Why Are Sunflowers Tall? Here’s Why!


Sunflower Chat / Tuesday, October 30th, 2018

When we picture a sunflower, we all seem to have in our minds this idea of a tall, straight stem, with occasional large green shapely leaves. Large, round, yellow petalled, bright, happy looking sunflower head shining brightly at the top.

It’s the stereotypical image we all have, even from childhood. And in many cases, this is true. Its what drew me to sunflowers in the first place. But why do they grow so tall? Let’s look a little closer into this.

So, Why Are Sunflowers Tall? There are many varieties of sunflower, the most common depiction of this species is the tall large headed sunflower. The scientific term for it is Helianthus Annuus. This particular species is known for its tall proud height. Extending some 2 meters tall, or more in ideal growing conditions.

In fact, we often use the height of the sunflower to ascertain how successful our growing of it has been. Whilst it’s common to see height as an achievement for a sunflower.

The real achievement lies within the sunflower head itself. In particular, how successful seed production has become. That is what the sunflower strives to achieve. The height is merely a means to maximize seed production.

Why Do Sunflowers Need to Grow Tall?

Sun is of paramount importance for a sunflower. In ideal conditions, they need at least 6 hours of sunlight a day to stimulate photosynthesis to increase growth rate.

For this, we could possibly also refer to Darwin’s theory of evolution to see why the sunflower strives for height as an important factor in its growth.

The strongest will thrive – so to speak! In a world where all (or at least most) plant life is dependent on sunlight for growth, the sunflower has evolved over time to reach the tallest it can. In so doing it can. We only need to refer to the canopy in the Amazon Jungle to see the fight for sunlight. Sunflowers have simply learned to do the same.

The real achievement lies not in the height, but within the sunflower head itself. In particular, how successful seed production has become.

Suffice to say, sunflowers don’t ‘need’ to grow tall. They can survive perfectly well in most cases if they’re smaller, and many species do. But, being the tallest means they’re likely to have greater access to more sunlight. Therefore, it’s just a natural instinct.

Why Is Sunlight Important For a Sunflower?

For the same reason that it’s important for most plants. Sunlight stimulates the act of photosynthesis. This reaction multiplies cells and increases cell growth rate to further develop the plant.

Do All Sunflowers Grow Tall?

Actually, no they don’t. In part, due to human intervention. Rightly or wrongly, many species, (or variants) of sunflower are now designed to perform a range of functions, or indeed to blend into different environments better.

For example:

  • Seedless Sunflowers, such as the variety ‘Junior’, are now cultivated for indoor use, they do not produce seeds and therefore there is no issue with pollen. Ideal for flower arranging and indoor use where pollen can be an issue for humans.
  • Dwarf Sunflowers, such as the ‘Elf’ variety now form a large part of the sunflower population, again ideal for small garden use in pots or indoor arrangements. Growing up to 16 inches and in a variety of stunning colors. 
  • The Morden’ variety is popular in India in particular for its high oil yield.

This isn’t the case for all sunflowers, many have simply evolved into their own individual habitats and their requirements for growth have evolved with them.

Does Lack of Sunlight Affect The Growth of a Sunflower?

The correct answer is yes, and no! Sunflowers are hardy species, growing fairly easily in temperate to warm climates that can range in temperatures quite significantly. Growing them outside of summer months is certainly possible. As long as temperatures are moderate …and certainly not freezing!

However, like most ‘growing things’, its growth is affected by the amount of sunlight it can obtain. A more cloudy, cold or low temperate climate will likely yield a shorter plant, with fewer seeds produced. However, these variations can be minimal.

Minimal, mainly due to the nature of how the sunflower absorbs sunlight via Heliotropism. I wrote a really interesting article on this called Do Sunflowers Follow The Sun. I’d strongly recommend reading that so you can impress your friends with some new-found knowledge!

I’d strongly recommend reading that so you can impress your friends with some new-found knowledge!

How Do I Ensure My Sunflower Grows Tall?

There are a set of ideal temperatures that you should ideally grow your sunflower in for maximum growth in height, flower head size and seed yield. You can read more about those in my Ultimate Guide To Growing Sunflowers

I’ve provided a quick rundown here, but for a full guide to growing your sunflower please refer to my resource page.

  1. Summer months are the optimum time for your sunflower to grow. Planting from the end of May (in the northern hemisphere) and end of October in the southern hemisphere will ensure you catch the best of summer sunshine and warmth, and miss the last of the winters ground frost.
  1. Allow a width of around 2 feet from another sunflower or other plants. Plant in an area of soil that is well-drained, and at least 2 feet in depth.
  1. Sunflowers are generally deep-rooted plants. They need to be provided with a sufficient anchor to support the height and they can be thirsty friends. So ideally, the ground needs to have been left fallow for a year before-hand so that groundwater stocks can be replenished. Or, ensure you thoroughly water your sunflower to provide sufficient nourishment.
  1. The path to sunlight is obviously a factor. For best results, ensure your little yellow sunflower friend can see the sun from as far in the East as possible in the early part of the day. To as far as possible to the West.

    If this is not possible, then at least try to ensure it has a good amount of sun as early as possible in the day and for as much of the day as possible.
  1. If planting out shortly after rooting, ensure you provide it with sufficient netting or protection from rodents and insects to enable it to establish. Keep weeds at bay and water frequently.

As mentioned, for a full guide, see HERE.

Where Can I Buy The Tallest Sunflower Seeds?

If, as I suspect, you’ve arrived here with sunflower shaped eyes, looking to grow the tallest sunflower possible, then I’d be wrong not to give you my recommendation. For this, I’ve chosen one that is easy to grow (so it’s better for kids too) and is fairly hardy.

The one I’d recommend is the Skyscraper Sunflower, which can grow up to around 12+ feet tall in the right conditions. You can find it on Amazon here.

Or, if you’re looking for an ‘all-in-one’ activity to do with your kids, (and where height isn’t necessarily the important factor), then you could go for this cute sunflower growing kit on Amazon. It’s a great little gardening activity!

In Conclusion

Sunflowers are tall mainly because they evolved that way. One thing I find unusual is that it’s one of the few species of flowering plants to take height as a serious factor for gaining best results. So why don’t all plants do this?

The other amazing factor for me is that Sunflowers are a natural part of the Daisy Family of plants. And yet we know that most daisy varieties grow small, in general. So at what point did the sunflowers decide they wanted (or needed) to be taller?

Perhaps We’ll never know…

Nonetheless, to me, sunflowers just would not be the same without the height that (generally) comes with them. Even the smaller varieties have a ‘tallness’ to them. It’s almost as characteristic as the large sunflower head they produce.

The tallness factor for me makes them look even more majestic. Standing tall and proud and reaching up into the world as high as they can. There’s a lesson in there for all of us, perhaps…

I hope this has helped to clarify why a sunflower grows tall and perhaps, how to get your sunflower to grow as tall as possible. Or just how high a sunflower grows!

Related Questions

How Tall Will My Sunflower Grow? The height your sunflower grows will depend on a number of factors. Variety is the largest determinant of height. Most varieties can grow from 15 inches to 15 Feet in height. Other factors include climate, sunlight, water, and general care.

What Is The Largest Sunflower? According to the Guinness book of records. On 28th August 2014, Hans-Peter Schiffer of Germany, a previous three times record holder for the largest sunflower, grew a sunflower that was recorded at 30.1 feet tall, or 9.17 meters!

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