For the excitement of spring, now is the time to relax

excitement of spring
(Courtesy of Tom Karwin)

We've written about the Bay Area's most famous plant groups: California natives, dahlias, lilies, roses, and succulents. In today's column, we focus on tulips, which are popular in many parts of the country but rarely seen in our gardens.

Tulips are members of the genus Tulipa, which is one of 15 genera in the lily family (Liliaceae). The genus includes some 75 species that are native within a wide area from southern Europe to the Middle East and Central Asia.

Tulips are widely cultivated and are available in a wide variety of colors, shapes, and bloom times. There are 15 divisions of tulips based on flower morphology and plant size. These divisions are also listed within three categories based on their blooming season: early, mid, and late.

Despite the impressive diversity of tulip crops today, local gardeners generally do not grow these plants because much of the Bay Area lacks the cooling period that most tulips require during their dormancy.

Most tulip bulbs available at mail-order nurseries or local garden centers are recommended for planting in USDA Zone 8 or below. Monterey Bay, for example, is in Zone 9, which has cool and even freezing temperatures but doesn't provide the 12 to 14 weeks of cold soil (temperatures below 55 degrees) that tulips require to bloom during the following spring.

It is possible to get lucky with a variety of tulip that is adapted to the local climate. I had regular flowers of Tulipa 'Peer Gynt', purchased in 1998 during a visit to Keukenhof Gardens in the Netherlands. It has bloomed every year since, without any special care on my part. Obviously, not all tulips require the same cold treatment.

But not all is lost! You can grow tulips in a temperate climate using a proper strategy. Here are approaches to consider:

Pre-chilled tulip bulbs

Some online nurseries and possibly local garden centers offer tulip bulbs that have been pre-chilled and delivered in time for planting. For example, go to and search for "pre-cooled". As the season progresses, more temperate gardeners and cold-weather procrastinators will want to grow tulips, and more nurseries will offer pre-chilled bulbs.

DIY bulb-chilling

You can order tulip bulbs early enough that you cool them below 55 degrees before planting in late November or mid-December. Some online recommendations call for a chill period of as little as four weeks, but the optimal length is 12 weeks, reflecting the natural period of tulips. Bulbs should be refrigerated in a paper bag and away from fruits or vegetables, which give off ethylene gas that can kill the tiny flower inside the bulb.

This approach requires that you order your bulbs early. Most mail-order nurseries are set up to ship tulip bulbs on a schedule appropriate for areas with the necessary natural cooling period, so you should place orders by phone in advance to confirm you need the bulbs in time for an artificial cooling period.

Tulips must be planted in November in most parts of the country. This schedule allows the bulbs to come out of summer dormancy and develop roots before the ground freezes and then flower when warm weather arrives in late March or early April.

It is acceptable to plant the bulbs in late fall in the Bay Area, anticipating that the ground is unlikely to freeze over the winter and will not be warm enough to encourage premature budding.

Whether you plant prechilled bulbs or cool them yourself, plan to lift the bulbs after the foliage has matured (usually around mid-May), store them in a cool, dry place over the summer, and provide a cooling period again before replanting them. late fall.

Buy tulips from temperate zone species. As noted above, there are many species of tulips, some of which are native to climates similar to the temperate Bay Area. These species are attractive in their own right, though perhaps not as showy as the more recent crop of cultivars.

Species to search online include Tulipa clusiana (several named varieties can be found), T. saxatilis, and T. urumiensis. These species are on the Zone 9 list and could be planted in the fall, but providing the usual chill period could provide optimal blooms.

Advance your gardening knowledge

Preparing for today's column led me to several tulip-related websites of particular interest. For more information on the Tulipa genus, check out these sites.

For brief descriptions of the 15 divisions of the genus Tulipa, see Find tulips and scroll down to "Horticultural Classification".

For an overview of tulip cultivation, visit

For a discussion of tulips’ chilling needs, visit and search for “cold period.”

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