I would ratchet up the magical effects bit by bit.
In my magical system, increasing vital, organic, frondescence would have effects like the tree you mention.
I picture an enormous 'Dracaena cinnabari'
The following is all based on my homebrew.
In my cosmology the Dragon Tree is associated with 3 essences of growth, wildfire and venom so I would flavor my effects along those themes.
Rapid plant growth - a blooming desert.
Epiphany delivered to sleepers and sages.
Roots upsetting walls and structures
Canopy joining roofs across streets
High spirits and spreading romance
Red ivy spreading up walls and trees
Bonfires spontaneously igniting and spreading
People pursuing religion with zeal and conviction
Feelings of infinite possibility and potential
Yellowing stone and plants
Venomous creatures spreading and swarming
Corruption of water and foodstuff
Bile fouling wells and sickening people
Predation and attacks on the weak and needy
There would also be weather & environmental effects/traps, based on elements of light, fire, earth and life:
Desert Blindness
Hot Snaps
Extreme Heat
Sunburn
Poison Gasses
Mold Growth
Hunger Fields
Ravenous Insect Swarms
Fairy Circles
Flowering Desert
Sandstorms
Smoke Clouds
Dry Spell
Chasms Open
For planar portals, I would expect them to open to the Feywild and Abyss.
Hope this all helps for inspiration, good luck!