I think the lasagna method was adopted primarily for pot culture...to get longevity of bloom from a single container...and so, it is easy to upend the entire pot and pick through the bulbs. In the open ground, no disturbance is needed. If tulips re-appear the following spring, and are less than stellar, simply pull the entire plant. The crocus will have bloomed and died back so will not be unduly disturbed by soil movements caused by removal of unwanted bulbs.

I agree with all that Camp says and add that some tulips can come back. The Darwin and species types have been successful for others here.

Good idea of Camp's just to pull out the non-performers! I agree that in a well soaked ground (if you have clay like me that won't let anything go otherwise), you can give a plant a wiggle while pulling gently upwards and with patience and wiggling, it should come out. If the bulb is down far enough, I sometimes need a thin trowel to dig down close to the bulb and loosen things out while pulling. I kind of wiggle the trowel around while pulling on the foliage (and wiggling the foliage as well!) For daffodils that are half a foot down - forget it - I have to dig a huge chunk of dirt out and pry them out as the foliage just breaks off if I pull (ask me how I know....).

Thank you! I am actually more concerned about what happens when it's time to replant tulip bulbs the following fall, though - can you dig through the top layer of crocus corms and shove them in, or do you end up having to remove the entire first layer of dirt/corms and plant new tulips, then replace all the crocuses? I am concerned that that is both a PITA and might interfere with the crocuses' naturalization activities. Perhaps it's better to leave tulip bulbs out of in-ground lasagna for this reason, and layer only bulbs that perennialize/naturalize?

Have your cake and eat it. I grow tulips in pots....and when they go over, immediately the foliage dies down, overturn the pots, sort out the biggest tulip bulbs (they will have started to split into offsets)...and replant in a nursery bed or area where they can remain undisturbed to naturalise. As these areas are in short supply, I use the edges of my veg beds )interplanted with parsley, fennel and caraway). The flowers will be smaller (but will also withstand wind and rain)...and some will be blind until the offsets reach maturity (2-3 years). Just remove any flower heads after flowering and ignore the developing bulbs to reappear and thrive as they wish. An annual topdressing of blood, fish and bone or such will boost vigour.