I'm playing a cleric with the plant domain, and I'd like to have be able to summon or otherwise have plant allies, but my options seem limited, extremely so at low levels. The options I'm aware of are
Summon monster and summon nature's ally both seem to lack any plants. Are there any options to have plant allies, preferably available to a cleric?
Getting plant allies as a cleric--even if the cleric has the plant Domain--is just not a well supported option in Pathfinder. Summoning them appears impossible, and even making Diplomacy skill checks versus low-Intelligence plants (wild plants?) requires the wild empathy ability then the feat Greater Wild Empathy, and unlike so many things in Pathfinder (like the once class-feature-only ability to use the Disable Device skill to disable magical traps that can now be gotten with a trait) wild empathy is--so far--only ever offered as a class feature, requiring multiclassing into druid or ranger or whatever.
There are only a handful of options, and none of them are what you want, but maybe you can make do.
The spell awaken has been revised and clarified from its D&D 3.5 roots to make the affected creature more like a follower than just a new sentient who digs you. But the spell's not on your spell list.
The Staff of Because Talking Plants Are Awesome
Aura: Transmutation and abjuration; CL: 9th; Slot: None; Price: 12,070 gp; Weight: 5 lbs.
Description: This hollow steel staff depicts clerics in metal armor carrying light steel shields and wielding morningstars beating up sobbing hippies. When used as a weapon, it makes a deeply satisfying hollow clang that seems louder when the victim is a druid. The staff allows use of the following spells:
Construction Requirements: Craft Staff, awaken, shield of faith. Cost: 6,035 gp (Math: ((400 gp x 5 for the spell awaken x 9 for the caster level) + (2,000 gp for material components x 50 to charge the staff) / 10 for 10 charges per use) + ((300 gp x 1 for the spell shield of faith x 9 for the caster level) / 10 for 10 charges per use)).
Note: A cleric can recharge the staff of because talking plants are awesome because of the presence of the shield of faith spell in the staff but must make Use Magic Device skill checks to employ the awaken function. The awaken spell has a 24-hour casting time anyway, so whatever. This staff permits a cleric who has access to 5th-level spells and is willing to commit the resources to being able to use it and recharge it to awaken a plant once every 10 days. You weren't going to use it to cast shield of faith anyway.
The Crown of Bow before Your New Master, Plant Dudes
Aura: Transmutation; CL: 9th; Slot: Head; Price: 36,200 gp; Weight 1 lb.
Description: Once per day on command, this light steel crown depicting moping hermits being evicted from a forest by a valiant metal-armored cleric allows the wearer to spend 24 hours to use the magic of the awaken spell.
Construction Requirements: Craft Wondrous Item, awaken; Cost: 18,100 gp (Math: ((1,800 x 5 for the spell awaken x 9 for the caster level) + (2,000 gp for material components x 50 for an uncharged item)) / 5 for 1 use per day).
Note: The spend 24 hours in the description is not a new requirement but a reminder of the awaken spell's casting time. This has the advantage of being usable by anyone without needing the Use Magic Device skill.
Holt Warden offers the ability to Rebuke Plants.
Holt Warden, the 3.5 PrC (complete champion) is designed for Plant domain clerics. Critically, as its 2nd level special ability, the cleric gains the ability to Rebuke Plants (much like an evil cleric gains Rebuke Undead). While nominally this is not useful to the 3.5 cleric having the plant domain (as the 3.5 plant domain grants rebuke plants) it's much more valuable to the pathfinder cleric.
This answer primarily uses 3.5 rules and is extremely sketchy.
The core of the build is the "Greenbound Summoning" feat from Lost Empires of Faerun. (I do recommend adding the +2 spell level metamagic to it, just ... so it's allowed)
This feat allows any animal you summon to have the greenbound template applied to it, making it a plant. (Maybe refluff the summons into planty summons?)
However, there are no "easy" (or even hard) ways for a pure cleric to get Summon Nature's Ally. The only way that I've found, so far, that isn't restricted to multi-classing bard, or only getting some of the summon nature's ally spells (animal domain) is the Skypledged PrC from Races of the Wild.
The spellpool mechanic allows clerics to summon spells (like Awaken and Summon Nature's Ally) from both the cleric and druid spell lists, which neatly solves all of your problems save for the DM forbidding this method.
Your only real alternative is crafting a Living Topiary (made possible via your plant domain) at 8th level. As a 4 limbed slam attacking... bramble... it seems exceedingly underwhelming.
Leadership offers a monster cohort. If you could find a plant that wasn't atrocious, maybe you could take that?
If you're up for rewriting things, the Undead Lord archetype works very well for you, so long as you replace the word "undead" with "plant". With "corpse companion" and Command Undead (the feat), it does seem like a quite simple remmaping. Since it's a considerable decrease in power, there shouldn't be any problems from your DM.
Hey I Can Chan has given a pretty good answer regarding the options available in Pathfinder, but it’s fairly slim pickings. D&D 3.5 doesn’t have much better, sadly, but here’s what there is.
Requires cleric or druid level 5th, as well as a nature god as a patron deity (the feat actually lists the nature gods of Faerûn in its requirement, but for playing in not-Faerûn, the feat is not specific to any one of them). This feat allows you to rebuke plants as an evil cleric rebukes undead, allowing you to to command a plant-creature army if you can find enough of them. It also lets you rebuke animals, and adds several plant-based spells to your spell list.
If for whatever reason this is unavailable to you, you can take both Plant Defiance and Plant Control to allow you to both turn and rebuke plant creatures. No animals, no extra spells, and it takes two feats, so it’s horribly overpriced, but as SRD material it is accessible.
Leadership can attract creatures as cohorts and followers, so you can get a significant plant creature companion as well as a number of low-level plant creature followers if you desire.
Note that Draconomicon has a feat Dragon Cohort which allows you to get a cohort without Leadership, and that cohort is a dragon-type creature 3 levels higher than you could usually have as a cohort. Swap Dragon for Plant and this could be a good deal. No followers this way though.
Doesn’t have anything to do with plant allies, just makes your more plant-like. Still, a natural armor bonus and fortification isn’t bad for a feat, and it is fitting. Note that Complete Champion allows clerics to trade in a domain for the corresponding devotion feat: this is not required. A cleric with the plant domain can still take plant devotion as a feat.
I was honestly shocked that this was all I could find out of all of 3.5’s prestige classes.
Holt wardens are clerics with the plant domain who join the Guardians of the Green. It’s a prestige class that advances divine spellcasting at every level, and its prerequisites consist of skill ranks you probably want anyway plus being able to cast spells of the Plant Domain, making it pretty painless to take.
As Brian mentioned, this grants the ability to rebuke plants. Initiate of Nature is massively cheaper, and because of its other benefits, is probably worth taking even if you do take levels of holt warden.
Aside from that, you get the ability to spontaneously swap out spells for Plant Domain spells (but this replaces your existing ability to do that with cure or inflict spells), and you get the druid’s Nature Sense, Woodland Stride, Trackless Step, and Timeless Body features. You also get a 1/day, 10-minute-casting-time heal spell, quite a bit earlier than the real thing becomes available, which is nice enough. Immunity to venom, various divination-through-the-forest rituals, and the ability to give all living creatures who hear you +2 Wisdom and restore some spells to divine spellcasters.
Ultimately, it’s OK, but not great. Becomes much better if Initiate of Nature is unavailable.
These are things you cannot reasonably get as a cleric, even in 3.5, but might be viable for porting to Pathfinder as feats or an archetype.
This class feature, found on the arcane hierophant prestige class, allows you to cast spells from any non-magical, non-creature plant. Considering that the previous feature, Channel Animals, allowed you to do the same from any animal creature, extending this to plant creatures would be reasonable enough (in fact, considering their usual rarity, casting from plant creatures is inferior to casting from any non-creature plant).
I mention this feat only because it is fantastically powerful. It is extremely difficult for cleric to qualify for it and it is inappropriate in most games. It does, however, allow you to have powerful plant summons. As part of an archetype that adds summon nature’s ally to your cleric list, perhaps, it might work? I’d either delay it until ~10th level or greatly modify the greenbound template, though.
This honestly seems like the type of things where you just need to go into Summon Nature's Ally and add some reasonable plant equivalents. It will probably take some time because we have a lot less animated plants than we do creatures, but hey, we get to create stuff right?
