I made this Anchor Weed farming guide to help out players who want to farm the herbs instead of buying them from the Auction House. You can pick Anchor Weed with BfA Herbalism skill 1, but the rank 2 and rank 3 requires higher Herbalism skill. Higher ranks allow you to gather this herb more effectively, so you will get more herbs overall.
Anchor Weed is a rare herb that can sometimes spawn instead of other herbs. So basically if you want to farm Anchor Weed, you have to farm other Herbs and hope they will respawn as Anchor Weed.
Anchor Weed
Anchor Weed ranks
You will learn rank 1 from your Herbalism trainer at Daz'Alor / Boralus after you reach Herbalism 25.
Rank 2 is a reward from 
Seeking More Knowledge. This quest unlocks at BfA Herbalism 115, and is given to you by your Herbalism trainer at Daz'Alor / Boralus.
Rank 3 is a reward from More Anchor Pods. You can get this quest after you loot one 
[Enormous Anchor Pod] while gathering Anchor Weed. It's not 100% drop, and you will need Herbalism 150 before you can pick up the quest. (the quest item can drop at lower herbalism skill)
How to speed up farming
Battle for Azeroth introduces three new items that you can use to speed up farming herbs. You should use these if you can find them cheap at the Auction House, or craft it yourself if you can.
[Monel-Hardened Stirrups] - You can gather while mounted.
[Monel-Hardened Hoofplates] - Increase mount speed by 20%.
[Coarse Leather Barding] - Prevents you from being dazed. (mobs won't dismount you)
The one I would recommend the most is [Monel-Hardened Stirrups], which lets you gather herbs while mounted. Every mob scales to your level in Battle for Azeroth, so it will be hard to avoid the mobs attacking you while you try to farm herbs. If you have the 
[Sky Golem] mount, you can use that instead of the Monel-Hardened Stirrups
If your class has a tanking spec, you should switch to that while farming, so you won't get dazed and you don't have to use Coarse Leather Barding.
Don't forget to enchant your gloves with 
[Enchant Gloves - Zandalari Herbalism] or [Enchant Gloves - Kul Tiran Herbalism]! This enchant brings gathering time down from 1.5 seconds to 0.5 seconds. This is really important if you gather while mounted because mobs can still interrupt your casting.
Drustvar - route 1
Since Anchor Weed is a rare herb that can sometimes spawn instead of other herbs. This route is the best because it has the most herbs, so you will have more chances of getting Anchor Weed.
This route goes through an Alliance town, so horde players might have some trouble here, but you can just run past the guards with mount, they shouldn't kill you.
Drustvar - route 2
Use this route if someone is already farming at the first route, or if you are having trouble going through the Alliance town.
Tiragarde Sound
This is also the best place to farm Riverbud.
Stormsong Valley
You will get a lot of Riverbud and Sea Stalk here. Really good route, since you can avoid fighting most mobs.
Nazmir
You will get mostly Siren's Pollen and Riverbud here.
