Propagating Chili Peppers on the ISS

Updated: Jun 21

With an innovative blending of controlled-release fertilizers



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Astronaut Posing For the Camera and Growing Vegetables in Space

Written by

Ed Rosenthal, STHOF Collaborator, Space Plant Biology VEG-04/05 KSC, Certified Space Foundation Technology Educator, USA and James Cawley, News Editor, NASA.gov, USA


Article Reprinted from the November-December 2021 of Fertilizer Focus


The Innovative blending of controlled-release fertilizer types by the NASA Space Plant Biology Team at Kennedy Space Center has resulted in a profuse flowering of chili pepper plants on the International Space Station. chili peppers were recently propagated by NASA on the ISS, and are being grown for the first time in space in the Advanced Plant Habitat-04 (PH-04) experiment.


The chili peppers being grown in the APH, is in addition to NASA space food production research which are grown in the Vegetable Production System or “Veggie”.


In the APH, NASA has successfully used Nutricote® 18-6-8 T 180 day from Florikan®, to previously grow wheat and the model plant Arabidopsis thaliana in the APH large plant chamber on the ISS.


NASA space crop production group planted seeds of the Española Improved NuMex chili plants in the APH, using a blend of Nutricote 14-4-14 T 180 day and Nutricote


14-4-14 T 100 day CRF, blended with Gal-XeONE® CRF 0-0-19 + 9% Mg T 70 day into a high CEC soilless media called Arcillite®.


Scientists working in the lab with vegetables and controlled release fertilizer

Dr. Gioia Massa, NASA payload scientist for Veggie, left, Betty and Ed Rosenthal, founders of Florikan observe ground control experiments in the Veggie Lab at NASA’s Kennedy Space Center.

Photo credits: NASA


One of the keys to the profuse flowering of the chili peppers is the reduced nitrogen (N) blend with a higher potassium (K) content in a controlled release fertilizer matrix, which is

programmed to release at the high K to N ratio over two to six months.


Being able to precisely control the release rate of nitrogen in ratio to a higher release ratio of potassium is critical in achieving the compact morphology required to grow chili pepper plants in APH. The success of the flowering is attributed to a blend containing a controlled release of K with the K ratio.



Pepper plants growing onboard the international space station (ISS)

Four pepper plants growing aboard the International Space

Station; Photo credits: NASA



increasing to release continuously at higher levels than the N. At an approximate 2K:1N ratio the chili peppers flowered extremely well. “The goal was to limit early N availability to

prevent the plants from getting too big early on,” said Matt Romeyn, principal investigator for PH-04.


Multigenerational studies

According to a NASA news release, the four chili pepper plants growing aboard the International Space Station in the Advanced Plant Habitat (APH) bore fruit – several peppers. Peppers are self-pollinating, and once pollination occurred, peppers started forming 24 to 48 hours later. However, not all pollinated flowers developed into peppers.


Dr. Gioia Massa also has had positive results with tomatoes in Veggie hardware with the fertilizer blend of 14-4-14 CRF blended with CRF 0-0-19 + 9% Mg T 70 day. Dr Massa comments; “What we have learned with peppers is also a great foundation for our work with tomatoes. We are currently growing tomatoes on the ground in preparation for ISS testing within the Veggie hardware, and we are testing similar formulations to the peppers and getting good results so far!”


NASA explains the APH is a fully automated facility, that is being used to conduct plant bioscience research on the space station. The hardware is a large growth volume plant habitat, capable of hosting multigenerational studies, in which environmental variables (e.g. temperature, relative humidity, carbon dioxide level, light intensity and spectral quality) can be tracked and controlled in support of whole plant physiological testing and bio-regenerative life support system investigations.


In a written statement, NASA explained, that a unique feature of the APH is that it can be controlled remotely. To pollinate the flowers in orbit, the team at NASA’s Kennedy Space Center instructed APH to run its fans at variable rates to create a gentle breeze in microgravity to

agitate the flowers and encourage the transfer of pollen. The space station crew also provided assistance by hand pollinating some of the flowers. The controlled release fertilizers did a great job fertilizing the peppers by encouraging flower set and keeping the nitrogen low which reduced stretching.


Pepper plants beginning to Flower on the international space station (ISS)

Chile pepper plants growing in the Advanced Plant Habitat (APH) aboard the International Space

Station recently bore fruit. Photo credit: NASA/Megan McArthur



Plant experiments

Why Peppers? NASA explains that peppers contain several key nutrients and are an excellent source of Vitamin C. The plants are easy to handle in microgravity and are a pick-and-eat crop that does not require cooking or complex processing. The peppers also have low microbial levels, so they are safe for astronauts to consume.


Four pepper plants growing in the Advanced Plant Habitat (APH) aboard the International Space Station have sprouted several flowers recently and NASA astronaut Megan MacArthur shared photos of some of the first flowers blooming. These flowers are developing into edible chillis that astronauts will sample later this year.


A team of plant researchers at NASA’s Kennedy Space Center has closely monitored the peppers as they flowered and run the APH’s internal fans at variable speeds to create a gentle breeze inside the growth chamber to assist in pollinating the peppers.


The Plant Habitat-04 experiment is one of the most challenging plant experiments to date, in part because of the long germination and growing

times of the peppers.


NASA astronaut Shane Kimbrough initiated the experiment on 12 July 2021, and the peppers will grow for 120 days, with astronauts harvesting

the chillis in late October and then again in early November.


NASA is interested in learning how to grow crops in space since fruits and vegetables can supplement astronauts’ diet with key nutrients such as Vitamin C and Vitamin K, which explorers will need during long-duration deep space missions to Mars in the future.


Note: The two controlled-release fertilizers selected by NASA to propagate the chili peppers in the APH on the ISS are: Nutricote® is a registered trademark of JCAM-Agri, Japan. GalXE-ONE® is a registered trademark of J.R.Simplot Boise, Idaho IN addition, Arcillite® is a registered trademark of Profile Products, USA.