A few years ago I bought a lot of seeds from Mesa Garden in Belen, NM. My health issues stopped me from planting any of the seeds. I felt up to it this year, so I planted all the seeds in January and February. The seeds were germinated under 4' (122 cm) LED lights, bought at Costco. I did the experiment a few years back comparing the then-new LED lights vs the older standby of fluorescents. I saw no significant difference in plant growth, with maybe better growth under the LEDs. The big difference was the waste heat. I had to buy an air conditioner for my growing room. The LEDs get warm, but not hot, so no AC is needed. The AC has been stored in the garage, but it found a use last summer, cooling our bedroom. I never felt like I needed AC to live in Los Alamos, but global warming is real. My garden says so.
You're looking at 14 10 X 20 nursery trays, each tray having 32 cells. This is a total of 448 cells. Each cell had at least 100 seeds sown in it. This is 44,800 seeds. I had good luck with germination and propagation. I only lost one cell of plants due to a fungus attack, and my overall germination rate was easily over 50%. This means that you're looking at about 44,800 X 0.50 = 22,400 cactus plants. Maybe you can understand how quickly one can acquire thousands of plants. On Jan 1, 2020 those trays were empty. In mid-June 2020 they contain 22,400 plants. You can see that some of the cells appear to contain wall-to-wall plants. Those cells contain from 80 to 100 plants. Unhindered growth is exponential. (You have been paying attention to the coronavirus outbreak, no?) Those 22,400 cacti now occupy roughly 28 square feet of space. This is 4032 square inches. My greenhouse is 22 feet X 14 feet. The two cloches are 22 feet X 3 feet and 22 feet X 6 feet. So my total enclosed space is 22 feet X 23 feet = 506 square feet = (x144 sq in/1 sq ft) = 72,864 square inches. If I were to move the 22,400 cactus seedlings evenly into this space, each plant would be allocated 72,864 square inches divided by 22,400 cacti = 3.25 square inches per plant. I can grow a cactus the size of a tennis ball, easily, given 3.25 square inches of sun space. The size of the plant would also be governed by the volume of the pot. This little math exercise is meant to convince you that it's possible that I may have very many thousands of plants. This one picture has an estimated 22,400 plants. To your natural question of why would I want so many plants, I have no answer. I like to watch them grow, especially starting with a seed. (8/8)