There are a total of 10 seeds to find: 2 on Bogano, 3 on Zeffo, 3 on Kashyyyk and 2 on Dathomir. The seeds can be obtained by having BD-1 scan the flower/plant they are for.
The order of the plants in the terrarium is as follows:
Featherfern - Bogano, Fractured Plain. It’s a high, grassy plant with a purple flower. Can be found just over the broken metal bridge from the area with 3 holes in the floor (Above where Oggdo Bogdo resides)
Kalpi - Bogano, Subterranean Refuge. From the Meditation spot at the bottom of the big round chamber, facing inwards look down to the right and you should see it in the water next to a pile of rubble and a Bog Rat.
Dreamwort - Zeffo, Crash Site. As you exit the cave where the save point is, head across the water and past the round part of the wreck. You’ll find a tiny yellow flower on the shore near the tower.
Royal Fluzz - Zeffo, Weathered Monument. From the Meditation spot in the valley cross the stone bridge past the Heavy Assault Trooper and into the cave. Cross the pipes and the pass the second Heavy Assault Trooper to the ledge in front. Immediately turn left to where the chest is surrounded by purple flowers and scan the glowy one for the seed.
Gillypod - Zeffo, Windswept Ruins Atop a stone column near the save point. Use the hot air blasting from the floor to get on top of the pillar, then scan the red flower to get the seed.
Milk Grass - Kashyyyk, Gloomroot Hollow From the Meditation spot Head through the cave with the Flame Beetles till you reach a path covered with Jaw Plants. Turn left as soon as possible and climb onto the ledge, then turn around and you will see the plant.
Mushbloom - Kashyyyk, The Origin Tree When you reach the meditation spot, climb up the ledge and head under the stone ramp. You should see a plant in the distance the seed can be obtained from there.
Bonshyyyr - Kashyyyk, Imperial Refinery From the meditation spot in front of where the Storm Troopers are fighting the Wyyyschokk's The flower can be found on the battlefield but it can be tricky to spot due to its small size.
Bleeding Gut - Dathomir, Swamp of Sacrifice From the meditation spot, jump down to the bottom and head towards the red vine. Follow the path past it until you spot a big dark red flower in the corner.
Mushling - Dathomir, Swamp of Sacrifice At the bottom of the swamp in the area with the big tree with Nightsister pods hanging from it. The seed can be found at the base of the cliff next to the tree