Why Seeds Sulk: How the Equinox Affects Plant Growth & Germination

Understanding the Equinox and Its Importance

You’ve done everything right—sown your seeds, watered them, and kept them warm—but still, nothing happens. Your seedlings sit there, looking miserable and refusing to grow. Meanwhile, someone else sows the same variety a few weeks later, and their plants take off like rockets. So, what’s going on?

If this has ever happened to you, you’re not alone. The secret to when seeds thrive and when they sulk lies in something many growers overlook: the Equinox and how plants respond to daylight.

I’ve learned this lesson the hard way: sowing too early and watching my seedlings struggle before waiting just a little longer and watching them thrive. Timing really is everything. Today, we’ll discuss photoperiodism (don’t worry, it’s not as complicated as it sounds), why some plants refuse to grow before the Equinox, and how you can time your sowings perfectly for stronger, healthier plants.

The Equinox - Nature’s Green Light for Growth

The Equinox is the point in the year when day and night are exactly equal in length. It happens twice a year—once in spring and once in autumn. From this moment on, the daylight hours change significantly, impacting plant growth directly.

In the Northern Hemisphere, the Spring Equinox occurs around the third week of March. From that point forward, the days get longer, signaling many plants to start growing properly. Conversely, the Autumn Equinox occurs around the third week of September when daylight hours begin to decrease. So, why does this matter for sowing seeds? Plants don’t check calendars, but they do track daylight.

My Own Equinox Growing Mistakes (And What I Learned)

I've been guilty of sowing too early—thinking I was getting ahead of the game—only to end up with sulking seedlings that refused to grow.

This year, I sowed statice a week before the Equinox. By the time it germinates and starts growing, we’ll be at the perfect point in the season for strong growth. Once my statice is off the heat mats, I will move on to sowing cosmos and zinnias—but only because I've learned my lesson the hard way.

I used to sow cosmos and zinnias too early, thinking I was being proactive. However, they just sat there, not growing properly until much later in the season. By that time, they were already stressed, leading to weaker plants and delayed blooms.

I’ve also just sown dahlias, again a week before the Equinox, with plans to put in another batch just after. Since dahlias can take weeks to germinate, this timing means they’ll emerge when daylight hours are naturally increasing.

While dahlias are wonderful, here’s the golden rule: they MUST be kept indoors and away from frost. If they get cold, you’ll lose them before they even start. Aligning your sowing schedule with the Equinox will help your plants become stronger, healthier, and quicker to grow.

Why Some Plants Refuse to Grow Before the Equinox

Not all seeds are the same. Some plants thrive in longer days, while others prefer shorter days or aren’t affected by daylight at all. This is where photoperiodism comes in—plants’ ability to measure day length and respond accordingly.

Plants fall into three main categories:

1. Short-Day Plants (Need long nights to flower)

• These plants will delay blooming or refuse to flower if the days are too long.

• Examples: Cosmos, Celosia, Zinnias, Dahlias

• Best sown after the Equinox for optimal growth.




2. Long-Day Plants (Need long daylight hours to trigger flowering)

• These plants need longer daylight hours before they bloom properly.

• Examples: Statice, China Asters, Strawflowers

• Thrive after the Equinox when days are naturally longer.




3. Day-Neutral Plants (Grow regardless of day length)

• These plants aren’t affected by day length at all. Instead, they respond to maturity and temperature.

• Examples: Tomatoes, Cucumbers, some varieties of Sweet Peas

• Can be sown earlier, but still need warmth to thrive.

If you plant a long-day flower too early, it won’t do much—it’s waiting for the right daylight signals.

How to Time Your Seed Sowing for Success

Wait until after the Equinox for:

• Cosmos

• Zinnias

• Sunflowers

  
  

Hardy Flowers That Can Be Sown Before

These flowers can be sown from Autumn through winter and into spring:

• Sweet Pea

• Snapdragons

• Poppies

• Larkspur

  
  

Slow-Growers That Need a Head Start Indoors

Some flowers require more care. These slow-growers include:

• Lisianthus

• Eucalyptus

• Ranunculus

  
  

🎧 Listen to the Podcast for More Insights!

Want to dive deeper into why day length matters for plant growth? I share real-world examples, expert tips, and even more sowing strategies in my latest podcast episode. Listen now → PODCAST

Have you ever sown something too early and had it sulk? Tell me in the comments—I’d love to hear your experiences!

Happy growing!