When the Dutch got their hands on tulips through the Ottoman Empire in the seventeenth century, they started to breed them to suit their own climate and conditions. The Netherlands is cool, damp and cloudy. The lowland soil is sandy rather than clay like on the Asian steppes.
Centuries of Dutch breeding rendered most tulip hybrids unsuitable for growing successfully in a steppe climate. That's why many tulips planted in Colorado fail to persist beyond their first season. The one exception is the group called "Darwin hybrids." These retain the vigor of their wild ancestors. (Their are other hybrids and nearly-wild tulips that thrive here as well, but these are smaller and shorter. I'm focused here on the tall classic tulips that most people picture when they think of tulips.)
There are about 20 Darwin hybrids varieties available in a wide range of colors, from red, pink and purple to yellow, orange and white. They bloom in May and grow about a foot tall. In my experience, these Darwins return year after year and often multiply. Many of mine were planted 20 years ago and are still going strong.
In clay soil, plant them five or six inches deep with the pointed end up. In a sandy soil, consider planting them a few inches deeper. There's no need to modify your soil. When you plant, enhance your future spring display by adding pansies on top. You had to dig the holes anyway, so it's very little extra work to plant the pansies. Tulips also look pleasing coming up through perennial groundcovers that bloom in spring such as creeping phlox or lamium.
Tulips need very little care. It's actually good to neglect them in spring. Don't cut off the foliage after the blossoms fade; let it wither and die naturally. If you cut it off, you are depriving the bulbs of their opportunity to renew themselves for the next spring. Leaves are solar collectors. (This applies to all other bulbs as well such as hyacinths and daffodils.)
The main enemies of tulips (besides overly-tidy gardeners) are rodents. Although squirrels and mice sometimes go after freshly-planted bulbs, voles and ground squirrels are a more serious threat. If rodents constantly plague your garden, skip tulips and plant daffodils instead, which are poisonous.
Tulips may be planted at any time in fall as long as the ground has not yet frozen. That window of opportunity closes around Thanksgiving. By selecting the right kind of tulips--and planting them with suitable companions such as pansies or creeping phlox--you'll have a beautiful display this spring. By leaving their foliage intact until it withers, you'll have a beautiful display for decades to come.
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