Zinnias are easy to grow, do well in most environments and look fantastic. They’re a favorite for good reason.
And on top of that propagating zinnias is really straightforward, for both growing from seeds or cuttings. So you can easily have a garden with lots of lovely blooms throughout the season.
This simple guide will walk you through everything you need to know, with easy to follow steps that will help you maximize your success.
Getting Ready: Tools and Supplies
Before beginning the propagation process it’s a good idea to make sure you’re well-prepared. Here’s a checklist of essentials:
- Zinnia seeds (or plants if you’re taking cuttings)
- Seed trays or small pots
- Rooting hormone (for cuttings)
- High-quality potting mix or seed-starting mix
- Sharp, clean pruners or scissors
- Labels for tracking different varieties
- Compost or organic mulch
- Spray bottle (for watering seedlings or cuttings)
Propagation by Seeds
Direct Sowing vs. Starting Indoors
Growing zinnias from seeds is one of the simplest and most rewarding ways to fill your garden with these beautiful flowers. There are two methods: direct sowing into the ground and starting seeds indoors.
Direct Sowing
- When to sow: Wait until the danger of frost has passed and the soil has warmed to at least 60°F. This is typically in late spring.
- How to sow: Prepare the soil by loosening it with a garden fork or tiller and make sure it’s free of weeds. Scatter the seeds on the soil surface, then cover them lightly with about a quarter or an inch of soil.
- Watering: Lightly water the soil immediately after sowing. Keep the soil consistently moist (but not waterlogged) until the seedlings emerge in about 7 to 10 days.
Starting Seeds Indoors
- When to start: Begin sowing 4-6 weeks before the last frost date. Place the seed trays or pots in a warm, bright location.
- Soil preparation: Use a high-quality seed-starting mix. The soil should be moist but not overly wet.
- Light and heat: Place the seeds under grow lights or in a sunny window and consider using a heat mat to ensure the soil stays warm (65-75°F). This will speed up germination, which usually occurs within 5 to 7 days.
Transplanting Seedlings
Whether you’re direct sowing or starting indoors eventually your seedlings will need to be thinned or transplanted to their permanent location.
- Ideal timing: Transplant when the seedlings have at least two sets of true leaves and nighttime temperatures remain above 50°F.
- Spacing: Space seedlings about 6 to 18 inches apart, depending on the zinnia variety. This allows good air circulation which is key in preventing fungal diseases.
- Soil prep: Mix in compost to improve fertility and drainage. Zinnias prefer slightly acidic to neutral soil (pH 5.5 to 7.5), so test your soil if necessary.
Propagating Zinnias from Cuttings
Why Cuttings?
Cuttings are a fantastic method if you want to replicate the exact traits of a favorite plant whether it’s the color, height or other characteristics. This technique also eliminates the germination phase making it a faster route to mature plants.
Step-by-Step Propagation by Cuttings
- Selecting Your Cuttings: Choose healthy stems from zinnia plants that have not yet flowered. Cut about 4-6 inches of stem just above a leaf node. This node is where new roots will form.
- Preparing the Cuttings: Remove the lower leaves from the cutting, leaving only the top few. If you wish dip the cut end into rooting hormone to encourage faster root growth.
- Planting in Water or Soil: You can propagate zinnia cuttings either in water or directly in soil:
- Water: Place the cutting in a jar of water and avoid submerging any of the leaves. Keep the jar in a warm spot with indirect sunlight. Change the water every 2 to 3 days to prevent stagnation and promote root growth.
- Soil: Alternatively plant the cutting in a small pot filled with moist potting mix. Keep it in a warm, well-lit area but avoid direct sunlight.
- Caring for the Cuttings: Whether in water or soil roots should start forming within a week. Once the cuttings have developed a healthy root system (usually after 2 to 3 weeks) they can be transplanted into the garden.
Care for Young Zinnias
Watering
Zinnias are relatively tolerant when it comes to watering. But they do best with consistent watering, especially during dry spells. Water at the base of the plants aiming for about 1 inch per week. Avoid overhead watering as it can lead to fungal diseases like powdery mildew.
Fertilizing
Zinnias aren’t heavy feeders but they’ll appreciate a light feeding of balanced fertilizer or a good dose of compost. Apply fertilizer once when transplanting and then again mid-season if necessary. Too much nitrogen can lead to lush foliage at the expense of blooms, so be moderate.
Troubleshooting Common Problems
Powdery Mildew
Zinnias are prone to powdery mildew, particularly in humid climates or when they’re planted too closely together. To prevent this make sure there’s good airflow around your plants. If powdery mildew does appear remove the affected leaves and think about using a fungicide.
Pests
Zinnias are deer-resistant but can fall prey to insects like aphids or Japanese beetles. Regular monitoring and hand-picking beetles is often enough to control infestations. Use insecticidal soap for aphids.
Maximizing Blooms
Deadheading
Regularly removing spent flowers, or deadheading, is essential to encouraging more blooms. You can also pinch back young plants when they reach about 12 inches tall. This will encourage branching and give you even more flowers per plant.
Staking Taller Varieties
Some zinnia varieties, particularly taller ones, may need staking to prevent them from toppling over in strong winds. Use bamboo stakes or another gentle support system to keep them upright.
Harvesting and Saving Seeds
To save seeds for future planting leave a few flowers on the plant to mature fully. Once the heads have dried remove them and store the seeds in a cool, dry place for next season.
This is a simple and affordable way to enjoy zinnias year after year.