Knitting is basically two stitches, knit and purl. There are some patterns that are all garter stitch (all knits), but the majority use a combination of both so yes, I'd say you should learn to purl.
**Please provide a pattern link and/or name if possible when asking questions. It's also okay to post a few lines of the pattern, but please don't post the whole pattern.
Yes, unless you plan on doing nothing but garter stitch for the rest of your knitting days.
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Zina
OTN: Eyelet Chemise in Handmaiden Sea Silk (colorway: Midnight). Still. And a purple Donegal Tweed set of fingerless mitts, to try out my new Hiya Hiya interchangeable needles.
Latest FO: A shrug for an Anthropologie swap in beautiful Casbah sock yarn, in Cedar, a dark green semi-solid, my own pattern. Also a quick Noro Silk Garden neckwarmer for my friend Aideen, in a vine lace pattern.
Check out my photoblog: Photobella
Well, I've wrestled with reality for 35 years, Doctor, and I'm happy to state I finally won out over it.
--Elwood P. Dodd