For the person hoping to add easy to care for greenery to their home, succulents seem to be the way to go. Once seen as trendy, it now appears the popularity of these plants are here to stay. Growers looking to add succulent production to their operations need not fear.
W. Garrett Owen, Ph.D., of Ohio State, and Roberto G. Lopez, Ph.D., of Michigan State, presented “Succulent Production: Managing pH, Fertility, Temperature, Light and PGRs” – essentially a how-to guide – at the most recent Great Lakes Expo.
Lopez noted that from 1997 to 2019, the sale of succulents increased 218% (from $22 million to $70 million). “But ‘succulent’ is more of a marketing tool than a classification,” he added. The only thing linking most of them is that they belong Crassulaceae (stonecrop or orpine) family.
The problem with getting started in succulent production is they are slow growing, often taking four to eight months to reach marketable size. Many also require unique growing conditions and they can be difficult to propagate and produce in temperate and northern climates.
Lopez said limited research has been conducted to determine if environmental parameters such as light and temperature can be utilized to hasten production, as well as plant growth regulators (PGRs) to improve consumer success.
He looked first at temperature and the daily light integral (DLI). “The perception is they need higher temperatures and light amounts,” Lopez said. “Experiments have shown that that’s not true across the board.”
Their experiments looked at a variety of plants at different temperature ranges (61º – 72º F, 66º – 77º, 72º – 82º, 77º – 88º and 82º – 93º; a second experiment started lower, at 55º – 67º). All plants received 12 hours of daylight and 12 hours of night.
Lopez reported that some plants saw better growth in that 60º – 70º window, including Aeonium nigrum, on which temperature had a greater impact than DLI. With Senecio ficoides and A. haworthii ‘Kiwi,’ leaf color changed depending on temperature, with more color appearing when they were cooler. S. ficoides did better with less DLI. Other cool temp lovers included A. arboretum and S. fulgens.
Doing well at 65º – 75º were Cotyledon orbiculata ‘Silver Peak,’ Echeveria ‘Pollux’ and ‘Purpureum’ and Pachyveria ‘Corvus’ and ‘Opalina’ (which liked more light). Also enjoying this cooler window were Kalanchoe tomentosa and ‘Villiosa.’
From these experiments, Lopez’s team concluded that temperatures higher than 77º resulted in decreased growth and development for some genera and species and increased growth for others. DLI, however, had little impact on plant growth and development.
The next issue Lopez tackled was the fact that succulents tend to grow great in the greenhouse but can grow too big when the consumer brings them home. This could be due to low light during shipping, unrealistic marketing and indoor quality that can lead to stem elongation.
They looked at PGRs paclobutrazol and uniconazole and wondered if a single drench would work for growth control. When plants in this experiement were of marketable size, they were given a drench of either 0 – 8 ppm of paclobutrazol or 0 – 4 ppm of uniconazole and then moved to a “windowsill” environment. They found the paclobutrazol drenches were very effective with Cotyledon, Echeveria, Graptopetulum ‘Debbie’; uniconazole worked well for Pachyveria.
“A single drench is quite effective in maintaining quality for consumers,” Lopez said.
Owen took over to discuss pH issues. “We do not know the optimal substrate for pH for succulents,” he admitted. His team looked at 15 different species and found no symptoms of iron or manganese toxicity with a low pH, and a high pH did not affect plant growth as much as ornamental value.
As for the fertility needs of succulents, Owen said if they’re insufficient, growers will see lower leaf or whole plant chlorosis, reduced branching, delayed or total lack of flowering, stunted plants and low quality plants. If there’s excessive fertility added, though, growers could see other problems, including marginal leaf necrosis, root-tip necrosis, vigorous or stunted plants and low quality plants.
In the results of his experiments, Owen’s team found that for all 21 species examined, the height, diameter, growth index and plant dry mass increased as their nitrogen concentration increased, although to different magnitudes. In general, growth plateaued at 125 – 200 ppm nitrogen. At anything lower than 75 ppm, plants exhibited lower leaf reddening.
“Overall, the research demonstrates genera-specific fertility requirements to optimize growth, as well as establishing more precise nitrogen concentrations,” Owen said. “Growers should strive to provide 125 – 200 ppm nitrogen during succulent production.”
by Courtney Llewellyn