One of the strongest Plant-Type monsters is "Tytannial, Princess of Camellias" at 2800 ATK. It has the power to negate any card effects that target simply by sacrificing a Plant-Type monster (which in worst case scenario can even be herself). It can be easily Summoned by Tributing "Lonefire Blossom". In power and strategy, "Tytannial, Princess of Camellias" is followed by "Gigaplant", which has 2400 ATK and the power to Special Summon Plants from the Graveyard and hand.
The most usual Attributes associated with Plants is EARTH or WATER. Plant cards usually revolve around swarming and regenerating back onto the field. Unlike Zombies, Plants are often used to fuel effects such as negations rather than for strictly attacking purposes. They have many cards that allow them to be special summoned to the field from the deck and hand but mostly from the Graveyard. Cards like "Lonefire Blossom", "Plant Food Chain", "Lord Poison", "Gigaplant", "The World Tree" and "Miracle Fertilizer" all add major support to bringing back a swarm of Plant monsters to overwhelm the opponent. There are many good Plant-Type Tuner monsters, like "Copy Plant" and "Spore".
This deck revolves around "Lonefire Blossom" and "Gigaplant" to help swarm the field. Make sure you use the effect of "Gigaplant" effectively in order to pull decent Synchro Monsters out while using "Queen of Thorns" to make your opponent pay life points to summon non-plant monsters. You could use "Tytannial, Princess of Camellias" and combo it with "Gigaplant" so you could tribute Plant monsters Special Summoned by "Gigaplant"'s effect to negate any cards that target your plant monsters. You can also keep the opponent at bay with powerful cards like "Wall of Thorns". This deck also uses "Pollinosis" or "Tytannial, Princess of Camellias" to negate Spells and Traps that destroy multiple monsters such as "Lightning Vortex" or "Mirror Force" or "Torrential Tribute", however, this can be entirely foiled with cards like "Zombie World" and "DNA Surgery", so be sure to pack in "Mystical Space Typhoon". This deck's ability to swarm the field quickly for fuel or for an all out attack can be foiled by cards like these.
This is a deck utilizing "Supervise" and "Hidden Armory" which allows players to Synchro Summon quickly with the main monsters "Gigaplant" and "Spore". This can Summon a variety of different Synchros to control the field, but most used is "Power Tool Dragon", which allows the player to grab a quick "Supervise".
The successor to the very popular Plant Synchro deck, Chaos Plants takes advantage of the LIGHT and DARK attributes of splashable monsters, such as "Sangan" and "Effect Veiler", to Summon "Black Luster Soldier - Envoy of the Beginning", in combination with the Synchro abilities of Plants. It rarely uses enough Lights and Darks for it to be worth using "Chaos Sorcerer". Something to note is that it despite being called a "Plant" Deck, it often uses more Fiend monsters than Plants.