Zinnias: planting, location & care tips

Regina
Regina
Regina
Regina

I studied horticultural sciences at university and in my free time you can find me in my own patch of land, growing anything with roots. I am particularly passionate about self-sufficiency and seasonal food.

Favourite fruit: quince, cornelian cherry and blueberries
Favourite vegetables: peas, tomatoes and garlic

Zinnias have always been popular summer flowers, and with their variety of colours and abundant flowering, they are a joy for any gardener. We introduce the zinnia and give tips for cultivation in your own garden.

Zinnia
Zinnias come in every colour imaginable, with double and single flowers [Photo: Joko P/ Shutterstock.com]

The zinnia is a summer flower found in almost every cottage garden (Zinnia elegans). It is sometimes popular as a cut flower, as it produces numerous colourful flowers throughout the summer. In this article you will learn everything about the zinnia, its characteristics, requirements for location and care, as well as details about sowing and planting.

Zinnia: origin and characteristics

Zinnia belongs to the large daisy family (Asteraceae) – just like the common daisy (Bellis perennis) and dahlias (Dahlia). There are about 20 species in the genus Zinnia, which grow as annuals, perennials or as half-shrubs. The main variety planted here is Zinnia elegans. This annual summer flower is originally from Mexico and is also found in other areas of Central and South America. The zinnia was named by the famous Swedish botanist Carl Linnaeus in honour of the Göttingen anatomist and botanist Johann Gottfried Zinn.

Zinnia is an annual summer flower that grows upright and bushy. The leaves of the zinnia are characteristically heavily covered with short hairs, making them feel rough. They sit directly opposite on the flower stalk and are roughly triangular in shape. A terminal flower forms at the end of each stem and, depending on the variety, can be double or single and coloured in many shades from white to yellow, orange, red and dark pink. However, strong colours fade quite quickly in strong sunlight. The flowering period of zinnias extends from July to September, occasionally into October.

Tip: Zinnias are bee-friendly ornamental flowers because they provide nectar to eager pollinators such as bees, bumblebees and butterflies. The zinnia flower makes up for the relatively small amount of sugary juice per flower with its high flowering rate.

Bee on pink zinnia flower
Zinnias attract honey bees, wild bees, butterflies and many other insects

The most beautiful species and varieties

If you want to plant zinnias, there is a huge selection of varieties and also a few different species of the genus Zinnia. They differ mainly in flower colour, shape and size, as well as the height of growth. While you can also use tall-growing cultivars for bedding, small-growing dwarf zinnias are better suited for the balcony. We present a selection of the most beautiful varieties of zinnias for all locations.

All varieties mentioned belong to the species Zinnia elegans.

  • ˈLiliputˈ: Low-growing zinnia mixture of various coloured, small-growing plants with a growth height of only 50 – 60 cm. The flowering period extends from July to October.
  • ˈPeter Panˈ: Dwarf zinnia with only 30 cm height of growth and about 8 cm flowers in orange-yellow to blood-red colour.
  • ˈPolar Bearˈ: Almost entirely double white zinnia with large flowers and plants up to one meter high.
  • ˈGiant Cactusˈ: 60 – 80 cm tall zinnia variety with semi-double, large flowers and slightly rolled petals reminiscent of cactus dahlias.
  • ˈThumbelinaˈ: Smallest of all low zinnia varieties with only 15 – 20 cm growth height and dahlia-like flowers in a wide range of colours. Ideal mini zinnia for small balcony boxes and pots.
  • ˈWhirlygigˈ: Colourful mix of two-tone zinnias that have various combinations of pink, orange, red and white and about 60 – 70 cm growth height.
  • Zinnia angustifolia: Narrow-leaved zinnia with lavender-like leaves and small red, pink, deep orange, yellow or white flowers. The petite plants reach a height of growth of about 30-50 cm.
Many orange zinnias
Low-growing, narrow-leaved zinnias produce small, simple flowers and pointed leaves [Photo: yuthapong kaewboon/ Shutterstock.com]

Growing zinnias

Zinnias are extremely rewarding flowering plants, if you pay attention to their needs in terms of location, sowing and planting. We provide important tips for successful cultivation and planting zinnia.

The right time for planting zinnias

Zinnias are freshly sown as annual ornamental plants every year and planted out only after the last frost in mid-May. Growing is in March on a warm windowsill, but it is possible to buy seedlings and plant them after the Ice Saints.

The right location

The ideal location for zinnias is basically sunny, protected from the wind and warm. The ornamental plant prefers to thrive in loamy, sandy, nutrient-rich soil that retains moisture well but never becomes waterlogged. Whether in the garden, in a pot or on the balcony, zinnias thrive outdoors as well as in a container, as long as the location and care are right. However, the pretty summer bloomers require rotation. Therefore, every year should the location or planting soil should be changed.

Yellow, pink and orange flowering zinnia
Zinnias need a warm, sunny location to thrive [Photo: Zhou Eka/ Shutterstock.com]

Tip: Zinnias do not tolerate heavy rain, this can damage the flowers, and the tall-growing varieties in particular can fall over. A rain-protected location is therefore important.

Sowing, pricking out and planting zinnias

Zinnias can be started indoors between February and April, because their seedlings also do not tolerate cold and love the warmth. To sow zinnias, first prepare a growing tray or small pots and fill them with a low-nutrient growing soil such as our Plantura Organic Herb & Seedling Compost. During and in the period immediately after germination, seedlings of zinnia require very few nutrients and are encouraged by a nutrient-poor soil to form strong roots. Now sow the zinnia seeds with a depth of about 0.5 to 1 cm in the soil, water and place the seed tray or pot at 16 to 20 °C on a bright windowsill. Always keep the soil well moist, but not wet. Germination occurs after about 10-20 days. As soon as the first true leaves form after the cotyledons, you can prick them out. Now transplant the seedlings into more nutrient-rich soil in individual pots and allow the zinnias to continue growing at slightly cooler temperatures of 12 to 15 °C until planting.

Zinnia seedlings
Zinnia seedlings should not be planted outside until around mid-May [Photo: Irina Kvyatkovskaya/ Shutterstock.com]

After the last frost, the young plants may be placed outdoors in mid-May to late June. Whether in a pot, balcony box or bed, leave 20 to 30 cm of planting space between each zinnia. Bushy growth of zinnia usually closes the gaps quite quickly. For planting on the terrace and balcony, choose planters with good water drainage and sufficient size. For individual zinnias, the pot should hold at least 5-10 litres, depending on the strength of growth. Fill the bottom of your planters with a drainage layer of coarse gravel or expanded clay about 3 inches high and top it off with a nutrient-rich potting soil, such as our Plantura Organic Flower Compost. Sustainably produced potting soil contains all the essential nutrients to promote lush blooms and plant health. Now place the zinnia seedlings in the soil, observing the planting distance. After that, you need to water vigorously, so that the soil is flushed to the roots and zinnias can grow well.

Summary: Planting zinnias

  • Sow: February – April
  • Germination: after 10 – 20 days
  • Plant out: mid-May – late June
  • Planting distance: 20 – 30 cm
  • Location: Sunny, warm, sheltered from wind
  • Soil: Loamy, sandy and nutrient-rich
  • Cultivation possible in beds or containers

Zinnia care

Zinnias are thirsty garden inhabitants and require a regular water supply. The soil should always be kept evenly moist for them, but should never get wet or waterlogged, otherwise root rot may occur. Magnificent flowering zinnias can be cut throughout the flowering period for the vase. To do this, use a sharp knife and cut the flower stalk back to one pair of leaves at a time, because this is where the plant will re-branch and form flowers again. The flowers keep fresh in the water for about one to two weeks.

Pink zinnias in glass jars
Zinnias also look good as cut flowers in vases [Photo: Sarycheva Olesia/ Shutterstock.com]

Faded zinnia flowers should also be removed periodically to maintain bloom – unless seeds are to be obtained.

Zinnias, like many summer flowers, depend on a regular supply of nutrients and should therefore be well fertilised. When fertilising zinnias in pots or balcony boxes, we particularly recommend using a liquid nutrient fertiliser such as our Plantura Liquid Flower Food. About every two weeks, 15 to 25 ml is added to 5 litres of irrigation water and thus simply applied when watering. The nutrients contained reach the roots directly and are quickly absorbed. Acute deficiency symptoms, such as a yellowing of the lowest leaves due to nitrogen deficiency, can also be quickly remedied in this way.

Plantura Liquid Flower Food
Plantura Liquid Flower Food

Liquid fertiliser with an NK ratio of 3-4, for all flowering plants, promotes healthy plant growth, child & pet friendly

Are zinnias hardy?

Zinnias are not hardy in this part of the world, because they do not tolerate frost of any kind. As is usual with annual plants anyway, zinnias die off completely after the seeds have matured, so it can’t be overwintered indoors either. The plant only survives to the following year in the form of seeds.

Zinnia propagation

Zinnias can be propagated by their seeds. However, in order for seeds to form, they must not be double flowered, as they are infertile. Flowers visited by bees and other pollinators cross with other zinnia varieties, so that often the seed no longer contains the original variety of the mother plant. However, for those for whom varietal purity is not a top priority, they may enjoy gorgeous new colour combinations from home-grown seeds. For seed collection, faded flowers must of course be left and not cut. The numerous elongated achene fruits of the zinnia ripen until October and can be cut off together with the flower head in late autumn, when the inflorescence has dried up, then dried indoors at room temperature for two to three weeks. As soon as the seeds trickle out on their own after a little rubbing, separate them from flower remnants and store them in paper bags in a dry, cool place. Zinnia seeds can germinate for about four years if stored well.

Zinnias seeds and petals
Once dried, the brown seeds can be separated from the petals [Photo: Tongsai/ Shutterstock.com]

Common pests

Slugs love zinnias and can quickly kill young plants completely. Adult zinnia plants, on the other hand, are rarely at risk.

So snail protection makes sense especially in the first weeks after planting. In addition, leaf aphids and spider mites will swarm on the summer bloomers when the time comes. However, outdoors, beneficial insects such as the ladybird quickly limit explosive reproduction.

Are zinnias poisonous?

Zinnias are not poisonous per se, but they can cause allergic reactions when the sap comes into contact with the skin. This is due to alkaloids such as nicotine and various terpenes contained in it. You should therefore always wear gloves when cutting zinnia. The flowers of the zinnia, on the other hand, are edible and also offer a real feast for the eyes as a decoration or ingredient in flower butter.

A distant relative of the zinnia is the annua sunflower which can grow to amazing heights. We introduce you to the popular summer flower and cover all topics from variety selection to planting and care to harvesting.

Plantura's Garden-Mail Newsletter