Flax = Linen. That's important to understand. Just as Cows = Beef and Pigs = Bacon. Flax is the plant that gives us flax seed, flax seed oil, linseed oil and flax fiber. Because there are several products possible from flax, it shouldn't be any surprise that there are many plant varients. Flax grown for seed/oil is often short and branchy while the flax grown for fiber is tall and slender with small leaves. The plants are traditionally grown very closely spaced so at harvest time there is a carpet of 3' tall plants with heavy seed heads. The flowers are blue or red or white or yellow depending on the varient. The close spacing lets the individual plants literally lean on their neighbors to remain upright, particularly imporatant as the seed heads mature and get heavier. It also doesn't let weeds get a foothold.
Flax takes large amounts of neutrients from the soil so when it is grown in the same fields year after year the ground must be fertilized. Historically, flax was grown in lowlands that were flooded by the sea during parts of the year. This added the needed nutrients. The other obvious tack is to add manure.
To get the long fine flax fibers a spinner would want requires just the correct amount of heat, length of day and amount of rain. I bought some seeds several years back that I intend on planting this coming spring. I have heard that there is too much heat and not enough rain here for excellent long line flax but it's worth a try to see what I get. Processing flax to the point that it's ready to spin into linen yarn has lots of steps and requires lots of manual labor. I doubt I could handle an acre of flax but I think a single 7' diameter garden bin ought to be within my capabilities.
So flax is grown, pulled up by the roots, wetted to help rot off the outer and inner portions of the stem, then dried and broken and combed so that it finally can be twisted into a fine flax strick. The strick is a convenient twisted bundle that was bought and sold, traded and used. The strick is the finest of long line flax but not the only product. Also created in the process is tow flax, the shorter fibers not long enough to be included in the strick.
Flax strick can be spun into very fine, very thin linen yarn. The tow linen is also spun but makes a less smooth, more hairy yarn. The longer fibers are also cut or chopped into a shorter length to make roving or combed top for a different spinning experience and for easier blending with other fibers. I have tried the roving and top and while some is much better than others, my favorite to spin is the strick.
More about the spinning later.