how to use thavnairian onion

FFXIV Chocobo

Thavnairian onions are the most important vegetable in Final Fantasy XIV. Your chocobo is your best ally when completing quests, running FATEs, or killing hunt mobs. It's in your best interest to max out his level as quickly as possible so that you always have a pocket tank, a pocket healer, or a little extra damage while you're in the open world. You'll need to feed your chocobo one of these onions every time they level past 10. Since chocobos max out at level 20, you'll need a total of 10 to complete your chocobo's progress.

Getting Thavnairian onions can be a tiresome task. Many Free Companies grow onions in bulk for their members, since spreading the burden of planting and watering across multiple gardeners makes it substantially easier. But an industrious gardener can certainly grow them alone.

Using Thavnairian onions

Once your choco-buddy hits level 10, they stop gaining experience points. Feed your chocobo an onion, either while he's stabled or in the open world, and they'll be able to gain the experience points needed to hit level 11.

Thavnairian onions as quest rewards

There are two quests that award Thavnairian onions:

Landing a Stable Job: Once you've completed the Level 50 Main Scenario Quest 'The Better Half,' it unlocks an Ishgardian sidequest called Landing A Stable Job. Pick it up in The Jeweled Crozier (X: 6, Y:9) from Mathye.
A Hunter's True Nature: This quest has a few pre-requisites. You'll need to have completed 3 sidequests in the Dravanian Forelands: 'Pest Control,' 'A Step in the Right Direction,' and 'Garbage Duty.' Once you've done those three, visit Hervoix in Tailfeather (X: 32, Y:23) to pick this quest up and get your onion.

Growing Thavnairian onions

Growing your own Thavnairian onions is a labor of love that can take weeks. You can either purchase Thavnairian onion seeds from the marketboard and grow them yourself, or cross-breed other common plants to obtain the seeds. Thavnairian onion seeds take 10 days to grow. If you cross-breed to get the seeds, expect to spend an extra 5 to 6 days waiting for your crosses to sprout.

The easiest method we've found is as follows:

Cross-breed Krakka Root and Mirror Apple to get Curiel Root.
Cross-breed Almonds and Mandrakes to get Nymeia Lillies.
Then, cross-breed the Curiel Root and Nymeia Lillies to have a chance of getting Thavnairian onion seeds.
Plant your onion seeds

There are a number of other potential crossbreeds that will yield Thavnairian onion seeds listed on the FFXIV Gardening site.