Most of us remember the tall annual zinnias our grandparents grew along the picket fence in the backyard and the knee-high version that grew along the foundation of the house. Most of the flowers were large and had lots of petals. Their colors were almost always bold and bright. While these beautiful types of zinnias are still popular annuals, they are no longer your only choice. Plant breeders took an interesting species,
Z. angustifolia and improved it, resulting in compact, spreading plants with small, narrow leaves. They are disease resistant and can literally cover themselves with small single flowers. In 1997, the variety 'Crystal White' was an All America Selection and the Star series ('Starbright', 'Star Gold', etc.) offered some great color choices. One of the most exciting recent developments in the world of zinnias has been the new ‘Profusion’ zinnias. They are compact plants growing just 12-16 inches with dozens of 2- to 3-inch single flowers in orange or cherry red. Other colors are being added each year. Unlike so many older types of zinnias, Profusion zinnias rarely have disease problems and need less deadheading than traditional varieties.
In the world of zinnias, there are several different flower forms. Zinnias can be either single (with just one row of petals around a center), semi-double (with 2 or 3 rows of petals) or fully double (with several rows of petals often hiding the center). The flowers on doubles can look like buttons, cactus flowers or dahlias. Zinnias are available in almost every color except blue. There are even bi-colors and one variety that is chartreuse.
Zinnias work well in the garden or in containers and make great cut flowers. Planted in a large mass, they make a bold statement. The older varieties are more upright and work well toward the back of borders. The newer varieties are more compact and tend to grow almost as wide as tall. They can be used in containers and in the front of borders.
Zinnias are sensitive to frost and shouldn't be planted out in our area until mid- to late-May when the air and soil temperatures are warm. They are sun-loving plants and ideally should be planted where they will receive direct sun at least six hours a day. They will also survive if they just get afternoon sun or in a very high light situation, but they may not bloom as well and may be more susceptible to disease problems. Zinnias are native to Mexico and once they are established, they are drought tolerant plants. Keep them evenly moist while they are growing rapidly early in the season so they develop an extensive root system. As summer progresses, they become more and more drought-tolerant.
Zinnias grow in almost any soil as long as it is well drained. Their drought tolerance makes them a good choice for sandy soils. Zinnias aren't heavy feeders. Try mixing a slow-release fertilizer such as Osmocoteä or an organic such as Sustane into the soil when they are planted and then fertilize them monthly with a water-soluble product such as Bachman's Mighty Bloom™.
All older zinnias are suitable for cutting. In fact, one variety is called 'Cut and Come Again'. The old standard for a large flower with a long stem is called 'State Fair' and there are lots of newer improved varieties. Check the package or the tag for plant height. If it's more than 18 inches, it will make a good cut flower. Ideally the flowers should be cut just as they begin to open and the stems should be immersed immediately in lukewarm water. Flowers that are cut in early morning tend to have more moisture in them and they keep longer. Handled properly, cut zinnias look good for at least a week. Zinnias can also be dried using silica gel for a lasting bouquet.
When you choose the right variety, zinnias are great in containers. 'Crystal White' and the Star series grow 10-14 inches tall and wide, making them good candidates for large containers. Containers dry out more quickly than the ground, so be sure to keep them moist. Occasionally you will find the large varieties in plants, but most often they have to be bought as seed. The more compact varieties such as 'Profusion', 'Peter Pan', 'Dreamland' and 'Pincushion' are commonly sold as plants. Over the past few years, more and more garden centers are also offering Star series and 'Crystal White' zinnias as plants.
Start seeds directly in the garden when the soil is warm, they germinate in just 5 to 7 days and, once germinated, they grow quickly. If you are going to start the seeds indoors, don't begin before early April or they will be too big to manage before it is warm enough to move them outdoors. If you plan to sow the seeds directly in the garden, wait until late May when the soil has warmed above 60º. It is important not to crowd the seedlings to keep good air circulation and avoid problems with damping off (a condition where seedlings suddenly fall over). When starting any of the larger types of zinnias, it is easiest to plant them directly into individual containers. They grow quickly and need lots of space.
All varieties of Zinnias are capable of blooming from early summer until they are frosted in fall. However, the older varieties will need to be deadheaded on a regular basis or the plants will switch their energies to setting seed instead of developing new flowers. The newer Profusion zinnias and
Z. angustifolia varieties don't have to be deadheaded to keep blooming, but you may want to snip off some old blooms occasionally just to make the plants look better.
Some varieties of Zinnia have a problem with powdery mildew. There are several steps you can take to avoid powdery mildew. First, select a resistant variety such as 'Profusion' or any of the
Z. angustifolia varieties. Another key is to plant them where they get lots of sun and good air circulation. Space them out and be sure they aren't crowded by surrounding plants. Whenever possible, water zinnias from below so the foliage stays dry. If you are growing a susceptible variety or if the zinnias are growing under less than ideal circumstances, they can be sprayed routinely with a fungicide to protect them from powdery mildew. Occasionally zinnias develop some spots on the leaves and the flowers. This is caused by fungal diseases that need humid conditions to thrive. Fortunately, we don't often see this type of disease on zinnias in our climate.
Zinnias seldom have problems with insects. If you do have an occasional problem with aphids, try to wash them off with water or use a mild pesticide such as insecticidal soap or pyrethrin.
Additional Bachman's Information
Fertilizing Annuals and Perennials
All About Watering
Starting Seeds Indoors
Recommended Products
Zinnia Plants
Seeds and Seed Starting Supplies
Bachman's Mighty Bloom™
