The species tulips I have have all come true in spite of the fact I have many other tulips in my garden. Example my Tulipa tarda started with 5 bulbs and I have at least 40 -50 blooming sized bulbs now. The flowers are all yellow and white even though I have another species (magenta, can't remember the name at the moment) no more than 15 feet away, neither one has shown any changes in colour amongst the offspring. It does take a couple years though for the seedlings to get to blooming size. It also depends on looks, if your tulips are in a garden where you don't want tulip foliage well into the summer than I wouldn't leave them as they can look rather ratty come July. The tulip species also propagate from offsets for example
In each one of these pictures the clumps of tulips all started from one original bulb. Please excuse the dandelions in the first photo, they are in my cactus bed and are VERY hard to weed.
