A fixed number of Red Iris Flowers spawn when you enter an Explorable Area; they can be picked up by any party member. They are plentiful in Pre-Searing Ascalon and somewhat harder to find elsewhere. Each Iris appears randomly within a smaller dropzone of the area, so the flowers can be easy to find once you identify those dropzones.
2 irises spawn in Gwen's Garden on the west side of the Eye of the North. Exit the outpost and follow the wall around to the right. This is by far the easiest way to get irises: there are no foes to deal with on the way, so the only skills needed are running skills to speed runs up.
To obtain a Tapestry Shred, you must give Gwen at least one iris after you have obtained her favor.
To trigger the From the Past dialogue, you must have an Iris (or other Gwen-related item) before speaking with Gwen in the Hall of Monuments.
The quickest place to farm irises in pre-searing is in Lakeside County; you can find the 5 flowers there in less than 5 minutes, if you ignore the mobs. Or you can simply map-travel to Ashford Abbey, walk out, grab the flower on the right (there's always one), and repeat; 1 flower every 36.24 seconds = 99 flowers per hour. Outside of pre-Searing, you can grab the two irises in Gwen's Garden in less than 2 minutes.
An alternate location is to travel North from Foibles Fair. Look to the west as you go up the path one is usually visible; then head east then south through bear country towards the river to find another then map back to Foibles Fair. A bit less than 1 hour to collect 50 flowers.
To make it easier to find irises, add a keyboard shortcut to Target Next Item and spam that key when you get close to the iris-spawning part of a zone. Alternatively, using the default keys, keep the [Alt] key pressed as you explore and frequently change the direction you are facing.
To add a keyboard shortcut, open the Options window (default key: [F11]), switch to the Controls tab, find the command, Target Next Item, press a key (e.g. [PageDown]), and click on the assign button.
Bug! The 23 April 2009 update was meant to fix a bug causing Red Iris Flowers to drop in Pre-Searing Ascalon with much less frequency than originally intended. However, the frequency appears to be unchanged since the update. Instead, the flowers are significantly easier to find.
Some players consider the flowers to be worth 50 in pre-Searing because the local cost of the the Small Equipment Pack is 50 flowers and the Post merchant price is 2 500 . However, others point out that, strictly speaking, money and items can only travel out of pre-Searing and the price comparisons should be irrelevant.
Historical note: Prior to the 9 April 2009 update, there were no collectors for Irises and they were only valuable to merchants or to convert to Tapestry Shreds.
Historical note: Prior to the 23 April 2009 update, Irises were much harder to find. Rather than spawning on entry into a zone, they dropped only when you approached their location within aggro distance. Since the update, they can be found easily by targeting others (default key: [alt]) or targeting next item (no default key).