Tips for fast finishing

"Time is money! Money is time!” I am not sure to whom to attribute this quote, but it is certainly apropos in the greenhouse world — especially in spring!

The spring bedding plant season is the most valuable time in the greenhouse, as it represents the majority of greenhouse crop sales. One of the characteristics of spring that makes it so challenging is how quickly the season goes. Given this crazy production schedule, are there places we can find to shave off a little time?

The cumulative gains from small tweaks may allow you to finish crops more efficiently. You can start production a bit later, saving on labor and energy, or perhaps you’ll take the open bench space to finish another crop. Either way, let’s look at some time-saving strategies.

Start out with a solid crop schedule. Putting together a plan will help you minimize any excessive bench time the crop may have. Without a schedule, I think we tend to lean on having things ready early “just in case.”

But being put in the place of having to hold crops results in unnecessary and unwanted extra plant growth to manage, as well as more labor and resources to do it. Use the technical sheets the genetics companies provide, books with crop production information and — most importantly of all — your own notes from previous years to put together a solid schedule. Then, stick to it!

Another way to manage your crop time is by modifying the size of the starting material. All other things equal, a larger seedling plug or rooted cutting liner will finish faster than a smaller plug or liner. This is simply due to the maturity of a larger plug — more leaves have unfolded, more axillary buds are turning to branches, etc.

As a result, the time from transplanting to flowering (or finishing) for larger young plants is less than smaller ones. But keep in mind the savings in bench time with larger starting material — it may well work out in your favor.

Another opportunity is to increase the number of plugs or liners to reduce finishing time — for instance, starting a 1-gallon perennial with two young plants instead of one, or a hanging basket planted with seven plugs instead of five. While it will increase costs, the reduction in time to fill in and finish containers may pay for it, plus some.

While everybody is looking for ways to save on energy costs, reevaluate the strategy of growing cool. While heating a cool greenhouse costs less than heating a warm one on a day-by-day basis, growing too cool can actually end up wasting more energy, as well as time.

As air temperatures decrease, the rate of crop development (i.e. leaf unfolding and expansion rates, flower bud elongation rate, etc.) slows down, which in turn increases the total time required to finish the crop. While some species (i.e. petunia, pansy, snapdragon) are tolerant of cold temperatures, many favorite spring crops are less so. Rethink decreasing the air temperature too much for cold-temperate (i.e. dahlia, lobelia, verbena) and cold-sensitive crops (i.e. angelonia, New Guinea impatiens, pentas) and provide them with sufficient heat to finish in a timely manner.

While we commonly think of flowering control for flowering potted plants like poinsettias, chrysanthemums and kalanchoe, many spring annuals have similar mechanisms of flower induction. The daylength or photoperiod is a common mechanism for flowering control for many spring annuals.

While there are certainly day-neutral annuals that flower regardless of daylength (bedding and New Guinea impatiens, geraniums), many bedding plants flower in response to long days (petunia, pansy, dahlia).

For these long-day plants, simple night-interruption lighting is sufficient, where a minimum of 2 µmol·m-2·s-1 (or 10 f.c.) from 10 p.m. to 2 a.m. is sufficient to promote flowering. For some crops, especially those in smaller containers, consider inducing young plants to flower prior to transplanting. Not only will it help reduce production times for small containers, but it is also an energy-efficient approach to light plants when they are on closer spacings at higher densities.

Finally, pinching is a common approach to enhance branching for many spring crops. However, it is a labor-intensive approach, even when time-saving strategies such as automated shearing or shearing liner trays prior to transplanting are used.

Two plant growth regulators (PGRs) on the market for enhancing branching are cytokinin benzyladenine (BA; Configure) and the ethylene-generating compound ethephon (Collate, Florel). Since ethephon products can also delay flowering, these are not as useful for short term (i.e. finishing time of five weeks or less) production schedules. Applying BA as a foliar spray to containers after transplanting can enhance branching for many species, as cytokinins counteract apical dominance and let axillary branches develop.

Hopefully, these tips provide you with some opportunities to shave a little time off your production schedules. None will be a silver bullet, but their additive effects may have a larger impact on your production times than you may think.