I am puzzled by the fact that some of my tulips return year after year, while others just peter out. I planted the oldest ones, deep red tulips, over 20 years ago. After about 10 years of them enjoying the "price" spot in our garden,I decided to turn this place into an herb garden. We dug up all the soil, sifted through it and removed all large and small bulbs, and replanted them in an area that is less sunny. They keep blooming there every year, but in the herb garden we have more tulips than ever before! The tiniest bulbs obviously sneeked by us. And I let them win!

Now to my problem: about 8 years ago I planted tulip bulbs for beautiful pink/lilac long stem late blooming tulips, and some purple ones with a bit shorter stems; they get morning sun until they are shaded by a fence. They bloomed gorgeously for a couple of years, then started to peter out, (in spite of fertilizing them the same as other tulips I have in other areas of the garden..) For the last few years these only produced leaves. In fact they are in leaves now, no stems in sight.

Is it that some bulbs are just longer lasting than others? Or is the shade the problem? Or, as someone suggested, bulbs move deeper over time and need to be dug up and re-planted at the appropriate depth?

Would it be worth my while to dig up all non producing bulbs once the leaves have yellowed, and then dig them in again, but in an area that is sunnier? Or would I be wasting my time?

Would love to hear from people in the know!