You can hammer in a couple of stakes and run a string around the fern. The more top growth they have the stronger the plants will grow and the better your asparagus crop.

^^^ that's exactly what I do. I put a 4' piece of re-bar in each corner of my raised beds and run twine around the stakes every foot or so.

That's what I thought but just wanted to check.

How many years did you wait before you took your first harvest?

I planted 2 year old crowns every time and took a small 2 week long harvest the second year and then increased the harvest by a week or 2 each year until I got to about 2 months. You just need to evaluate how the crowns are producing and when most of the spears are smaller than a pencil it's best to stop harvesting.

That being said, I'll usually have some crowns that I can harvest longer than others. You want them to have enough energy left to produce enough large spears/ferns to recharge the crowns for the next season.

Fertilizing is important. I fertilize 3 or 4 times a year. Once in late winter before the spears start to come up, once after harvest is finished, sometime in August, and again in mid fall before the soil freezes up.