Zinnias are most commonly grown as annuals which finish flowering when the cooler weather arrives in fall. Zinnias are not usually grown as perennials and will die back in most regions in winter. You can extend their season so they grow all year in tropical and subtropical regions.
Plant zinnia seeds in late winter and have them growing all the way through to late fall. Keep them protected from cold weather when then are young and frosts as they grow.
Zinnias can grow almost the whole year if you start them early by seed but the soil temperatures need to be kept around 65-70 degrees Fahrenheit to allow the seed to sprout. Use a greenhouse or seedling heat mat to allow the seeds to sprout if you live in a cold area.
Common Zinnia varieties include Gold Medal, and Dwarf varieties. They come in amazing colors like hot pink, yellow, red and orange. They brighten up a green corner in your yard or look great in pots.
Zinnias are related to sunflowers and daisies and bring beautiful bright colors to your garden.
How to keep Zinnias growing like perennials
Although zinnias are annuals, they can grow for a long season if you look after them. Here a few tips that will keep your zinnias growing all year.
1. Protect them from frost
Protecting zinnias from frost is essential if you want them to continue to flower and grow all year. Frosts can arrive in early fall and stick around to early or even late spring in some areas. Planting zinnias near brick walls, covering young seedlings with soda bottles or covering with a plastic bag over night are easy ways to protect zinnias from frosts.
2. Start them in a greenhouse
For early zinnias plant seeds and pop them in a greenhouse. You can get small, upright greenhouses from Amazon with 2-3 shelves or use a small seed tray with a plastic cover. You can start zinnias in late winter if the soil temperature can be kept above 65 degrees.
Seedling tray heat mats are an easy way to achieve this at home and can get your seedlings started and established so they are ready to grow flowers in spring.
3. Sub-tropical to tropical weather
The easiest way to keep zinnias growing all year round is to live in a sub-tropical or tropical region. Mild winters and warm summers are perfect for growing zinnias like perennials. I recently bought seedlings in late fall, ready to put into my garden to grow over winter.
Recreating this environment in cooler regions can be done by using a greenhouse.
4. Keep the soil moist but not wet
Zinnias will grow best in moist but not wet soil. They love summer watering but avoid getting the water on the leaves. Avoid overwatering your zinnias otherwise they can suffer from root rot and their leaves can turn black.
5. Give them full sun
To grow zinnias all year they need a full sun position. Grow them in an open area, remove any overhanding branches that might shade the plants and they will grow flowers early and throughout the year.
Plant them in a warm, sunny position to encourage the most flowers possible. They will keep growing new buds from spring to summer. Remove the old flowers to encourage more flowers to grow.
6. Avoid splashing water
Zinnias hate getting water on their leaves and can develop fungal growth or black spots. They are a very hardy plant so can continue to produce great flowers even with some fungal growth on their leaves. Do your best to water them at ground level and surround them with bark mulch to avoid splashing.
7. Plant seeds early
For the best value zinnias and for a long growing season sow them by seed yourself at the end of winter. A packet of seeds will cost less than $5 and give you 50-100 plants to grow at home. They sprout easily and as long as the seed is kept moist they will grow.
If you are starting your zinnias in winter, plant them into seed trays and use a plastic cover to capture the warmth and humidity. This will also protect them from winter frosts.
If you live in a very cold area, sprout them in a greenhouse or even near a bright window indoors. By the time spring arrives you will have zinnia seedlings ready to plant.
You can sow zinnias straight into your garden beds if you wait for spring to arrive but to have zinnias growing all year, start them early in seed trays.
Avoid covering zinnia seeds with mulch otherwise it will block the light and they will not be able to grow.
8. Grow them near a masonry wall
My favorite tip for protecting sun loving plants over winter is to plant them near a brick wall. The bricks will absorb the sun during the day and keep the ambient temperature around the plant warmer overnight. This can help to protect the plants from the cold night temperatures and early morning frosts.
Are Zinnias a Perennial? | Summary
Zinnias are not usually grown as perennials but can be kept growing almost all year round if they are protected from frost. They are easy to grow in tropical and sub-tropical regions where the summers are warm, sunny and the winters are mild.
Zinnias are a great annual flower that are easy to sow, fast growing, bright and beautiful. I always like to fill my garden with bright flowers to contrast the bright green of my lawn and citrus trees. Bright pink zinnias will be making a feature in my garden this year.
I am an accredited practicing dietitian, experienced gardener and a dedicated cook. I love writing and sharing my experience so you can learn from my successes and mistakes.