Consider using [mwcard=MWSTX2FFW01]Wall of Earth[/mwcard].
Keep in mind that if he tries to burn down your tree it will likely get telegraphed early. There are ways to protect it, but every mage but the warlord has to actually damage it to kill it n that means he is likely to believe that 16 mana and 2 actions is going to be worth the investment. He's wrong. Use that to your advantage, he has to get within 3 (with dragons breath or hurl meteorite, and he only gets one of those a turn) most likely 2 to throw his fiery balls of death and your home zone is a tough place to get to after a few vines show up. Early tanglevine can gain you an action or two to get ahead, or at least force a teleport or a lash of hellfire (can't use ranged attacks so no fireballs or blasts).
If he tries to bring down your tree, make him pay for it.
Single [mwcard=MW1A04]Fireball[/mwcard] can take down [mwcard=DRUIDABILITYOUTLINE]Treebonded[/mwcard] [mwcard=DNJ12]Vine Tree[/mwcard]. Even without telegraphing it the Warlock can get into range 2 in second round:
Round 1: crystal, move + Forge
Round 2: double move + fireball
If he's lucky then You're without the tree.
What You need to do is to prevent him getting into range or from targeting the tree. Even after running to NC after dropping the Tree You will not be able to hinder the Warlock with vines only. You may want to cast [mwcard=MWSTX2FFW01]Wall of Earth[/mwcard] in such place that he either has to take down it, or step into vines, or go around. I prefer Wall of Earth over Tanglevine for few reasons. It's more permanent against Warlock (and if it's female Warlock that runs only demons without non-flame attacks (like [mwcard=MW1C01]Adramelech[/mwcard]) then You may trap her for good). You need to be in NC before the Warlock can act in round 2 to cast Tanglevine on him (but even then You may not be able to do so if he gets obscured somehow), there's no such need with the wall if You're willing to spend more mana.
More aggressive opening for Warlock could be:
Round 1: Hawkeye/Fireshaper Ring, move + Cheetah's Speed
Round 2: double move + either 2x fireball or Akiro's Favor + Fireball
It's telegraphed for sure, but if You won't be in NC to tanglevine him before he can act in second round then he will be able to pull it off. With the wall You may either run to NC in first round, spread vines to FC and cast wall in second round, or stay where You want and cast extended wall.
Wall may also prevent the Warlock from teleporting himself in attack range.
Other option include casting [mwcard=MWSTX2FFJ06]Rolling Fog[/mwcard] or summoning a creature that can intercept attacks. This should give You enough time to setup Wall of Thorns and push him trough it once or twice.
Let's not forget that not all Warlocks are pyromaniacs and they have access to most of the nasty tricks a Necromancer can use. Dropping both [mwcard=MW1J11]Idol of Pestilence[/mwcard] and [mwcard=MW1J19]Deathlock[/mwcard] after summoning [mwcard=DNC22]Zombie Brute[/mwcard] or two is possible for Warlock.
Cervere or Galador with Lion Savagery/Bear Strength are good options to deal with such threat, but have some seeking dispels prepared to destroy [mwcard=DNE02]Rise Again[/mwcard] or You will have to deal with zombie animals.
