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To top off this impressive resilience , no fertilizer was added to the reservoir for more than eight months and the plants survived , thrived even .”
Usually , students are responsible for everything to do with the horticulture program at the school which consists of three garden towers and a lab where seedlings and cuttings are propagated and studied . The lab technicians are trained to start plants in stonewool , load the net baskets with plants , mix nutrient solutions , monitor and adjust the reservoir level , pH , and electrical conductivity , and to perform basic repair and maintenance that has kept the towers running for the past seven years . The only problems we have had with the units are occasional kinked hoses and failed pumps which we replaced with upgraded ones . Students don ’ t generally do the thorough cleaning required between runs . Guess who gets to do that ? I say usually the students are responsible for everything , but the 2020-21 school year was anything but usual . Due to the pandemic and precautions taken , only one tower was operational this year and it ran unattended for extended periods . The reservoir ran dry on at least one occasion , but the upgraded pump survived no problem . Other times the plants were reported to be severely wilted , though the addition of water brought them right back . To top off this impressive resilience , no fertilizer was added to the reservoir for more than eight months and the plants survived , thrived even , on just water and whatever nutrients were introduced by decay of roots and microbial action . In an example of how we use spider plants in STEM ( science , technology , engineering , and mathematics ) education , a couple of students performed a series of experiments testing how the number of root initials on a spider plant cutting affected the later successful growth and development of the plant ( Fig . 2 ) shows a graph of one result of this work . It shows that , on average , you can expect about one more root to develop than is visible as a primordia on a cutting . Note that the most primordia typically visible on a plantlet ( also known as a spiderling ) was nine because we collected plantlets as often as we could from about 20 stock plants in hanging baskets . However , after the recent extended growth period without harvesting , many of the tower-grown plantlets had more than 20 well-developed root initials ( Fig . 3 ). Other experiments have shown that the more root initials there are on a cutting , the better the chance of survival after transplant . Each net basket started out with one plantlet rooted in stonewool , but now the baskets have three or four plants producing many plantlets each . When the tower was recently brought home for the summer , 241 plantlets with welldeveloped arial root initials were harvested and transplanted into soil ( Fig . 4 and 5 ). We hope to sell them at a fundraiser next school year to support more hydroponics research .
Fig . 2 . Number of primary roots vs . number of primordia of C . comosum after 20 days in a growth chamber ( mean ± SEM ). Number below each point is the number of samples for that number of primordia . The equation for the line of best fit is y = 1.05x = 1.77 , R2 = 0.92 .
Fig . 3 . Spiderling with many well developed root initials .
Fig . 4 . 241 spider plant cuttings ready for transplant .
There is much to recommend the spider plant as a candidate for hydroponic / aeroponic propagation : they handle neglect well , reproduce quickly , really fill out a tower , and people like them . One disadvantage is the mother plants are so tightly jammed into the tower openings that they are impossible to remove without disassembling the tower one level at a time . Oh well , I guess we ’ ll have to leave them there and let them make more spiderlings .
Philip McIntosh is a science and technology writer with a bachelor ’ s degree in botany and chemistry and a master ’ s degree in biological science . During his graduate research , he used hydroponic techniques to grow axenic plants . He lives in Colorado Springs , Colorado , where he teaches mathematics .
Fig . 5 . Transplanted spider plant cuttings .
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