An instructor at a Phoenix gardening workshop demonstrated how to start hydroponic seedlings, showing participants how to calibrate and use a pH meter, lower alkaline faucet water to the proper acidity, saturate rock wool plugs and manage humidity and fertilizer before transplanting seedlings to a raft system.

The instructor said, “So we'll walk through how we get the seedlings started and also how we use the the pH meter. So we already calibrated the, the pH meter.” He tested the tap water and reported, “Looks like your water is about 7.7,” then added acid in small amounts and rechecked the solution until “it's about 5, 5.6,” which he described as “right where we wanna be.”

The instructor demonstrated adding phosphoric acid to lower water pH and cautioned participants on safety: “This is the the phosphoric acid, which you definitely wanna keep away from definitely keep away from the kids and the lid.” He said only a “tiny bit” is needed and showed how to mix it with a small volume of water for the seed tray.

He then explained how to prepare rock wool plugs. The instructor described rock wool’s texture and handling: “The rock wool, it sort of has the consistency of dense dense fiberglass. If your skin is sensitive to it, you can just just rinse your hands when you're when you're done or use gloves.” He demonstrated saturating each plug so it made contact with the tray ribs; when the bottom of the rock wool touches the tray it will “wick up the rest of the way.”

On seed placement, the instructor advised using pelleted seeds for ease of handling, especially for tiny seeds such as kale: “With the seeds, the the pelleted seeds, have a little clay coating around them. It helps to protect the seed. It helps to, distribute the the water evenly around the seed.” He showed how to drop the pellet into the hole and, if needed, use tweezers to push it just below the surface so roots do not grow over the top of the rock wool.

After planting, he instructed participants to place the humidity dome over the tray and keep the vents closed until the seeds sprout. “In a couple of days, they're gonna sprout,” he said, and recommended opening the dome vents and putting the seedlings under lights “about a day after those pop.” He warned to cover unused holes on the raft so “the light doesn't get through and start growing the algae.”

The instructor gave a transplant timetable: when seedlings grow until their leaves “start to touch each other,” usually about 10 to 14 days, break each rock wool square apart and plant each into the holes on the raft. On fertilization he advised minimal or no fertilizer while seedlings are in the dome: “When the plants are young, they don't need to be fertilized as much as the full system does.” He recommended mixing a small amount of system water with tap water to dilute fertilizer for seedlings, then moving plants into the full-strength nutrient solution after transplant. He summarized the interim approach as “About halfway,” referring to roughly half-strength feed before transplant.

Participants were told to monitor evaporation once the dome is removed and to adjust water and pH as the young plants grow. The instructor offered follow-up support: “If you're having any kind of issues, please please reach out. Email, call, text, whatever. If I can't figure it out, I'll I'll get to some of the other guys at the park.”

No formal decisions, motions or policy actions were taken during the session; the meeting was an instructional workshop and not a legislative or contracting proceeding.

For attendees: follow safety guidance when handling phosphoric acid, keep humidity domes ventilated once seedlings sprout, cover unused holes to limit algae, expect to transplant in about 10–14 days, and transition from pH-only water to diluted fertilizer and finally to the full nutrient solution after transplant.