Does Zinnia Need Full Sun To Grow?

Zinnias have a classical beauty that makes them blend perfectly in any garden. The only hiccup here is whether or not growing in the shade of another tree is something these flowers are capable of doing. So, does zinnia need full sun to survive?

Zinnias need full sun not only for optimum growth but also to prevent diseases ranging from mildew to fungal infections. However, they are hardy and could tolerate partial shade, especially in warmer regions.

In this post, we go over the elegant zinnia’s sunlight needs for outdoor and indoor planting. We’ll also cover the flower’s compatibility with artificial grow lights. Let’s get started!

Does Zinnia Need Full Sun To Thrive?

Caring for a plant is much easier if you understand the science behind it. Don’t worry, though. We won’t get into complicated jargon.

The gist of it is that there are two main reasons why zinnias are the sun-loving plants that they are. Let’s take a closer look:

1.   Full Sun Boosts the Growth Rate

Sunshine is a crucial part of any plant’s growth rate and flowering potential. Even more so for annual plants. Those have quick cycles that can be thrown off balance with even the most subtle changes.

Zinnias that grow in shade will be less likely to produce healthy flowers. That’s if they bloom at all.

Plus, you can’t expect the zinnia to reach its ideal height (around four whopping feet) without something as essential as enough sun time.

2.   Full Sun Keeps the Diseases Away

Zinnia, like any other outdoor plant, is susceptible to a wide range of infestations, including aphids, mites, mildew, and verticillium fungus.

A combination of adequate sunning, high drainage, and good air circulation can help the plant fight these pests and infections.

That’s because cool, shaded, and humid areas encourage fungal and bacterial growth, which will eventually wear the plant down.

How Much Sunlight Is Enough for an Outdoor Zinnia?

Let’s start by saying that it’s very hard to expose zinnia to too much sunlight. While reduced sun exposure can harm the plant, you don’t have to worry about heat burns at all.

They adore the sun and are also extremely heat tolerant. Those hardy flowers will handle up to a 100°F as long as you water them regularly.

The challenge is to find the minimum amount of sun time that you can’t drop under. If you’re going for direct sunlight, aim for at least six hours of daily sunning.

Keep in mind that the entire period between sunrise and sunset doesn’t count in full. In most outdoor planting beds, you’ll get morning shade and afternoon sun.

To put it simply, you might need anywhere between 6-12 hours of daylight. It all comes down to where you choose to put the zinnia in the garden.

We recommend a south or west-facing flower bed for maximum effect. That’s not all. You’ll also need to check that nothing is getting between the zinnias and air circulation.

Would a Zinnia Tolerate Heat Well?

Zinnias aren’t just capable of surviving intense sunlight. They are overall well-adapted to survive summers in warm climates, too.

It’s actually the frost that you should be worried about. If you get harsh winters where you live, you might need to move the potted flowers indoors. That’s a whole hassle, but we’ll get to that in a minute.

For optimal temperatures, zinnias need a daytime range of 75-85°F. You can always check the general climate compatibility through the USDA hardiness zones.

Zinnias can grow almost everywhere in the United States, but they’re better acclimated to zones 7-9. They’re quite versatile and drought-tolerant species!

What Happens if Zinnias Don’t Get Enough Sun?

If Zinnias don’t get enough sun, they become weak and become susceptible to fungal infections. The flowers will not bloom and the infections will cause the plant to die.

If you want to save your zinnia plant from dieing, make sure to place zinnias in direct sunlight. If the weather conditions are not good or its cloudy from days, check for the fungal growth in zinnias.

• Zinnias growth stops, if they don’t get enough sunlight.
• Lack of sun causes several bacterial and fungal infections in plants.

Can Zinnias Grow Indoors?

It’s possible to grow zinnia in pots, and they can germinate from seeds without hassle. However, when you’re trying to grow zinnias indoors, the real challenge is getting the full sun part right.

Start by planting the seeds from any zinnia growing kit 5-7 weeks before the late-spring frost. Try to keep the soil temperature around 70-80°F. Use a heating mat if your home is on the cold side.

You can try to keep the plant in a window that receives the most sunlight, but it won’t be as efficient as outdoor beds, though.

For instance, six hours of direct sunlight are enough. Meanwhile, you’ll need to push that to around eight hours of indirect light to make up for the lost intensity.

Another crucial aspect to consider is the drainage. Excess water can accumulate in planters and encourage root rot. So, be sure to find a pot with bottom holes and fill it with porous soil.

You might also need to fertilize every other week to keep the soil rich. You don’t want to risk any imbalance, from soil to sunning time. Moreover, you can pump your chances by using grow lights.

Can Zinnias Thrive Under Grow Lights?

Grow lights are quite a handy tool for indoor gardening. They can open up the door to grow plants even if you don’t have the ideal sunlight-shade balance.

Unlike regular lamps, a grow light covers a wider range of warm and cool ends on the spectrum. This is essential for mimicking the effect of natural sunshine on plant growth.

When you’re planting indoor zinnias, growing lights can provide an extra boost of artificial sunning. However, you’ll need to know how to pick the right one.

The relationship between a plant’s needs and the efficiency of an artificial grow lamp can be measured in terms of Day Light Integral (DLI) and Photosynthetic Photon Flux Density (PPFD).

To put things in perspective, the peak DLI for zinnias is 12.5 mol.m^-2.d^-1. We won’t bore you with the calculations, but at six hours, you need a grow LED that can go up to 550-600 PPFD.

If you get one with higher intensity, make sure it’s dimmable. Alternatively, you can go for weaker lights if you increase the operation period.

It’s an overall decent option, but nothing beats the natural sunshine for the zinnia!

Conclusion – Does Zinnia Need Full Sun?

You can grow zinnia in your backyard and it can grow well in sun as well as in partial shade. But when it is grown in sun where it receives more than 6 hours of sunlight, chances of being susceptible of infestations and fungus reduces. However, you can zinnia indoors under artificial grow lights.

Frequently Asked Questions

Can I grow zinnia in shade?

You can grow zinnia in shade where it can receive partial sunlight or under grow lights. But, you will have to look out for infestations that may come due to not getting enough light.

How many hours of sunlight do zinnias require?

Zinnias require at least 6 hours of sunlight for nice growth. It also need well draining fertile soil for perfect bloom. If it doesn’t receives proper light, you will see less flowers.

Do zinnias do better in pots or in the ground?

You can grow zinnias in pots, wooden half-barrels or a hanging basket but it must have a hole for water drainage to prevent fungal growth in soil.

Why are my zinnias dying?

If you are living in a warmer climate, your zinnias can die due to lack of water. The leaves will shrivel and turn brown. However, they may also die due to fungal growth when they don’t receive enough sunlight and don’t have a proper water drainage.