Select Page

Growing The Zinnia Flower

Beautify Your Garden with Hot Palette Blooms!

by Frances Santos

Growing Zinnias - The Zinnia FlowerWhether you’re a newbie or a seasoned gardener, you’ll definitely find it easy growing zinnias. And if you haven’t grown them before, put them on top of your to-do spring list this season.

Zinnia flowers are a wondrous gift from Mexico. They display cheery, deeply-colored blooms in vibrant hues of red, purple, pink, yellow and orange. The pink and red varieties are attractive to butterflies, which are a perfect choice for flower borders and flower pots. Zinnias also make good cut flowers with a vase life of 5 to 7 days.

Another reason why you should grow zinnias is because they are not poisonous and are absolutely safe for home gardens frequented by little kids and pets. But although they are not toxic, they are not a culinary flower.

Zinnia Flower Propagation

Zinnias can be propagated by cuttings. Bedding plants are also available but since it’s not at all difficult to propagate zinnias from seeds, why not grow them from seeds?

How To Grow Zinnias

Zinnias are not fussy, and growing zinnias is rather easy. Initiate planting them, stand back and you can just watch them grow into lovely blooms excellent for cutting. Choose a location with access to full sun. These lovely blooms need at least 6 hours of sun a day.

Soil Preparation

Breaking up the soil in your planting area with a potato rake before sowing the seeds is recommended. Zinnias can grow in average soils but it is best to condition the soil first. Soil conditioning can be done by adding some compost or by combining it with potting soil. Spread some sifted compost and scatter thinly over the planting area. Zinnias love moist soil with good drainage.

Sowing Seeds Indoors

Seeds can be planted indoors 6-8 weeks before the last frost and the seedlings can be easily transplanted into your outdoor garden later on. Remember that germination is less successful in cold soil. Moreover, it is best to soak dried seeds in water for 4-6 hours before planting.

Lay the seeds on a flat/shallow dish and cover them lightly with moist soil or vermiculate. The germination medium must be sterile and well-drained. The ideal pH is 6.0 to 6.5. Additionally, do not apply any surfactant to the germination medium as this may reduce plant’s vitality. Place the flat in a dark room. Take note that seeds need darkness and not light to germinate.

The germination process takes about 5-7 days at 75 degrees F. Remember, always keep the soil temperatures at above 60 degrees F, ideally at greater than 70 degrees F to prevent poor growth and tendency to become chloratic.

Sowing Seeds Outdoors

However, if you prefer planting the seeds directly in your flower garden, then so be it. Just make sure to start setting the seeds after the last frost date so the soil has warmed and can be worked. Typically, seeds are sown directly in the field/outdoors in May.

Transplanting Young Zinnia Plants

As the seeds start to sprout, encourage the stronger ones to grow by weeding out weak plants. Repot the seedlings to separate pots when they grow their first leaves. When planted in the field, space each row 12 inches apart, and within the row, spacing among the plants must be 6 inches apart. The estimated period from seeding to initial harvest is 6 to 7 weeks, provided that 70 degrees F soil temperature is consistently followed.


Add 2-3 inches of mulch once your plants have reached the height of 6-8 inches. Spread the mulch around the base using your hands. Make sure not to broadcast the mulch as this will injure tender shoots.

Periodic Fertilizing

  • Compost: Pull back the mulch every 6-8 weeks and add a thin layer of compost. In order to prevent moisture from evaporating out of the compost, return the layer of mulch over it.
  • Commercial Fertilizer: Determine the accurate nutrient content of your planting area by performing a soil test before starting any fertilizer program. Generally, it is adequate to use 1.5 to 2 pounds of nitrogen for every 1,000 sq. feet of bed space per year from a 1-1-1 fertilizer formulation. Now, in case the soil test results specify sufficient phosphorous and potassium content, you may use ammonium nitrate instead of a complete fertilizer (which contains nitrogen, phosphorous and potassium). Feed the plants with a portion of fertilizer when sowing and another portion in late July. The final application can be done in the first day of August.

Soils with low boron content can cause bud blasting and sluggish growth of branches. Conversely, excessive amounts of boron in the soil may slow down flowering 12 to 15 days. Zinnias must be given higher supply of nitrogen if they are grown as cut flowers, as compared to ones grown merely as a delightful garden display.

Zinnia Flower Development

Acquiring continuous flowering can be a challenge for many gardeners and growers. The major reason is that once the first bloom is harvested, it will take some time before branches form and reproduce new flowers. Throughout this period, expect no harvest. So what you could do is to plant them at intervals, especially if you want consistent production of flowers to sell. Research in Kansas has shown that in order to achieve continuous harvest, 7 to 8 plantings are recommended.

  • Medium-height: Plant these varieties in two seedings at 2 to 3 weeks interval period, depending on soil temperatures at sowing time. Varieties include Ruffles, Pumila and Cut-N-Come Again.
  • Large-height: Plant these varieties several times in succession. The second planting must be made two weeks after the first planting then the succeeding plantings must follow a one week interval. Flower varieties include State Fair, Orange King California Giant, and Benary’s Giant Series.

Watering Your Zinnia Flowers

It is imperative to obtain supplemental irrigation, particularly if you are situated in hot and dry location and producing specialty cut flowers like Zinnias. It is best to water the plants early morning to allow flowers and foliage to dry before night fall. Also, excessive water is dangerous to Zinnias.

Overhead watering must be avoided as it can damage the flower such as spottings on the petals, mildew and other plant diseases. Instead of spraying the leaves, sprinkle water directly into the soil using a soaker hose. This will keep the petals and leaves dry while giving sufficient water supply. Better yet, construct a drip irrigation to directly apply water on the ground, not on the leaves and flowers.

The weather and growth of your plants will determine how much and how frequent you must water them. The soil moisture status in the root zone will help you schedule the irrigation. Keep in mind that inadequate watering will decrease quality and production, where as waterlogged soils may cause root rot and hamper growth of the plants.

Zinnia Care

Do regular deadheading to prevent reduction of blooms and short lifespan of your Zinnias. Additionally, once you notice a sickly little plant amongst your Zinnias, pull it. The best thing to do here is to keep a flat of seedlings standing by and start new plants every few weeks throughout the growing season.

Zinnia Pests and Plant Diseases

Prevention is better than cure. Growing healthy Zinnia plants and keeping the planting area as weed-free as possible make it a lot easier to control pests and avoid plant diseases. Make sure to monitor your Zinias closely for any signs of insect attack or plant disease. Once you detect an insect attack, control it immediately before infestation occurs. The most common insects that attack Zinnias include caterpillars, stem miners, thrips, aphids, and leafhoppers. The last three insects mentioned may also transmit viruses.

Muddy or wet soil causes Zinnias to wilt. Fungal and bacterial growths also thrive in wet soil. Aster yellows, Alternaria leaf blight, and powdery mildew are some of the major plant diseases that affect Zinnia plants. Periodic application of fungicide might be needed to control powdery mildew. Just make sure to identify the correct disease first, and follow directions on the fungicide label. You may also interchange planting beds every year to prevent build up of soil borne nematodes and fungal pathogens.