If you want to grow beautiful, eye-catching flowers with minimal fuss, zinnias are a fantastic choice. Not only are they great for beginners but they also bloom in such a lovely variety of colors it’s impossible not be charmed by them.
Thankfully they’re also not too difficult to grow.
This guide will take you through growing zinnias from seed to bloom with some extra tips based on personal experience and a bit of trial and error over the years.
Choosing the Right Zinnia Variety
Zinnias come in all shapes and sizes -from dwarf varieties that work well in pots to giants that dominate garden beds.
Popular Varieties:
- Dwarf Zinnias (e.g., Thumbelina): Perfect for containers and small spaces, reaching only 6-12 inches tall.
- Medium Varieties (e.g., Dreamland): Great for garden beds, growing 12-18 inches tall.
- Tall Zinnias (e.g., Benary’s Giant or State Fair): Excellent for cutting gardens, growing up to 3 feet or more.
No matter what type you choose there’s a zinnia for every garden. Be sure to match the variety to the space you have available and your what you have in mind for the look of your garden.
When to Plant Zinnias
Timing is everything. Since zinnias are heat loving annuals native to Mexico, they need warm soil to germinate. Here’s what you need to know:
- Soil Temperature: Ideally, zinnia seeds should be planted when the soil temperature is around 70-80°F (21-27°C). Cold soil will stunt their growth or delay germination.
- After Frost: Plant them outdoors after all danger of frost has passed. Zinnias don’t handle frost well at all.
If you’re starting seeds indoors begin about 4-6 weeks before the last expected frost then transplant the seedlings once it’s consistently warm outdoors. A word of caution: Zinnias can be a bit picky about transplanting, so handle them gently.
How to Plant Zinnia Seeds
Planting zinnias from seed is relatively simple. Follow these steps for success:
- Soil Preparation: Loosen the soil with a garden fork and mix in compost for added nutrients. Zinnias prefer well-draining, slightly acidic soil (pH 5.5-7.5), though they’ll tolerate most soil types as long as it’s not soggy.
- Planting Depth and Spacing:
- Sow the seeds about a quarter of an inch deep.
- Space seeds or seedlings between 6 to 24 inches apart, depending on the variety. This will allow for adequate air circulation and prevent diseases like powdery mildew.
- Watering: Keep the soil moist but not soggy. Zinnias need consistent moisture, especially when they’re young, but as they mature they become fairly drought-tolerant. Always water at the base of the plant to prevent fungal issues.
Thinning and Transplanting Zinnias
Once your seedlings are about 3 inches tall, thin them to provide enough space for airflow and growth. Proper thinning also reduces the risk of overcrowding, which can lead to disease.
Here’s a good tip: choose the strongest seedlings and remove any that look leggy or weak. If you hate waste then transplant the extras into containers instead of discarding them.
If you started seeds indoors harden off the seedlings before transplanting. Gradually expose them to outdoor conditions over a week, starting with a few hours of sunlight each day.
Caring for Zinnias
Now that your zinnias are planted here’s how to keep them thriving all season long:
Watering
Zinnias do best with deep, consistent watering, especially in the heat of summer. Water them early in the morning to allow the leaves to dry out during the day, which helps prevent powdery mildew. If possible avoid overhead watering and use a soaker hose or drip irrigation to keep the foliage dry.
Fertilizing
Zinnias don’t need heavy fertilizing but a balanced fertilizer can help if your soil lacks nutrients. Use a general-purpose fertilizer when planting and supplement with organic fertilizer as the plants grow to encourage more blooms.
Mulching
Mulch is a game changer for zinnias. A 2-inch layer of organic mulch like straw or bark will retain soil moisture and keep the roots cool. Mulch also prevents weeds and minimizes soil splashing which can carry disease to the leaves.
Deadheading and Pinching for More Blooms
Zinnias thrive on attention when it comes to pruning. Regular deadheading is key to producing more blooms.
Removing spent flowers will encourage the plant to focus its energy on creating new buds instead of producing seeds.
How to Deadhead:
- Simply snip off the old flower heads with clean garden scissors just above the nearest set of leaves.
- If you’re growing zinnias for cut flowers try cutting long stems for bouquets. The more you cut, the more flowers you’ll get!
For bushier plants pinch back your zinnias when they’re about 6-8 inches tall. This will encourage them to branch out resulting in fuller plants and more flowers.
Common Pests and Diseases
Zinnias are are susceptible to pests and diseases like most flowers and plants. Here’s what to watch out for:
Pests:
- Aphids, spider mites and whiteflies can target zinnias, especially in hot and dry weather. You can deal with them by spraying the plants with water or using insecticidal soap.
- Beneficial insects, like ladybugs, are your best friends in the garden as they will prey on these pests.
Diseases:
- Powdery mildew is a common issue, especially in humid areas or when the plants are too crowded. The best way to prevent it is to water at the base and ensure proper air circulation by spacing your plants.
- Leaf spots and bacterial wilt can also occur but are less common. If you notice signs of disease remove the affected plants promptly to prevent the spread.
Good garden hygiene, such as cleaning up plant debris and avoiding overhead watering, goes a long way in keeping zinnias healthy.
Maximizing Zinnia Blooms
If you’re after a non-stop flower show, consider these tips:
- Pinch back early growth for fuller plants and more blooms.
- Cut often! Zinnias love to be cut, and the more flowers you take, the more the plant produces.
- Extend the season: Sow seeds every couple of weeks to keep fresh flowers coming throughout summer.
Harvesting Zinnia Seeds
Zinnias are great for seed saving. Let a few flowers fully dry out on the plant and then collect the seeds for next year. Keep in mind that hybrids won’t always produce true-to-type flowers. But for the adventurous gardeners this can be a fun way to see what unique flowers pop up the following season!
Final Thoughts
And there you have it! Growing zinnias is both easy and rewarding. Being so low maintenance means you can enjoy your garden and spend less time worrying about them!