I am raising broccoli rabe in Zone 5, in Bellbrook OH. The soil is in a raised bed, which is a combination of our local clay amended with manure, compost, and Miracle Grow Organic Topsoil and aged one year over winter. Our temperature has been mostly 65-75F daily, with an occasional day of 80-82F. Rainfall has been 1" - 2" per week, once a week. The rabe appeared to grow well, and is 4 weeks old (30 days). The rabe is planted next to peas and a chive plant. The peas provide some dappled shade at the hottest part of the day to the rabe.
At 4 weeks, I tried some of the rabe, washed thoroughly with 10/1 ratio of water to vinegar, then rinsed with clear water 3 times. I tried both stir frying and steaming these greens, and although they are young, the thin stems are very stringy and woody and extremely bitter, so bitter I spit out the one bite I had tasted. There were no buds or blooms forming yet on these plants, so I think the problem may be in our soil. The broccoli rabe I have purchased at the store is very tender and sweet with a slight touch of bitterness and has stems twice as thick as what my homegrown rabe has. I need to know how to grow rabe that is sweeter and more tender, and how our soil or temperature may have affected the taste of the greens. Any help would be greatly appreciated.