How deep did you plant them? Have they been fertilized at all?

I planted about 6 inches deep in a compost bed. Fertilized with 10-10-10 mix. have 1 new growth come up the other day but is still very thin.

Yes, more should come up. I think they just naturally vary in thickness. I'm starting my 4th year with asparagus, so I'm not an expert. What surprised me with mine is that I seem to get a few random spears in the late summer too. I eat the thick ones and let the thin ones fern, whatever the time of year.

If they are 3 years and still "thin" - which is subjective - then they haven't been fed enough. You can't count on the compost to supply sufficient nutrients unless there is a very active soil micro-herd in that bed so 2-3 supplemental feedings per year are needed - early spring before any spears, mid-summer, and again in late fall after they go dormant. If you want to use only organics then use composted manures..

Plus depending on how much compost was in the bed, the crown will be exposed as the compost decomposes and you will need to keep topping off the bed with more soil and compost.

If all the new growth you get remians pencil thin then just let them fern this year and don't harvest. With adequate feeding and consistent watering throughout the summer (they need lots of water) next year should be much improved.

Dave

I started Asparagus from seedlings rather than crown roots and it took me a good 4 years before they started to thicken a little, then actually 5 years before they were as fat as I was expecting. I didn't do anything but keep adding compost and ground up leaves. I also let mine fern every year.

I've only used home made compost on mine and they are thick as my thumb for the most part.And plentiful! From a 4x8 bed, the 3 of us eat gus about 2x per week.
I do have clay soil, so possibly more nutrients than some.
Nancy