Will A Frost Knock Out Your Zinnia Flowers?

frost on pink zinnia petals

With as many qualities as zinnias have going for them, it’s no wonder you might want to stretch their growing season as long as possible. The prolific and beautiful blooms are perfect for bouquets, making zinnias a shoo-in for the cutting garden.

But to get the most from your zinnias, make sure you plant them when they’ll survive cold weather.

Zinnias are classified as a tender annual, so they will not survive a frost. The plants must be grown during the summer season in the window of time between spring and fall frosts. If a frost is expected while the plants are still blooming, a row cover can provide some protection.

When can I put zinnias outside without risk of frost?

Zinnias can be put outside as seeds or transplants once all risk of frost has passed in the spring. They can be planted continuously through the summer until it gets too late for them to have time to bloom before the first fall frost.

That window of time is known as your frost-free growing season. For many US flower gardeners, that time frame is somewhere between April and October. It will vary depending on where you live, and even different areas of the same town can vary due to the surrounding environment.

Frost is the kiss of death for zinnias.

To get an estimation of your growing season, look up your last and first frost dates on Farmer’s Almanac. Remember that this is only a general guideline, as some years frosts appear later or sooner than expected. Mother Nature likes to surprise us gardeners sometimes!

As a defense against frosty, zinnia-killing weather, try using a row cover to buy yourself some extra growing season. A row cover is a piece of plastic or plastic fabric material (woven polypropylene) that acts as a mini-greenhouse and keeps the air temperature around the plants just a couple of degrees warmer than the exposed air.

The temperature difference can be enough to keep the frost from killing your zinnias, whether at the start of the season with young transplants or the end of the season with established, blooming plants.

If a row cover sounds like something you’re interested in trying, I also wrote this post, Will A Frost Kill My Cut Flowers?, where I discuss row covers in more depth, as well as other options to try if you want to keep the frost off your zinnias.

Quick blooming zinnia varieties for when your frost date isn’t far away

If you live in an area with a short summer season, there are varieties you can plant in your garden that will reach maturity sooner than others. If you have around two months until your first fall frost, then you can squeeze in some zinnia blooms.

Zinnia varietyColorDays to maturity
Pumila Mixred, orange, yellow, pink60
State Fairred, orange, yellow, pink65
Oklahoma Salmonsalmon-pink75-90
Queen Series Mixlime, rose, rust-orange75-90
Polar Bearwhite75-90

Some varieties will bloom right around 60 days after sowing, such as the Pumila Mix zinnias. This variety has smaller, single blooms in cheerfully bright red, pink, yellow, and orange colors. A similar variety, State Fair, has small blooms in the same shades and will show its first flowers 65 days after planting.

Most zinnias will bloom 75-90 days after planting, so you’ll find a much wider range of flowers in this category. Even though they take a little over two months to mature, you’ll still have time to harvest loads of blooms before a frost kills the plants.

You can find zinnias in this maturity category in a huge range of colors, from spiky pink blooms to puffy white spheres to small daisy-like ombre petals. There’s almost no limit to the color palette that’s possible with zinnias!

Here are a few of my favorite, some of which I have in my seed packet collection right now, waiting to go in the garden.

  • Queen Lime Orange: This member of the Queen Series produces rusty orange blooms with big, round flowers.
  • Oklahoma Salmon: A cupcake-shaped zinnia, the salmon-colored blooms perform very well in the vase.
  • Jazzy Mix: With great fall colors of deep red, orange, and gold these zinnias are great for mid-summer plantings.

There are so many more varieties to choose from. The challenge isn’t finding varieties to grow before a frost, but instead finding room in your garden for all the different types!

Alternatives to zinnias that can survive a light frost

If you want to hedge your bets and plant a few other types of flowers that can handle a light frost, then there are options for you. All of these alternatives will also eventually die as winter brings colder weather, but they’ll help extend your blooming season once zinnias have given up the ghost.

Calendulas and marigolds are two options that have the same ball-shaped bloom as a zinnia. Both types of flowers tend to be yellow, gold, orange, and red shades, so if you are looking for a pink or purple alternative, you won’t find it here.

Here are some calendulas and marigolds that are great in the flower and cutting garden:

Flower varietyColorDays to maturity
Playtime Mix calendulayellow, bronze, cream55-65
Orange King Calendulaorange55-65
White Swan marigoldcream65-75
Nosento Limegreen marigoldpale yellow80-95

If you are only concerned with having flowers and don’t mind that they look different from zinnias, then give dianthus and pansies a try. Bonus, they are available in colors more similar to some zinnia offerings, such as pink, red, and purple.

Flower varietyColorDays to maturity
Nature Antique Shades pansiescream, blush, gold70-80
Majestic Giants pansiespurple, yellow, violet90
Sweet Black Cherry dianthusdeep red100-105
Chibaud Picotee Double Mix dianthuspink, purple, salmon, cream130-140

Even though zinnias will not survive a frost, if you use a few different methods, from row covers to alternative varieties or some mix in between, you’ll still have a productive zinnia patch for a large part of the year.

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