Zinnia seedlings are the first set of leaves that emerge after germination. They are highly valued by gardeners because it helps give a perfect start to growing these annual flowers. Seedlings are first grown indoors and are later transplanted outdoors when soil warms up. About 1 week after sowing, true leaves start to appear if the proper care is provided, which later accelerates root formation. While these seedlings are prone to pest infestations and transplanting shock, a little care can ensure healthy growth.
If you are intrigued to know more about zinnia seedlings, let me take you through a detailed guide about the appearance of zinnia seedlings along with their growth, care, and common challenges.
Quick answer
Zinnia seedlings are a set of leaves that sprout after germination. Also called cotyledons, they are not true leaves and take at least 4-5 days to emerge. Make sure the seeds are planted indoors 3-4 weeks before the last frost date , at least ¼ inch deep in the soil, and are provided 12-16 hours of grow lighting indoors with 1 inch of water weekly and then transplanted outdoors once all the danger of the frost has passed.
What are Zinnia Seedlings?
Zinnia seedlings are newly emerged sets of leaves, also called cotyledons (embryonic seeds), that grow from the zinnia seeds. It takes almost 4-5 days for the seeds to grow into these seedlings, which grow into the elegant zinnia flower. A healthy set of zinnia seedlings has a small, green, oval shape with a fleshy, plump appearance. These seedlings undergo the process of thinning after they are 3 inches high to snip off the dead leaves for healthy growth.
The difference between a seed and seedling is that the latter is a sprouted version of the former.
How Long Does It Take to Grow Zinnia Seedlings?
It takes 4-5 days for the zinnia seedling to grow cotyledons; then, in 1 week, these leaves expand, a true set of leaves emerges, and by the end of 2 weeks, the roots have strengthened themselves to be ready for transplanting.
Take a look at the different stages of the growth of zinnia seedlings and the time it takes to grow:
1. First Set of Leaves Appears (4-5 days)
Zinnia seeds germinate in about 5 days, after which 1 set of leaves, also known as cotyledons, grows. This set of small oval green leaves is not true leaves but is significant for growth before the roots fully mature and the plant grows true leaves.
2. True Leaves Emerge (1 week)
By the end of 1 week, a new set of true leaves emerges. The difference between the true leaves and cotyledons is that the latter form inside the seeds in the embryo, while the true leaves grow as the plant matures and make food for the plant.
3. Seedling Ready for Transplanting
Zinnia seedlings are ready to be transplanted after 4-6 weeks of growth. The plant roots have developed and are sturdy enough to provide nutrition for the growth of the plant. If you have placed the seedlings indoors, in about 4 weeks, they are mature enough to be transplanted into the ground in a new potting mix.
How to Grow Zinnia Seedlings Indoors?
To grow zinnia seedlings indoors, start by taking zinnia seeds, a seed tray, and some well-draining potting mix. Fill the seed tray with the soil mix, gently place the seeds, and cover them with the soil. Water it consistently until the seedling grows.
Take a look at the step-by-step guide on how to grow the zinnia seedlings indoors before they are ready to be transplanted outdoors:
Step 1: Selecting Seeds
Select healthy and plump zinnia seeds to ensure strong seedlings. Healthy zinnia seeds are flat and shaped like an arrow in a dark brown color. Unhealthy seeds can cause stunted growth and fungal infections.
Step 2: Preparation and Planting
Take a seed tray and fill it with a well-draining potting mix. Place the seeds at least ¼ inch deep and cover them with the potting soil. Water them thoroughly and place them in a grow light. Natural light is often too weak to reach seeds indoors, which can make the plant extremely leggy.
Step 3: First Set of Leaves
In about 5 days, the first set of leaves called cotyledons will appear. They are small, oval-shaped green leaves that are not true leaves but will help the plant form roots and survive until true leaves emerge.
Step 4: Thinning Seedlings
After the seedling reaches 3 inches in height and multiple sets of true leaves appear on the stem, snip off the dead and diseased leaves before transplanting to avoid stunted growth.
How to Transplant Zinnia Seedlings Outdoors?
Zinnia seedlings can be easily transplanted outdoors by preparing the seedlings for the outdoor climate, mixing organic matter into the soil, gently shifting them, and watering them adequately to accelerate the process of root formation.
Take a look at the easy transplanting steps for zinnia seedlings:
Step 1: Preparation Before Transplanting
To avoid transplant shock, water the seedlings well and keep them in natural light for a few hours for 7-10 days to acclimatize them to natural light and air.
Step 2: Site and Soil Preparation
Choose a spot with well-draining soil that receives full sunlight. Before transplanting, make sure the soil is damp, as dry soil can stress the seedlings. You can also add some organic matter to the soil for added nutrition and improved drainage.
Step 3: Place the Seedling
Dig a hole as deep as the root ball of the seedlings and place them gently in the soil. Make sure they are properly spaced with at least 6-12 inches of gap between them to provide proper air circulation and avoid overcrowding. The depth should be the same as that of the root ball to prevent suffocating roots.
Step 4: Aftercare
Water the plants thoroughly throughout the growing season, and look out for waterlogging and browning ends, which can be an indication of a watering issue. The seedling will start to grow and flower in about 6-8 weeks.
What is the Best Time to Plant Zinnia Seedlings?
The best time to plant the zinnia seedlings indoors is 3-4 weeks before the last frost date in your region. You can sow them directly outside after the danger of frost has passed. They prefer warm temperatures and should be planted only when the soil temperature is between 21°C and 27°C. Seedlings have weak roots and hence should be handled with care, as they are prone to transplant shock.
It is generally rare to purchase seedlings directly from a store, as most gardeners start with seeds indoors and then transfer them outdoors when they grow their first set of leaves. If you want to start indoors, April and May are the best times to do that, and then gradually plant the seedlings during late spring to early summer after the danger of frost has passed.
Care Tips For Zinnia Seedlings
To care for the zinnia seedlings, make sure that you provide adequate lighting: 12 hours of grow lights indoors and 6-8 hours of sunlight outdoors, with 1 inch of water weekly, 6-12 inches of spacing, and the process of thinning for proper maintenance and healthy growth.
Take a look at the care requirements of the zinnia seedlings:
1. Lighting
Zinnia seedlings grown indoors require 12-16 hours of artificial light to survive. It is quite difficult to provide direct sunlight to the seedlings growing indoors; hence, grow lights are perfect for their growth. Whereas, if planted directly outdoors, 6-8 hours of direct sunlight are necessary for root formation. Ensure you do not plant them with shade-loving plants like hostas, as that can make zinnia seedlings fight for basic sunlight and ultimately make them leggy.
2. Watering
The zinnia seedlings require consistent watering. 1 inch of water per week is considered ideal for the survival of the seedlings. Water them at the base for proper water absorption. Check the moisture levels of the soil before watering. Place a finger 2 inches deep in the soil, and if it’s dry, water the soil immediately. This prevents waterlogging and the chance of root rot.
3. Spacing and Thinning
Place the seedlings at least 6-12 inches apart for proper spacing and air circulation. This prevents overcrowding, helps distribute the natural resources adequately, and ensures the plant’s health. Another key care tip for zinnia seedlings is thinning. This process involves snipping off dead leaves as the seedling reaches 3 inches in height. It usually happens right before the plant is ready for transplantation to avoid any form of infection in the leaves.
Common Pests and Diseases That Affect Zinnia Seedlings
Damping-off disease, aphids, and slugs are major pests and diseases that are pretty common in zinnia seedlings. Since the plant is in its early stages, the roots are weak and are susceptible to many fungal diseases and pests.
Take a look at the table below to explore the pests and diseases in the zinnia seedlings:
Common Zinnia Seedling Problems With Their Solution
The most common problems while growing zinnia seedlings are leggy growth due to improper lighting, poor and delayed germination due to cold soil temperature, and damping off caused by weak cell walls. While these challenges are easily manageable, they are often overlooked due to a lack of care, which later reflects in the plant’s growth.
I have mentioned these common challenges with their direct solutions for an easier gardening experience:
1. Leggy Growth
Some young zinnia plants/seedlings often grow weak and leggy stems, which is caused primarily by improper lighting. When the plant has to struggle to find the required sunlight, it extends its stem and, in turn, becomes leggy.
Solution: If planted indoors, place the seedlings under grow lighting for at least 12-16 hours, and if they are directly sown outdoors or are transplanted outdoors, 6-8 hours of direct sun exposure is essential for root formation.
2. Poor Germination
Poor or delayed germination in zinnia seeds occurs when they are planted in cold soil or are not provided with adequate care after sowing. This results in delayed root formation, and the seedlings grow to be extremely weak or do not grow at all.
Solution: Zinnia seeds require warm temperatures to survive, so make sure the soil temperature is consistently between 21°C and 27°C. Cold soil will inhibit the process of germination. Water the soil well and make sure it has been provided with adequate light throughout the growing season.
3. Fungal Diseases and Pests
According to the University of Maine, damping off, which is a fungal disease, can cause the seedling stem to droop off into the soil. Young seedlings are susceptible to fungal diseases and pests due to soft tissues and soil-borne pathogens; therefore, accurate measures are essential for pest-free seedlings.
Solution: Discard the infected plant immediately before the infection spreads. Make sure the plants are spaced well with 6-12 inches of gap between them for proper air circulation.
YourHomify Insight
Zinnia seedlings are the most prone to pests and diseases as they have not yet formed strong cell walls. While insecticidal soaps are recommended to eradicate them, I would suggest manual discarding to eliminate the risk of leaf damage in young seedlings.
Concluding Remarks
Conclusively, zinnia seedlings are an important growth stage in growing these summer flowers. These newly emerged sets of leaves determine the health of the plant, as the plant is susceptible to major diseases due to weak cell walls. They can be grown indoors using grow lights and later transplanted outdoors when the danger of frost has passed.
My advice to beginners would be to wait till the danger of frost has passed and then plant the seedlings outdoors directly to remove the risk of transplant shock, which is new to novice gardeners.
Happy Gardening!
FAQs
Why are zinnias considered a dirty flower?
Zinnias are considered a dirty flower because their cut stems produce a white sap that can contaminate the water with bacteria in the vase.
What do zinnias look like when they first sprout?
Zinnia produces a set of two leaves when they sprout for the first time. Also known as cotyledons, they are oval-shaped, small green leaves that are not true leaves but are necessary for the formation of leaves until true leaves emerge after 1 week of sowing seeds.
How long does it take for zinnias to bloom from seedlings?
It takes almost 6-8 weeks for the zinnia seedlings to grow and produce flowers after they are transplanted outdoors. Flower buds appear after 3 weeks of planting if proper care is provided.
Can I scatter zinnia seeds from seed?
Yes, scattering zinnia seeds directly in the ground is a common practice to grow zinnia flowers. Make sure to rake the soil well and then cover it lightly with soil to ensure proper growth.
What should not be planted near zinnias?
Zinnias should not be planted near shade-loving plants like hostas, as zinnias require 6 hours of direct sunlight; aggressive spreaders like mint for proper spacing and growth; and powdery mildew targets like cucumber, to avoid pest infestations.
- Zinnia Diseases—Penn State Extension
- What’s Wrong With My Zinnia Seedlings? University of Maine
