September into October is my favorite flower time. The bustle of summer has slowed down, and the flowers are consistent week after week (with the added benefit of hardy annuals reblooming to add interest). Dahlias and zinnia steal the show. When done right, the supply of blooms is seamless and it certainly looks easy from the road.

The reality is that there is an art and a science to extending our season to fall frost. As I’m planning for next year, I’m grateful for what works well season after season. Succession planting is our friend as commercial growers. What works for gardeners does not always make sense in the field. Labor is one of my highest inputs so reducing fussing in the field by turning over beds helps me produce more flowers in a smaller area. I can cut my zinnia back for another flush, but those plants will only produce one useable stem each time I do this, as opposed to the three blooms that come immediately on a pinched fresh plant. Cut-and-come-again plants do get tired and although they keep producing, they’re not as proficient as fresh plants.

Simply put, succession planting is planning crops so that they bloom at multiple harvest times. There are two ways to accomplish this. The first is to plant the same variety several weeks in a row. The other is to select varieties with different days to harvest and plant at the same time. I use a combination of both.

The obvious advantage is a consistent harvest over a longer season, but this technique also avoids pest issues such as Japanese beetles or thrips and offers replacements for plants taken out by diseases such powdery mildew. To beat both of these challenges, I wait to start seedlings of valuable zinnia then transplant out the first batch. They mature after the worst of the damage has passed and are more apt to produce double blooms.

Photo by Betsy Busche

Seasonality is another reason to keep planting. I need different colors at times that may not naturally produce. Rudbeckia reads autumn but blooms in July. Ageratum is a workhorse late season but the blue is hard to incorporate in autumn bouquets without it screaming spring. I grow autumn sunflowers so that every bouquet gets one to temper the brightness of zinnia and other tender annuals. I have also found that sunflowers bunches sell better in fall to supplement mums and pumpkins.

There are flowers and vegetables we do this with every season. Corn and sunflower growers use staggered plantings to create a steady supply from summer until frost. As I talked about last month, these are single stem plants that produce and then die off. The flowers are valuable enough that the plants can usually be spaced at six inches to make this worthwhile.

To have a continuous supply, we need to understand two factors directly related to blooming triggers. “Days to Harvest” is the approximate amount of time required for the plant to mature and bloom. Weather and other factors impact this, but we use an average span to plan. Many professional catalogs provide this number, but sometimes it’s calculated from germination and other times from transplant date. I create a cascade of varieties that bloom a week apart.

Gladiola is a great example of a single stem flower with varieties with many dates to choose. It’s easiest to see in mixes, as yellow is always first (for tulips too!), followed by other colors. The range is 65 – 90 days. My main use of glads is as a spike in bouquets. To have more control over style, height and color inherent in each variety, I pick five that stagger over four weeks, then plant the sets three times a week apart. I pick brighter colors for summer and more moody colors into fall to help zinnias appear more autumnal. I’ve learned thrips do a lot more damage with later plantings, but certain varieties hold up better against them. All of these characteristics fit like pieces in a puzzle that help me grow the best plants consistently.

The other concept is daylength (the number of hours of darkness required for a plant to bloom). Daylength-sensitive crops include cosmos, goldenrod, rudbeckia, Shasta daisies and many of the perennials. The famous daylength-sensitive plant that defies succession planting is godetia. This poppy-like bloom is direct-seeded as soon as the soil can be worked. I tried adding two successions and they all bloomed at once, but the later ones were on shorter stems.

The last weeks of the season I depend on cosmos as a filler. I transplant a single variety every two weeks that I pinch at about a foot tall. This is a short day plant that thrives in autumn. I need the leaves to be healthy and the blooms to be consistent, as I bunch four to five stems in the center of every bouquet. I harvest just as the first bud opens so the rest will follow. The plant is branching and when cut deep it will produce more stems. I count these as helpful bonuses, but not something that I can count on week after week. I also use tall branching gomphrena the same way and need the foliage to be pristine.

Each year I push the last date to transplant in August to see what I can get away with. This year I had basil as filler in late September. These were the prettiest and healthiest plants of the season. It’s really exhausting to be still starting seedlings in midsummer when there is so much to do, but the rewards in autumn are worth it. I often assign a dollar amount to these crops for motivation, hoping for that elusive extra thousand dollars every fall.