Buckwheat question

I planted a cover crop mix of Buckwheat, Oats, Daikon Radish, Globe radish,  and Snap peas into to beds I plan on using as an herb garden in the spring.   Everything has come up pretty well but the buckwheat is only about 12inches tall and is already flowering!  Is this normal?  I was expecting at least twice that much growth from it but it appears the buckwheat had other ideas.  I'll probably let it flower for a week then cut the whole mix down and reseed with 90% oats and some snap peas for the winter.  Was hoping to get another month of this crop but letting the buckwheat go to seed isn't a good idea at this time.

It sounds normal. Buckwheat flowers quickly. Mine grows taller in the summer than in the fall. The last batch planted this year are finishing up now & they are only about a foot tall. The ones in summer were 2 or 3 feet tall. My guess is the difference is due to different day lengths.

Sounds normal for me

Thank you for the responses!  It is flowering well now so I'm guessing my expectations of how tall it would grow were what was wrong not the plants themselves  I've decided not to cut down the cover crop and just let the buckwheat reseed itself if it wants to.  The people who lived here before me decided to use masses of landscape fabric in what I thought was a raised bed but now am thinking was just a 'picnic' area.   I didn't know this when I planted into it but rather when I went to make 3 more beds I found the offending fabric.  Instead of ripping it up I'm just going to use the area as a wood mulch composting zone with the exception of the 2 beds already in it.  Those beds I'll plant herbs into-mostly annuals but also some mints that should do well in partial shade and hopefully be mostly contained by the fabric+wood chips all around them.