• Marcia Tatroe

Winter Annuals

By Marcia Tatroe:

California poppies -- sometimes too easy to grow, short lived perennials also come in different hues, which won't overwhelm your garden. Photos; Tatroe Images
California poppies -- sometimes too easy to grow, short lived perennials also come in different hues, which won't overwhelm your garden. Photos; Tatroe Images

How many Front Range gardeners can say they celebrate March 21st, the official first day of spring, with a garden full of flowers? Swaths of bulbs can do the trick but it’s a bit late to be thinking about planting early flowering crocus—they needed to go into the ground months ago. Other than vowing to plant bulbs this coming September for next year, what you can do is to turn to another group of relatively unknown flowers that, started now, promise to be in bloom by the end of March and into April well before robins are even considering a move back north.


March and April is the high season for winter annuals, wildflowers from dry summer environs that have evolved to rely on whatever moisture they receive in late fall and winter. Winter annuals complete their life cycle when pollinators first brave the lengthening days of approaching spring but before real heat sets in for the year. Plant these on Mother’s Day and they’ll expire from heat before they have a chance to bloom.


Death Valley is a good example. When my husband, Randy and I learned that a good bloom was happening in January 2016 we made airline reservations and headed out to witness this phenomenon for ourselves. It was still snowing as we drove from Las Vegas to the park with nary a blossom in sight. All that changed when we hit the east entrance and a floral spectacle unfolded. Fields of flower

At Denver Botanic Gardens, Mike Kintgen has been sowing winter annuals in areas of open gravel: (above) yellow Coreopsis stillmanii with lavender birds eye Gilia tricolor and five spot Nemophila maculata
At Denver Botanic Gardens, Mike Kintgen has been sowing winter annuals in areas of open gravel: (above) yellow Coreopsis stillmanii with lavender birds eye Gilia tricolor and five spot Nemophila maculata

s—winter annuals all—carpeted the valley canyons and floor for 100 miles. All this jump-started by one wet spell the previous autumn. A second good rain while we were visiting assured the flower show would continue until summer’s heat arrived.


When we visited California again in mid-April 2016 this time the Sierra foothills north and east of Sacramento were carpeted with wildflowers thanks to the same Pacific storms from the previous autumn that brought flowers to the driest deserts. Here entire fields were painted blue, gold, white and purple, winter annuals interspersed with native bulbs of every description.


It turns out that the drier the environment, the greater the proportion of annual flowers, a good strategy where the norm is months or years with little moisture. In years with precipitation the seed germinates, flowers and sets seed very quickly ensuring the species survival as seed, overkill in our climate. Although not many winter annuals are native to Colorado fortunately harsher habitats in the western US like the cold deserts of the Southwest, the Sierra foothills and oddball places like Table Mountain in southern Oregon offer an abundance of choices—our one limitation is cold hardiness of the seeds and seedlings. To be safe choose varieties labeled “cold hardy.” The only other requirement for winter annuals is for open soil and plenty of sunlight.

Collinsia heterophylla
Collinsia heterophylla

Undoubtedly, the easiest to grow is the indestructible California poppy Eschscholzia californica. There are many species and cultivars beyond the ubiquitous bright gold state flower, a short-lived perennial that generally acts more like a reseeding annual. For 25 years I’ve had a love/hate relationship with this sometimes too successful wildflower. Some seasons I declare war on the invading throng and remove hundreds of seedlings. Other years I wait until the flower color is evident and pull only the gold, leaving less vigorous white, cream and pink. After a bad winter, and feeling grateful for any sign of life at all, I let them all stay and compromise by cutting all to the ground after the first flush of flowering slows. California poppy will rebloom in late summer when temperatures cool.


If you fear being overrun by California poppies, plant only the differently hued, ruffled or double forms. These can be difficult enough to break the heart of the pickiest gardener. Or try the diminutive desert gold poppy Eschscholzia glyptosperma that likes sandy soil, pale yellow pastel poppy E. caespitosa or the true annual E. californica ssp. mexicana.


Of other native winter annuals I’ve also had good luck with pinkish-white mountain phlox Linanthus grandiflorus, Texas bluebonnet Lupinus texensis, purplish-red Mimulus bigelovii, California bluebells Phacelia campanularia and tansy scorpion flower P. tanacetifolia. Sadly, none of these reseeded for me.


To see a display of winter annuals growing in a public garden, visit Denver Botanic Gardens in late March and April where you’ll find winter annuals growing in the Rock Alpine Garden and on Dryland Mesa. Senior Horticulturalist Mike Kintgen has been sowing these in areas of open gravel for several years. He recommends getting the seed out very early because most require at least six weeks of cold to germinate. You’ll find tiny yellow daisies of Coreopsis stillmanii, delicate lavender birds eye gilia Gilia tricolor, five spot Nemophila maculata, pagoda-like Chinese houses Collinsia spp., brilliant blue desert bluebells Phacelia campanularia, and soft yellow tidy tips Layia platyglossa.


Panayoti Kelaidis, Director of Outreach at DBG, broadcasts seed over snow sometime between November and January after a hard frost, first mixing a couple of handfuls of sand with the seed to help distribute them evenly over large areas. Fine soil or potting mix would also work. I’ve always waited until a wet, sloppy snow is forecast.

In any case keep the seedbed slightly moist until seedlings appear. Whenever arctic weather is heading your way after the plants are well up, throw a frost blanket over the bed to protect seedlings from sub-zero cold in case snow doesn’t fall. If all else fails try again sowing seeds in large containers where they are easier to look after.


Try a few winter annuals and let them dispel the myth that Front Range gardeners can have flowers are only for the short growing season between Mother’s Day and the end of summer.


For seed sources, go to:

Annie’s Annuals, www.anniesannuals.com

Applewood Seed Co., www.applewoodseed.com

bbbseed, www.bbbseed.com

Plants of the Southwest, www.plantsofthesouthwest.com

Theodore Payne Foundation, theodorepayne.org

Marcia Tatroe is a garden designer, author and educator who lives in Centennial.