How (and Why) We Succession Plant
Sowing seeds for our summer tender annuals in stages to ensure a continuous harvest of fresh flowers
Each spring and early summer, we make a series of plantings of some of our favorite tender flowers and foliages - including zinnias, cosmos, love-in-a-puff, dahlias, and Persian cress. This process, referred to as “succession planting” allows for a longer harvest window of these popular, well-loved flowers, and is integral to our custom-growing schedule.
Why We Succession Plant
Many tender annual cut flowers, if started from seed in the spring (often in March indoors or May outdoors here in Greater Philadelphia, Zone 7a) will begin blooming in June or July. These annuals, which complete their entire lifecycle in one growing season, prefer warm weather and will die during the first frost, which most commonly occurs in late October. Some varieties provide a relatively steady harvest of flowers from June or July until this first October frost, but many of the plants get “tired”, struggle with disease, or the flowers simply become less usable or fresh-looking after a month or two of blooming. Zinnia seeds started indoors in March are not likely to still be producing beautiful flowers in September or October, for example; most will have succumbed to powdery mildew (a frustratingly common fungal disease) following the hot, humid summer.
As a result, in order to ensure a continuous harvest of fresh, beautiful flowers, we start them in stages. It’s especially integral as part of our custom-grow process, as we will start many of the tender annual seeds for our September and October weddings as late as June or even July to ensure they are in optimal condition for our fall brides and grooms.
How to Succession Plant
In order to harvest backyard bouquets from summer through fall, it’s best to plant them in intervals. As a general rule of thumb, I’d recommend starting most fast-growing tender annual seeds about 3-4 weeks apart from spring through mid-summer. If you have a packet of 100 zinnia seeds, for example, I’d start about 25 in late-March indoors, another 25 in early May outdoors after the last spring frost, 25 more in June, and the final 25 in July. By the time the first succession is slowing down in production, the next succession or two will be hitting their stride.
Some “single bloom” or “one and done” varieties can be started in even shorter successions. Most sunflowers, for example, yield just one flower per plant. To ensure sunflowers blooming all summer long, most flower farmers recommend sowing seeds about 10-14 days apart.
Succession planting also gives growers the ability to maximize their garden space during each floral microseason. Once the cool-weather flowers have wrapped up, we plant the second or third succession of many varieties in their place. For example, when the sweet peas along a vertical trellis begin to peter out in late June or early July, we replace them with Love-in-a-Puff seedlings, that will climb the same trellis. Similarly, the area where we grow larkspur in late spring is flipped in early July to accommodate our final succession planting of zinnias.
What Seeds to Succession Plant
I highly recommend succession planting for any gardeners growing zinnias, cosmos, sunflowers, and two of our favorite foliages - Persian cress and love-in-a-puff. We also tend to plant our dahlia tubers in stages, depending on when we would like each variety to be at their peak blooming window. This year, for example, we planted about half of our dahlia tubers in late April for our weddings from mid-August through September. The dahlia tubers intended primarily for our October weddings didn’t get planted until early June. Because dahlias are particularly susceptible to disease, and tend to slow in productivity after a month or two of blooming, this gives them the best chance for stunning flowers in early fall - the time of year that they naturally want to produce the most (they’re a “short-day” plant!).
