Few flowers can bring a dramatic, long-lasting impact like zinnias. These gorgeous annuals are available in beautiful pastel colors such as pink, purple, orange, or yellow. To produce stunning flowers and keep their stems nice and robust, zinnias need the correct amount of water. In this article, we’ll run through everything you need to know about when and how to water Zinnia flowers in your garden.
When and How to Water Zinnias – The Essentials
Zinnias need to be watered once per week or whenever the top inch or two of soil is dry. Although zinnias are drought-tolerant, they still need plenty of water to produce their famous flowers. In excessively hot temperatures, zinnias may even need watering once a day. Water zinnias in the morning whenever possible and avoid overwatering zinnias to prevent diseases or pests.
About Zinnias
Family & Genus
The Zinnia genus is part of the Heliantheae, or sunflower tribe of the daisy family (Asteraceae). The genus contains 22 recognized species and is named after the 18th Century German botanist Johann Gottfried Zinn. Common species like Zinnia elegans and Zinnia angustifolia have been used to create several different types of zinnia cultivars.
Botanical Characteristics
Zinnias come in single, double, or semi-double forms with composite flower heads. The disc of central florets is surrounded by rays or banks of petals. These petals come in various colors, including pink, purple, orange, red, green, and white. The flowering season runs from early summer until the frosts arrive in fall, and they make lovely cut flowers for vases or bouquet arrangements.
Zinnias are flowering annuals that only last for a year and typically form clumps. Some zinnia species may grow as flowering shrubs or sub-shrubs. Zinnias usually grow between 1 and 4 feet tall. You can also get compact varieties ranging from 6 to 12 inches tall.
Zinnias are also non-toxic for humans and pets, so you can safely grow them if you have cats or dogs.
Native Range
Originally native to Mexico, zinnias can be found in parts of Central and South America and the Southwestern United States. Zinnias prefer arid, warm, sunny habitats such as dry grasslands, prairies, and shrublands. As drought-tolerant plants, zinnias are well-suited to growing in these areas.
Care & Maintenance
Zinnias are wonderfully easy plants to grow, especially for novice gardeners. Zinnias need full sun for at least 6 to 8 hours daily in a warm, sheltered spot. These flowers like fertile, well-draining soils such as chalk, clay, loam, or sand. Zinnias should be deadheaded during the flowering season and fertilized once every one or two weeks for the best flowers.
Meaning & Symbolism
Zinnias symbolize romantic love and affection for friends as well as celebration and reunion. Victorian flower language strongly associates zinnias with friendship. Zinnias were used to convey the fact that you were thinking of absent friends.
The Importance of Watering Correctly
Like almost every other inhabitant of the Earth, plants need water to survive. Studies have shown that approximately 95% of a plant’s mass is comprised of water in the form of plant tissue. Plants need water to create new tissue, enabling them to grow and flower.
Using their roots, plants absorb water and nutrients from the ground to create the essential building blocks of growth. During photosynthesis, water is mixed with carbon dioxide to produce glucose. This vital sugar is the primary fuel source for plant growth and helps manufacture cellulose, which is turned into tissue.
Plants absorb nutrients from the soil when taking up water through their roots. This is the only way that plants can get nutrients like potassium and phosphorus. Plants use these nutrients to produce new leaves and, especially in the case of zinnias, big beautiful flowers.
Water also enables plants to avoid overheating in high temperatures. Using the large surface provided by its leaves, a plant can get rid of excess water through evaporation. This process forces the roots to draw more water up from the soil to keep the plant healthy.
When to Water Zinnias
Zinnias typically need to be watered about once per week or whenever the top inch or two of soil is dry. Although zinnias are drought-tolerant, they still need plenty of water to produce their famous flowers. In excessively hot temperatures, zinnias may even need watering once a day.
Water is vital for young zinnia plants that may have just been transplanted outside. Young zinnias should be watered a few times a week with about an inch of water each time. Zinnia seedlings should also be watered every two or three days to fuel their growth.
It’s best to water zinnias when temperatures are lower in the morning, wherever possible. If you water zinnias on a hot afternoon, most of the water could evaporate before reaching roots. Watering in the morning means more consistent evaporation, which helps avoid leaving the zinnia in wet soil overnight. In colder areas, soil that is still wet at night increases the risk of diseases or pests.
Do Zinnias Prefer Moist or Dry Soil?
Zinnias need slightly moist, well-draining soil rather than dry soil, even though they’re drought-tolerant plants. Zinnias should be watered whenever the top couple of inches of soil feel dry. This keeps the soil moist enough without the risk of overwatering.
Moist soil is essential for seedlings and younger plants. If zinnias are left to dry out too much in these crucial stages, their growth will be hampered. Young zinnias may need watering up to three times a week.
Seasonal Changes to Consider
It’s important to consider seasonal changes when watering zinnias, especially concerning temperature. Zinnias grow as annuals in USDA Zones 2 to 11 and will be fine in most climates if they receive average rainfall.
In extreme heat or extended periods of drought, zinnias need to be watered more frequently. Sometimes, zinnias need watering once a day to help them survive the heat. Zinnias are not hardy annuals and will die back as soon as the first frosts arrive in the fall. You won’t need to water them at all in the winter.
How to Water Zinnias
Whenever you water zinnias, give them a good, deep watering when the top two inches of soil feel dry. Aim your watering can at the base of the stems to avoid getting water on the leaves or flowers. If you water from above, the soggy leaves and flowers will be easy prey for pests and diseases.
Water your zinnias in the morning to give excess water plenty of time to evaporate throughout the day. Watering zinnias in the evening can lead to problems, especially in colder areas. The plant is at risk of diseases or pests if the soil is still wet overnight.
Signs of Overwatering
Although zinnias need plenty of water to produce flowers, they can suffer from overwatering. Here are the main symptoms of overwatering:
Drooping or yellowing leaves
If zinnias sit for too long in waterlogged soil, the leaves may start drooping or turning yellow. These symptoms may also indicate diseases that are caused by overwatering. Check to see if the soil feels soggy and allow the plant to dry out a bit before watering.
Root rot
Root rot is a common problem for overwatered plants. If your zinnias look unhealthy, it’s worth checking the roots. If the roots are brown, mushy, and smelly, the plant is suffering from root rot. Trim away the affected roots and leave the zinnia to dry out before watering again.
Signs of disease
Diseases like powdery mildew and leaf spot are more likely to occur if a zinnia is overwatered. If you see signs of these diseases, check the soil. If it feels damp or soggy, you’re overwatering the plant. Allow it to dry out and remove affected foliage.
Signs of Underwatering
Zinnias can also be vulnerable to underwatering, especially in hot, dry conditions. Here are the main symptoms of underwatered zinnias:
Cracked, dry soil
This is a clear sign of underwatering. Dry soil with be cracked and will feel hard to the touch. This makes it harder for water to soak through to the roots. Water little and often until the soil returns to normal.
Wilting, yellowing, or shriveled leaves
Zinnias that aren’t being watered enough will have wilting, yellowing, or shriveled leaves. Check the soil to see if it feels hard or dry. Then water the plant more frequently, and the leaves should perk up reasonably quickly.
Floppy or weak flower growth
Zinnias depend on water to produce large, showy flowers. If the flowers look small or droopy, the plant may not be getting enough water.
Watering Zinnias FAQs:
What are the common signs that a zinnia needs watering?
Zinnias with yellowing, wilting, or shriveled leaves and dry, cracked soil need watering.
Should I avoid the leaves when watering zinnias?
Always avoid the leaves and flowers when watering zinnias. Aim your watering can at the base of the stems. Wet foliage can be afflicted by pests or diseases.
What should I do if I overwater my zinnias?
If you think your zinnias are overwatered, check the soil. If it feels damp, let the top two inches of soil dry out before watering again.
Wrapping Up
Zinnias are brilliant flowers for any garden because they’re low-maintenance and produce bold, colorful blooms. One of the primary considerations when cultivating zinnias is giving them the right amount of water. Established zinnias should be watered about once a week, while seedlings or young plants need watering every few days. Water more frequently in hot temperatures and in the morning whenever possible.
For more, see our in-depth guide on how to grow zinnias in pots and containers.
Edd is a budding content writer and gardener living in the United Kingdom. He has a bachelor's degree in Creative and Professional Writing and has written for several gardening publications online. He is passionate about nature and sustainability with a focus on gardening and wildlife.
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