Dahlia Vs Zinnia (Differences, Similarities & Growing Guide 2023)

Dahlia and zinnia are both flowers that look very similar to each other. If you’re not paying attention, you might not notice any difference between these flowers at all. However, if you want to learn more about the differences between dahlias and zinnias, keep reading.

With a bit of research and knowledge, you’ll soon be able to tell a dahlia apart from a zinnia with ease.

Dahlia vs Zinnia

While both dahlia and zinnia look alike, one of the main differences between both flowers is in their lifespan and the way they reproduce. Like most flowers, zinnias grow from their seeds whereas dahlias usually grow through tubers that make it easy to replant them.

In the language of flowers, dahlias represent beauty, commitment, kindness, and steadfastness. While zinnias represent remembrance of absent friends. There are a lot more differences and similarities between these plants so let’s go over them.

Comparison

	Dahlia	Zinnia
Leaf Color	Deep shade of green	Pale to Medium shade of green
Stem Color	Green, Purple or Tan	Green or Tan
Variegation	Has 42 different species	Has 20 different species
Flower	Has 14 different colored flowers	Has 5 different colored flowers

Other similar comparisons:

• Philodendron Black Cardinal vs. Rojo Congo
• Sansevieria Fernwood vs. Cylindrica
• Yucca vs. Dracaena

Dahlia vs Zinnia Differences

Apart from the differences we mentioned above, these plants are also different in many other ways such as their physical appearances, environmental conditions, and external factors that help them grow.

1. Origin and Name

The zinnia flowers were named after the German botanist Johann Gottfried Zinn who found these flowers first in Mexico and brought them back to Europe to study. The zinnias have several different types but the most common one is the zinnia elegans. Zinnias are native to Mexico, and South and North America.

Dahlias or also known as dahlia hortensis are native to Mexico and South America as well but they are also native to Central America. They were given the name ‘Dahlia’ by the Spanish botanist Antonio Jose Cavanilles in the honor of Swedish botanist Anders Dahl.

2. Taxonomy

Just as their looks are similar, both zinnia and dahlia came from the same plant family, they share the same taxonomic subfamily of Asteriodeae in the Asteraceae family. This family is also called the daisy family.

However, zinnia and dahlias are two different genera with many subspecies in each genus. The most common zinnia is the zinnia elegans species whereas the common dahlia is the dahlia pinnata.

3. Shape & Appearance

Zinnia flowers typically have a dome shape to them whereas dahlias have more flat with a slight ball-like shape. Generally, the zinnia flowers are smaller than the dahlia flowers. However, this can change depending on the species of dahlia since there are also some species of dahlia with very small flowers.

4. Differences in Color

Both flowers have an array of colors. Zinnias can come in red, bronze, pink, orange, green, purple, yellow, white, lavender, and cream whereas dahlias usually come in white, purple, yellow, red, pink and some species even have two different colors in one flower.

5. Leaf Size and Texture

Aside from the colors, the leaves of both plants are very different. Dahlias have ovate-shaped leaves that are arranged opposite to each other. Zinnia leaves are also arranged opposite to each other but they overlap with each other at their base.

6. Height and Growth Rate

Dahlias are generally taller than zinnia plants. Zinnias can grow to the height of 50 inches in about 2 months whereas Dahlias can reach a maximum height of 60 inches over 12-16 weeks of growth. Zinnias can mature faster than dahlias making them easy to grow and use as decorations.

7. Flowers

Both dahlias and zinnias also come in multiple bloom types with dahlias having around 14 different types of bloom that are differentiated according to their disks, some dahlias have a central disk while others don’t.

Zinnia has five different varieties of flowers and every zinnia flower has a central disk. Zinnia flowers are smaller than dahlias in size however some dahlia species can be smaller than zinnia.

8. Growing Conditions, Temperature and Climate

Zinnias are more frost-hardy and can be grown easily even in cold places. Dahlias on the other hand can’t tolerate much frost. Zinnias ideally need daytime temperatures above 70°F, below 60°F their growth slows down. However, some species of zinnia can tolerate much lower temperatures.

Dahlias on the other hand are more temperature sensitive; they prefer cooler climates with daytime temperatures not above 80°F. However, temperatures below 60°F also negatively affect them. You can grow zinnias in USDA zone 3-10 whereas dahlias can only be grown in USDA zones 8-10.

9. Light, Water, Soil

Dahlias can grow in shady areas and containers with indirect sunlight. However, they prefer 6-8 hours of direct sunlight every day. Keep in mind that they are sensitive to hot weather so it’s better to give them indirect sunlight during midday when the sun is especially hot.

Zinnias are similar plants that need direct sunlight however, unlike dahlias, they do not mind hot temperatures and can tolerate direct sunlight even on very hot days.

Zinnias are also very drought tolerant and usually do not need to be watered. On the other hand, dahlias need to be watered 1-2 times per week depending on how hot it is.

Zinnias can be planted in any soil as long as there is enough space for their roots to spread, they do not have a pH preference but having a neutral soil pH can help them grow better. Dahlias prefer a slightly acidic soil pH of 6.5 with soft loamy soil rich in nutrients.

Dahlia vs Zinnia Similarities

Despite their differences, dahlias and zinnias are similar in their environmental preferences. Both plants love direct sunlight and have similar ideal temperature ranges. Here are some other ways these plants are similar.

1. Sunlight

Both dahlia and zinnia prefer direct sunlight for the best growth. Ideally, you want to give them 6-8 hours of sunlight every day. Still, you can place them under shade during especially hot days to avoid damaging the plants.

2. Watering

Zinnias are drought resistant and can be grown without needing to be watered much whereas dahlias prefer to be deeply watered every week. Still, both plants thrive when you deeply water them every week. Zinnias are prone to overwatering so only water them when the soil is completely dry.

3. Humidity & Temperature

The ideal range to grow both plants is between 70°F-72°F, even though they have different tolerances, neither plant can survive the winter frost so you need to wait for spring before you begin to plant them.

Zinnias and dahlias don’t like humidity. Ideally, you want to grow them in a low-humidity environment. Still, Zinnias can thrive at moderate to high humidity levels but too much humidity can stunt their growth.

4. Potting and Soil

Both plants prefer well-drained soil with plenty of organic nutrients. Zinnias prefer to have a lot of room to spread their roots. Dahlias and zinnias thrive in a neutral or slightly acidic soil pH. You can grow both plants in pots as long as the pot has enough room for the roots.

5. Fertilizer

A balanced fertilizer will help both plants thrive and bloom. Zinnias don’t need much fertilizer but dahlias are very hungry and will absorb as much fertilizer as you give them.

Too much nitrogen can increase dahlia foliage but lead to fewer flowers. Both flowers can use extra phosphorus and potassium. Dahlias prefer an NPK ratio of 5-5-10 whereas zinnias need a 10-10-10 ratio.

6. Natural Habitat

Both flowers originate and grow in Mexico and parts of America with similar climates. However, zinnias are believed to be introduced back in 1613, in Europe. Dahlias on the other hand is said to be first cultivated by the Aztecs.

Common Problems for Both Plants

Dahlias and zinnias are very different plants but both plants are vulnerable to similar problems since they both belong to the same botanical family. Here are some of the common problems for both dahlias and Zinnias.

Bacterial Disease

There are two kinds of bacterial diseases, bacterial wit, and soft rot, which affect Dahlias. As for zinnias, the most common bacterial disease is bacterial leaf spot.

While there are different signs for each bacterial disease, each bacterial disease will turn the flower brown and might even infect the other plants in your garden.

To prevent these diseases, isolate the infected plant and ensure you don’t use infected seeds to grow the plants. You can also use antibacterial sprays to help the plant resist diseases.

Aster Yellows

Aster yellow is a disease caused by the phytoplasma bacterium that thrives in other weeds or insects. The most common symptom is when the flowers and leaves turned into yellow color.

Though it is usually not lethal, it can slow down the growth of your plants. To prevent aster yellows, remove all overwintering weeds near your plant that might carry the disease. You should also use insecticides to prevent infected insects from transmitting the disease to your plants.

Infestation of Insects and Mites

Dahlias and zinnias are vulnerable to mite infestation. Some common pests like spider mites and aphids are prone to infest both flowers. These insects will eat your plant’s leaves and inhibit its growth. It is recommended to habitually use insecticides to prevent such infestations.

Outro

Overall, both Dahlias and zinnias come from the same plant family and even origin so they have some similarities. However, despite their similarities, they are very different plants that each has its charm. If you want a beautiful flower, dahlia is the best for you but if you want a hardy flower, zinnias will be your best friend.

Frequently Asked Questions