Zinnias can be grown from seed that is sown early indoors and moved outside after a frost, or from potted plants or seeds sown directly in the ground after a frost.
Indoor Seed Sowing
- Utilizing a seed starting kit, sow indoors 5-7 weeks before to the date of outdoor planting in the spring.
- plant seeds A quarter-inch deep in seed starting solution
- At 70–75 degrees Fahrenheit, keep the soil moist.
- The seedlings appear in 7–10 days.
- As soon as seedlings appear, give them lots of light on a sunny windowsill or grow them 3–4 inches beneath 16–hour-per-day fluorescent plant lights that are off for eight hours at night. As the plants get taller, turn up the lights. Because they will become too hot, incandescent bulbs will not function in this process. Do not leave lights on continuously for 24 hours; most plants need a time of darkness to flourish.
- when they have two sets of leaves, thin to one seedling per cell.
- Seedlings don’t require a lot of fertilizer; feed them when they are 3–4 weeks old with a starter solution (half the strength of an indoor plant food), as directed by the manufacturer.
- After the first frost, transplant hardened-off seedlings into the garden.
- Seedling plants must be “hardened off” before being planted in the garden. By relocating young plants to a protected area outside for a week, you can acclimate them to outside circumstances. At first, be sure to shield them from the wind and the light. If frost is expected at night, cover or bring pots inside; then, in the morning, reintroduce them to the outdoors. The plant’s cell structure is toughened during the hardening off process, which also lessens transplant shock and scorching.
Direct Sowing in the Garden
- After any threat of frost has passed, direct-sow seeds in ordinary soil in full sunlight.
- The top 6 to 8 inches of soil should be cleared of weeds, and then it should be leveled and smoothed.
- The majority of plants do well in soils that have had organic matter added. Compost is a beautiful organic material that can be applied to your planting area whenever you like. It has the perfect pH level and nutrient balance. If compost is not available, topdress the soil with 1-2 inches of organic mulch after planting; this mulch will break down into compost over time. Following the growth season, a soil test will reveal what soil amendments are required.
- equally space the seeds 12 inches apart, then top with 1/4 inch of fine dirt.
- Lightly press the soil with your hand, water, and maintain an uniform moisture level.
- In 7–10 days, seedlings will start to show.
- When seedlings are 1-2 inches tall and 8–24 inches apart, depending on the variety, thin them.
- Choose an area with good, rich, moist organic soil that receives direct sun.
- Turn the soil under to a depth of 8 inches to prepare the bed. To get rid of grass and stone clumps, level the area using a rake.
- For each plant, create a hole that is sufficiently large to hold the root ball.
- Set the top of the root ball so that it is level with the dirt around it. Up to the top of the root ball, cover with soil. Your hand should firmly push the earth down, leaving a small depression to hold water around the plant.
- Water deeply until a puddle appears in the saucer you have made. As a result, there is strong root-to-soil contact and the plants become established.
- Use the plant tag to indicate its location.
How to Grow
- Keep weeds under control while the plants are growing. Weeds compete with plants for water, space, and nutrients, therefore keep them in check by frequently cultivating or by using a mulch to stop the germination of their seeds.
- Mulches also support stable soil temperatures and moisture retention. Shredded leaves used as an organic mulch for annual plants give the bed a more natural appearance and, as they decompose over time, enrich the soil. Mulches should never be placed on a plant’s stems to avoid potential decay.
- During the growing season, make sure plants are well-watered, especially during dry spells. The growing season requires roughly 1 inch of rain every week for plants. To determine whether you need to add water, use a rain gauge. The optimum irrigation method is a drip or trickling system that releases water at low pressure directly into the soil. To reduce disease issues, water early in the day if you want to use overhead sprinklers so the foliage has time to dry before dusk. Maintain a moist but not saturated soil.
- Some protection from strong winds and intense sunlight may be required until plants grow established. Additionally essential is good airflow.
- A mild fertilizer can be administered after new growth starts to show. To prevent burn damage, keep granular fertilizers away from the plant’s top and leaves. Use moderate amounts of a slow-release fertilizer because greater amounts could promote root rots.
- Unless you are growing them purely for cut flowers and want long stems, pinch young plants to induce branching.
- To prolong plant flowering till fall, remove spent flower heads. Cutting zinnias fosters the emergence of fresh blooms and they make excellent cut flowers.
- Observe for illnesses and pests. For advice on pest management measures that are suitable for your area, contact your cooperative extension service.
- In order to prevent disease problems the next year, remove plants that have been killed by frost in the fall.
- Zinnias can be arranged in tiny clusters alongside perennials or in mixed plantings with other summer annuals. They thrive in cottage and kid-friendly gardens, and cutting gardens frequently cultivate them.
- For containers, shorter zinnia cultivars are best. Be careful not to crowd them because the plants may grow taller and the blossoms may be much less than they should be. Never use garden soil instead of commercial potting mix, and make sure the containers have enough drainage. Plants growing in containers will need more water and fertilizer; keep an eye out for wilting or nutrient deficiencies.
- For cut flowers, trim stems before the blossom opens.
- Hummingbirds, butterflies, and beneficial insects are drawn to zinnias.
Common Disease Problems
Alternaria Leaf Spot: On the upper surface of the leaves and along the midrib, small, rounded, reddish-brown dots with white to gray centers appear. The lesions could surround the stems and result in wilt. Warm, rainy, or extremely humid conditions makes this sickness worse. Avoid getting water on the foliage, advises Burpee. Avoid working with moist plants and remove any contaminated plant components. Make sure there is lots of air movement. For advice on fungicides, get in touch with local cooperative extension service.
Aster Yellows: Plants grow excessively, become stunted, and develop witch’s brooms. Their petals also turn green and become malformed. Leafhoppers propagate this virus-like ailment. Burpee advises removing and destroying diseased plants. Eliminate leafhoppers. Eliminate any weeds in the area that the illness can also live on.
Bacterial Leaf Spot: The earliest symptoms are small, translucent spots with a wide, yellowish edge. Over time, these spots gradually get larger and develop an angular or irregularly circular shape with a reddish center. It flourishes in cooler climates. Flower heads may be impacted by the disease and become deformed. Burpee advises getting rid of diseased plants. Crop rotation should involve diverse family plants. Avoid watering from above. When plants are damp, stay away from them.
Botrytis: This fungus turns flowers, leaves, stalks, and buds a greyish color. It thrives in chilly, rainy weather. Burpee advises removing the damaged plant sections, avoiding watering at night, and not watering directly on the plant. Make sure plants receive adequate airflow. For advice on fungicides, get in touch with local cooperative extension service.
When the weather is humid, a fungus illness known as powdery mildew develops on the tops of the leaves. The surface of the leaves seems to be white or grayish, and they may curl. Burpee advises giving the plants adequate air circulation through optimum spacing and pruning in order to prevent powdery mildew. For advice on fungicides, get in touch with local cooperative extension service.
Common Pest and Cultural Problems
Aphids: These disease-transmitting sucking insects that feed on the undersides of leaves might be green, red, black, or peach in appearance. On the foliage, they deposit a sticky substance that draws ants. Burpee advises attracting or introducing aphid-eating predators like lady beetles and wasps into your garden. You can also use an insecticidal soap or a powerful spray to wash them away.
Leafhoppers: These insects damage leaves and retard growth. Moreover, they spread sickness. Burpee advises clearing up plant detritus. Use soaps with insecticides. For additional advice on insecticides, contact local cooperative extension service.
Burpee advises hand-picking Japanese beetles in the morning into a pail of soapy water.
Compared to what is typical for the variety, plants are shorter, and blossoms are much smaller: Overcrowding can cause zinnias to become stunted and produce smaller flowers. Always adhere to the spacing guidelines for each variety.
Spider mites: These minuscule insects, which resemble spiders, are approximately the size of a peppercorn. They can be yellow, brown, black, red, or black. They ingest plant liquids, sucking out chlorophyll and injecting poisons that leave the foliage with white spots. On the plant, webbing is frequently seen. They cause the leaf to stipple, dry, and become yellow. They proliferate swiftly and do best in dry environments. Burpee’s Advice Every other day, a strong spray can help control spider mites. Try using insecticidal soap or hot pepper wax. For advice on miticides, contact your local Cooperative Extension Service.
Is it better to start my zinnias outside or inside? You can either start zinnias inside or outside, in the garden. You can get a head start by beginning them indoors if you have suitable indoor growth conditions, such as plant lights and a heat mat for germination. However, because zinnias are simple to grow from seed and bloom quickly, some gardeners may find that direct sowing is a superior alternative.
Is it possible to cultivate zinnias indoors? Zinnias may not thrive in many homes since they need full sun and high temperatures to develop effectively. In the summer, shorter varieties can be tested in a warm sunroom.
How should I take care of the cut zinnia flowers? When you cut your flowers in the garden, bring a pail of water with you, and as soon as you cut the flowers, immediately submerge them in the water. They will be able to absorb water through the newly sliced stem as a result. More surface area for the water to absorb when cut at an angle. Keep them away from the sun’s rays.
Do my zinnias need to be staked? Staking may be beneficial for taller kinds, especially if they are in a windy environment.
Why do my zinnias have much less flowers than I imagined and are tall and lean? Zinnias will grow tall plants and much smaller flowers if they are planted too near together. Always adhere to the planting instructions’ suggested spacing.
How can you encourage the growth of zinnias?
It’s crucial to clip your zinnia blooms as they appear to ensure that they continue to grow and bloom. 12 Zinnia plants were planted by me at the start of the summer. I probably cut more than 200 to 300 zinnia blossoms from these bushes over the course of the summer. It was great to watch them develop further!
Here are a few recommendations for flower cutting:
- Make sure the bloom is prepared to be cut by inspecting the stem. Take hold of the stem above the intended cutting point and shake the flower a little. Give the stem a few more days if it feels flimsy; it has to be strong and devoid of any give.
- To cut, cut just above the leaves as seen in the image above, following the stem as closely as you can to the main stem of the plant or where it joins another stem.
How can I grow zinnias that are fuller?
Consider pinching to be a type of pruning. Like all plant pruning, it is carried out in a certain way to achieve a particular goal.
Pinning zinnias stimulates the plant to grow additional stems, which gives the plant a fuller appearance and more blooms.
For many gardeners, pinching zinnias is a routine operation because they are so responsive to it and nearly always send out new stems.
Is Pinching Necessary?
It is entirely optional, though. In order to observe what new growth develops and how many flowers I can acquire, I truly like continuing to pinch.
However, you might not want to if you’re growing for conventional cut flowers. Instead, if you want the arrangement to stand up well in a vase, you can pick a robust, single main stem with one stunning flower on top. The flowers on branches often have a reduced bloom size compared to those on the main stem. Still stunning, just scaled down.
What causes the slow growth of my zinnias?
Sun. Zinnia blooms take a significant amount of energy from the plant. As a result, zinnias need at least six hours of direct sunlight each day to grow well. Long periods of insufficient sunlight will prevent fresh zinnia seedlings from growing.
Do zinnias grow larger?
Simply direct sow the seeds in a sunny area after the last frost if you decide to plant zinnia seeds outside. A few inches of mulch or compost along with some fertilizer should be added, suggests Kristin Winterbottom of Parkseed (opens in new tab).
Planting zinnias too soon is one of the most typical gardening errors. Only plant your zinnia seeds after all danger of frost has passed and the chilly nights have subsided since they won’t survive any frost.
Zinnias prefer some space to stretch out and will grow taller with richer soil. Rake over the bed to get it ready, then check the seed packet for proper spacing before adding a thin layer of soil. Carefully space the seedlings at 15 inches (40 cm) intervals as they mature.
“Water at the base of the plants to keep the soil moist. Kristin continues, “Cut blossoms frequently for arrangements or just pinch off spent blooms.”
Taller types will flower better if you stake them with canes or twig supports.
Alternatively, you can plant zinnias when they are still little and have only one or two genuine leaves by sowing them in modules or seed trays, which prevents pricking out. Sarah Raven advises minimizing root handling in this manner.
The answer to the question “should I soak zinnia seeds before planting?” is yes. Your seeds will grow more quickly if you soak them. The seed will begin to rot if it is left in water for too long, so you must be careful. Your seed should soak for 8 to 12 hours.
If you’re pressed for time or want to grow zinnias quickly, consider purchasing plug plants and starting them in individual pots before transplanting them outside.