Hiya, I need some help. 3 years ago I bought 5 Jersey Knight Asparagus Crowns. I planted them according to directions,adding compost to my clayish soil, and the next spring they came up nicely. I didn't harvest, since you are supposed to wait til the 2nd year. The next year they came up great! I took a modest harvest and then let them grow back and get fern-y to get energy for next year. I Love fresh asparagus, so I was so excited about this years harvest. So, this year they are coming up so skinny and sparse. Last fall i laid a 1 1/2 inch top layer of compost. I do not have any disease evidence, no insect trouble. I thought it would just get better and better, more productiveas time passed. A tree is filling out near it, and it is going to get a little bit of dappled shade this summer. I haven't used any fertilizers,chemicals,etc except some compost or manure tea once in the summer. Why is my asparagus so wimpy? Does it need something? It tastes great, but these are not even pencil size, except for here and there one thicker stalk will come up. HeLP, Please! I really miss my 'spare a kiss.!
If you get winter freezes, they may have been damaged by that. I mulch my bed after the first killing frost in the fall. I add compost at that time just before mulching. Then remove the mulch early April. Be sure they stay moist but not soggy through the summer, and let them all go to fern after mid July. Seems to work out best for me that way
How many hours of light is that tree blocking? Asparagus definitely prefers all of the sun it can get.
Feed those plants this year! Top dressing with a good compost is a great start, but a wet winter can leach out and wash away much of the nutrients in a fall compost top dressing.
Asparagus doesn't always send up all of it's shoots in the spring, you may see some spears erupt on into the summer if the plants decide they needs to do so, mine often do that.
If you've taken care of fertilizing, full sun and enough water, the next thing I'd suspect is the crowns migrating up toward the surface. Most plants that age should have some thin (pencil -) and some thick (thumb +) stalks. If the crowns reach the surface or get close they seem to put out thinner spears and also tend to get damaged in the winter. Gently check to see how deep the crowns are now, it's easy enough to add a bit of soil/compost over the top. I like to keep them about 3" below the surface.