Best practices for preparing plants for shipping

How can we best prepare our annual and perennial bedding plants for shipping and retailing? By producing a plant that is toned and resistant to diseases.

Many of the recommendations provided below are to help produce harder growth, while maintaining healthy and marketable appearances, and they should be used together for the best possible results.

While some growers will acclimate tropical plants for the lower light intensities plants will experience in interior environments, no such acclimation needs to take place with annual and perennial bedding plants for shipping in trucks. The opposite strategy is taken, exposing plants to high light to tone their growth and enhance photosynthesis. In order to grow good, quality annual and perennial bedding plants, achieving a photosynthetic daily light integral (DLI) of 10 to 12 mol·m^–2·d^–1 is the goal.

Higher light intensities are great for toning plants and preparing them for shipping. With higher light, plant growth will be the harder growth we want, avoiding soft growth that may be damaged in shipping. In addition to plant growth, the enhanced photosynthesis from higher light is sure to increase carbohydrate reserves in plants, which will be useful for maintaining quality during shipping and retailing.

Reducing air temperatures is a great strategy for hardening plants off and preparing bedding plants for shipping and marketing. Like higher light intensities, cooler temperatures promote harder growth and thicker leaf cuticles, allowing plants to better withstand mechanical damage in transit and at the hands of consumers. Keep in mind the tolerance of plants to cooler or colder air temperatures is related to their base temperature, which varies among species. Don’t let temperatures drop to the point of causing chilling injury to cold-sensitive plants while trying to harden cold-tolerant plants when they are grown in the same environment.

Leading up to shipping, fertilizer should be provided to maintain healthy looking foliage and flowers while minimizing excessive stretch and soft growth. Restricting nitrogen and phosphorous concentrations at the end of production will help moderate leaf expansion and stem elongation. Be mindful to treat symptoms of nutrient deficiencies if they appear. Key symptoms to look out for include yellowing (nitrogen deficiency) or purpling (phosphorous deficiency) of lower leaves, as this could reduce marketability. Maintaining sufficient magnesium and micronutrient concentrations in fertilizers at the end of production will help maintain green foliage without promoting additional growth.

While plants are being toned to prepare for shipping, growing crops on the drier side can help prepare them for shipping and retail. Much like higher light and cooler air temperatures, growing crops on the dry side can help promote harder growth, which suppresses excessive leaf expansion and stem extension. It also promotes more cuticle development on leaves. Although growing plants dry leading up to shipping is a good practice, plants should not enter the shipping and marketing chain with dry growing substrate.

Plants should be well-watered prior to shipping to ensure they have available water in the substrate. However, while it is important plants are well-watered before shipping, care should also be taken to make sure foliage is not wet when plants are placed in boxes or on racks rolled into trucks. Free moisture on leaves and flowers can result in diseases developing, therefore reducing quality and marketability.

Sometimes applying plant growth retardants (PGRs) at the end of the production cycle for bedding plants can improve their performance during shipping. (Editor’s note: For more on plant growth retardants, read “Getting started with plant growth retardants” at https://bit.ly/PGR-101) However, consideration needs to be given to how any PGR application at the end of production will affect the plant performance for consumers. For those annuals grown in flats or smaller containers — container sizes which are bound for transplanting into garden beds or large containers — the residual activity of any PGR application should be minimal.

This would mean using active ingredients with a short residual activity such as daminozide (Dazide, B-Nine), using lower concentrations of active ingredients, and/or using foliar sprays (and avoiding drenches or sprenches). For larger containers, like hanging baskets and patio pots, stronger PGR applications using active ingredients with longer residual activity, higher concentrations, and sprenches and drenches can be used to hold crops at the end of production, since these items are purchased to enjoy “as-is.”

One of the last things to be done to prepare plants for shipping and marketing is to improve their resilience to pests and diseases. To avoid root rots and botrytis while plants are being shipped, fungicide applications are very useful. However, the same care must be taken with fungicide applications that are used when irrigating crops — foliage should be dry as plants are going into boxes or trucks. Apply fungicides a few days prior to shipping to avoid wet leaves. If a last-minute application is made and plants are shipped wet, it can actually enhance the development of diseases like botrytis and make it worse.

Take the time to correctly prepare your plants for shipping and sales. From propagation through production, efforts are taken to grow a great plant. Maximize the results of these efforts by sending off the best plants possible. Hopefully the tips outlined in this article will help you do just that.