Hiya, I used to do like 400+ plants at a time... I'm not familur with Siege rule sets... but may have a couple ideas for ya...
For awhile I grew LOTs on a blue beetle, I would put the plants in bags maybe 10-20 plants each bag. Take a bag out, tend them, put back on beetle. Go to next bag, repeat. Works super easy if you use EC. Thing is you cannot stable the blue beetle with items on him, so you would need a crafter or a dedicated person to sit on him, while not tending plants. I made sure to feed him each day, before tending plants so he wouldn't run off wild on me with all my plants. Also growing plants on a blue beetle, they do not grow each day at server up. But instead it is like 24 hours from the last time you tended your plants. This works well if you are not able to log on daily, or tend to forget to take care of you plants.
Also some plants you can walk thru, others you can not. If growing multiple types of plants, and locking them down, pay attention to which you can or cannot walk thru. Put the non walkables around the edges or in rows where they are not gonna be in your way. If you have poppies dust you can identify large stacks of seeds all at one time. They come in handy for unknown seeds.
If a blue beetle does not work for you on Siege...
You can try stacking your plants. It also helps if you know what type of plant your seed will produce. I usually stacked the plant bowls either 5 or 6 high, all the same type of plant. Then use a house deco tool, raise first one as high as it would go, then raise up the next one etc, leaving as much room as you can between them. When they are still pots, it is very easy to tend, once they turn into plants, it gets a little trickier to be able to pin point each plant to tend, but can be done.
For useing this method, you may want to leave two or more
spaces inbetween the rows. Easiest would actually be to do a row of 5 stacked plants along North wall, and then continue along the west wall if needed. But again shorter rows will work if you leave the spaces between the rows.
I always carried my kegs of potions on me, then I would just step in front of the stack of plants I was tending, when done with that stack, step in front of the next stack and tend to that one etc. It helped to keep from missing plants. I would also keep apples or something in my pack, to be able to drop down or lock down in front of last row or stack of plants that I am tending, in case I had to stop in the middle to grab more potions, or if I got called away from the computer for some reason. That way I would know where I left off.
Stacking plants work well, but could be difficult if you have multiple types of plants all in one stack. It might be hard to see a little flax plant amidst some big ol fat pampass grass.
Feel free to PM me if ya like or have additional questions. Hope some of this helps. Again, I'm not familur with Siege, and I don't know what kind of plants you trying to grow...
Good Luck!!!