Growing the GardensFebruary 1, 2024
Discover The Living Desert’s new, behind-the-scenes propagation greenhouse and garden with Plant Propagator Jose Marfori. Construction on the propagation garden and greenhouse began in January 2022 and the gardening team is still in the process of completing the nursery. The greenhouse measures 20 feet by 60 feet, and the entire nursery is just under 0.7 acres of space.
What types of plants are you currently propagating?
We propagate different types of plants from different areas, in addition to California native plants. Most plants are predictably from arid areas across the globe, but some are also native to moist, tropical locations and still do well in our hot, dry climate.
Do you propagate food plants here that the animals will eventually eat?
Yes! For short term needs, we typically buy browse trees at larger sizes (24-inch to 48-inch tree boxes) and let them grow out a bit more or plant them in the browse farm. Looking toward the future, I’ve just started several species of acacia in the greenhouse that will eventually be used as browse for the rhinos, though not for a few years.
Can you talk about the propagation cycle within the nursery?
The start of the propagation process is to collect the propagules. These are most commonly seeds we collect from the Zoo grounds or the field, but we also buy in seeds of plants we wish to add to our living collection. Additionally, we collect cuttings from plants on grounds.
As plants get bigger and placed in bigger pots, they move through the nursery. Seedlings and cuttings stay in the greenhouse in flats and 2-inch pots. At 4 inches, they can go outside if it’s fall to spring but stay in during the summer. 1-gallon pots go under the shade structures outside on the tables. They are watered by sprinklers because installing drip irrigation for that many pots is not feasible or efficient. Pots larger than that are arranged in rows out of the shade and hooked up to drip irrigation.
About how many plants do you have growing at a time in the greenhouse and garden?
Because the nursery is still under construction, our inventory is much less than it could be. For the mid-year inventory of 2023, we had only 3,845 plants growing at the nursery. In 2022, it was 5,920 plants. And in 2021 when I started, we were growing 5,478.
Each of the three tables in the greenhouse can hold 4,650 individual 2-inch pots. Our goal is to be close to that capacity, especially during prime propagating seasons such as fall and spring. That’s not counting the amount of space we can fill up with 1-gallon pots on the tables outside. It’ll probably be close to over 6,000 1-gallon plants! We also have space for at least 100 boxed trees that are for both animal browse and display on grounds.
What different types of propagating are you doing?
Most seeds are easy and the only thing you need to do is sow them on top of soil, cover them, and keep them moist. Some seeds require pretreatment in order to get them to germinate. Some species, like junipers, need their seeds to go through months-long periods of cold temperatures before germinating. We can simulate these conditions by putting seeds in a moist bag of sterile medium and putting it in the fridge, typically for 3 months, before sowing in the greenhouse. Other seeds, like bush poppies, require high temperatures or even fire! For these species, we sow the seeds in a tray and then cover it with a generous layer of pine needles or
chamise before setting it alight! The high temperatures and the chemicals released from the burn stimulate the seeds to germinate.
We also collect cuttings from many plants on grounds, especially when the gardeners are already pruning them for maintenance or when they have special requests for certain areas. Cuttings are more time-consuming but relatively easy for many plants. Cuttings are most useful for propagating plants that don’t reliably produce seeds or when we want to clone specific plants for their characteristics. Individual cuttings are typically 3 to 5 inches. Leaves from the lower half of each cutting are removed and bundles of cuttings are placed in a sanitizing solution to remove pathogens. They are then dipped in rooting hormone before being placed in a tray of perlite. The cuttings are kept in the greenhouse under misters. Cuttings can only absorb water through their leaves until their roots grow, which is why it’s important to keep them moist. Once roots start to grow to the bottom of the tray,
it’s time to pot them up into soil in 2” pots.
Other ways to propagate plants are to divide them. Grasses can be physically divided like a pie and will fill in the space of their new pots. Some bulbs/corms produce offsets underground that can be dug up and planted separately. Some succulents like kalanchoe species produce offsets on their leaves which can be removed and planted directly in soil.
Do you have any tips for home propagation in our climate?
Depends on what you want to grow and how big or small the set up will be. There’s no one size fits all advice. What vegetable seeds will need aren’t necessarily what wildflower seeds will need. Many houseplants don’t need rooting hormone when you take cuttings but many other species do.
But don’t be afraid to experiment! The only way to get better at not killing plants is to kill a lot of them! Every nurseryman and green thumb gardener will tell you that. One thing that has stuck with me though is something a previous manager told me. “The best thing for your plants is your own shadow.” It means that consistent attention will give your plants the best shot at life because you’ll be able to spot if something is wrong right away.
What benefits have you already seen from having the propagation greenhouse and garden?
When the greenhouse was built, we were able to limit our summer losses. This was especially true for many of our tender succulents and certain specimen plants.
What’s next for the nursery?
We just finished installing a third of the shade cloths we need, and now we need to rearrange our tables to go under the shade cloths and start populating the tables with plants! We would also like to start more collaborations with other botanical institutions to exchange plant genetic materials to bolster each other’s conservation efforts.