issues can occur if you do not provide the correct amount of sun exposure. For example, not enough sun will lead to quick wilting, while too much will lead to dry or crunchy plants. 

Additionally, you must plant asters in a way that allows them to have room to expand. 

On average, asters have extensive roots reaching two to four feet (0.6 to 1.2 meters) after they have fully spread out (source). Therefore, if individual plants are planted near one another, there may be issues with their roots, or the space will be very overcrowded as they push against one another. 

In addition to perfect soil and sunlight, you should water asters semi-frequently to ensure they are not dehydrated or oversoaked. As long as you set time to water them once or twice a week, they will be sure to keep growing and stay healthy. 

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

Can You Grow Aster Seeds Indoors?

Aster seeds can be grown inside, though this is usually just a preparation for planting rather than sustainable long-term placement. Growing asters indoors helps them develop and have a healthy start before planting them in a larger area outdoors. 

Usually, asters are only grown outdoors because of their size and how much their roots extend. However, growing them indoors for a temporary amount of time can allow them to develop into hearty sprouts. 

When growing asters from seeds indoors, they should be kept in suitable pots or gardening containers until they are about five to eight inches (12 to 20 centimeters) tall (source). However, if you want to leave them in their pots until they are a little larger, you can leave them for an extra few weeks if necessary. 

Whether grown indoors or outdoors, asters still need the right conditions and sun exposure to help them grow strong. Additionally, to reduce tampering and destruction, you should keep them in an area that is out of the way of threats, such as household pets or small children.

Final Thoughts

Asters typically grow on a predictable schedule according to weather, seasons, and temperature. 

To avoid planting your aster seeds too late in their growing process, plant them any time before June or July. Doing so prevents them from failing to bloom on time and allows them to grow a bit before placing them directly into the ground. 

Sometimes, however, you may be unable to plant on time because of unforeseen circumstances, or the developed aster seeds are not ready to be moved outdoors. As long as you plant your asters before July ends, they may still thrive and flourish.

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