As August fades, the garden gives us one last big push of flowers. The late summer annuals tend to have lots of great color, fabulous texture, and are generally easy to grow and pest resilient. It's a nice time to be a gardener...and a florist.
The quintessential summer flower must be the zinnia. A cutting garden workhorse, it is easy easy easy from seed, and pumps out tons of blooms for weeks on end. More recent zinnia breeders have given us some beautiful new forms and colors, and of course I gravitate toward the unusual.
My favorite in the zinnia group must be the Zinderellas. In both lilac and peach (and I've seen more colors being added to this series), they combine with most any bridal palette.
And I don't even care that 90% of the blooms are singles. I still think they are most charming. And the florists still buy the singles. And the brides still love them.
Because we have very limited garden space, I have had to pair down my zinnia varieties significantly, but still grow Oklahoma Salmon, Oklahoma White, Queen Red Lime, Benary's Giant Salmon Rose, the Zinderella series, and Jazzy mix in large amounts.
Zinnias aren't long lasting cut flowers. They'll happily give you about four to five days in the vase with frequent water changes. We harvest the flowers early in the day, give them a dunk in the quick dip, and keep them in our warmer cooler (44 degrees) to condition before using in design work. Zinnias kept in a cold cooler quickly lose their luster, getting dry around the petal edges and their brilliant colors fade a bit. If in doubt, keep them in an air conditioned space instead.
Timing the harvest is essential. To determine if the flower is ripe for cutting, place the stem between two fingers and wiggle it side-to-side. If the flower flops around like the neck of a newborn baby, it's not ready. Wait until they shake stiffly, like a weeble. Cut somewhat deeply to give you ample stem to design, but make sure to place your cut just above a node (a pair of leaves), and preferably a node with a side shoot just waiting for it's moment.
Members of the aster family (Asteraceae) and native to North American desert regions, Zinnias can tolerate (and thrive in) hot heat and low water conditions. They practically train new gardeners with their ease of care. Transplants are ready in about three weeks, and wait too long and plants will become unhappy in their plug trays. In our zone 5b climate, I don't start zinnia seeds until mid-May.
We have been able to circumvent common pest issues in the zinnia patch by carefully choosing planting times and location. Come late June, the Japanese beetles are in full-force, checkered napkin in their collar and knife and fork in hand to begin their week's long feast and devastation of many cut flower and food crops. As they are non-native pests, they lack natural predators in the US and are allowed to take over for their short lifespan as adults. Pheromone traps don't work, other controls are expensive (and also probably don't work), so you can fervently hand-pick and drown the insects, or wait out the infestation, as the beetles only live for about a month or so.
We don't attempt an early crop of zinnias. They much prefer a warm soil, and the plants will get beaten up by the pests in late June. In fact, I have planted out a crop of Zinnias in both early and late May, and got flowers from both crops at the exact same time. The only difference is that we spent more time (and money) weeding the early crop. Timing your zinnias so that plants are established and healthy, but not yet blooming come late June is our key to success through the infestation.
Zinnias are also often plagued by powdery mildew here in the hot and dry Midwest summers. This disease is caused by several species of fungi, and spreads rapidly in times of year where days are dry but humid, breezy with cooler nights. The leaves turn a less-than-lovely powdery color, and growth is affected. I've found keeping my Zinnias sheltered from the breeze tends to help, as well as hoping for consistent rains and favorable weather conditions to keep the disease at bay. So far, this has been the least damaging year for our zinnias.
For cut flower farmers in zones 5 and warmer, it is most prudent to plant two rounds of this cut-and-come-again crop. By the time the first crop loses it's energy and succumbs to mildew around mid-August, your second round will be just coming into bloom, giving you many more stems until frost. I plant my more summery colored zinnias in the first round, and save the moodier ones for the second.
Zinnias can be lovely, even elegant, in design work. I enjoy them combined with pedigreed flowers like garden roses and foxglove. A cheerful accent.