Tom Carwin, on gardening | Dahlia cultivation blooms in spring – Santa Cruz Sentinel

Tom Carwin, on gardening |  Dahlia cultivation blooms in spring – Santa Cruz Sentinel

Dahlia flowers. (Monterey Bay Dahlia Association/Contributor)

As we emerge from the depths of the pandemic and seasonal rainstorms and into the spring season, we are free to find renewed optimism and creative urges for gardening.

There are many ways to respond to these desires, so it pays to focus.

A really good option this time of year is to develop your landscape by adding dahlias, which are very attractive as garden plants and grow well in the Monterey Bay area. This is the perfect time of year to plant dahlias, so let’s dive into this genus.

The genus Dahlia falls within the Asteraceae or Compositae family of plants, which also includes sunflowers, chrysanthemums, chrysanthemums and zinnias. The dahlia is native to Mexico, which has declared it its national flower.

The genus includes 42 species. The familiar garden dahlia (pinnata species) includes more than 50,000 cultivated varieties, and is said to be the result of the hybridization of two species: D. coccinea and D. coccinea. sorensenii.

Dahlia flower. (Monterey Bay Dahlia Association/Contributor)

Hybridizers have created a large and ever-increasing number of cultivated varieties with many unique characteristics. Intensive hybridization and genetic modification have increased “dahlia flowering, radial flower shapes, color diversity, size of individuals, and flowering time.” The accompanying photographs, provided by the Monterey Bay Dahlia Society, provide a glimpse into the extraordinary diversity of this genus.

Garden dahlias are bushy perennials that grow from tuberous rhizomes to heights ranging from 12 inches to 6 feet, depending on the variety. It blooms in spring, reaching its peak in late August.

Dahlias generally need the support of a stake to maintain their height. The usual practice, when mounting a tuber, is to insert a bamboo or similar stake nearby, carefully not piercing the tuber.

A less obvious method is to install a 1-inch diameter plastic pipe next to the tuber, with the top of the pipe visible just above ground level. Later, when you need to support the plant, insert a thin bamboo stake into the pipe and tie the plant stem to the stake.

Larger dahlias, 2 to 6 feet tall, are attractive in the landscape. They can be grouped in drifts or installed in small groups throughout the garden. Many gardeners will include a personal selection of bloom colors and shapes, while some may choose a mass effect of a preferred color or shape. There are many options.

Smaller dahlias, 1 to 2 feet tall, can be displayed as border plants or grown in containers.

All dahlias do very well as cut flowers. Some varieties have been bred to produce many flowers, while others are destined to produce smaller numbers of high-quality flowers for competitive displays. Your choices should reflect your goals.

Dahlia stems turn brown in the winter, usually by mid-November in the Monterey Bay area. In cold climates, hard frosts kill dahlias, but in the temperate climate of the Monterey Bay area, gardeners can cut the old stems to the ground and leave the tubers in the ground to grow again in the spring.

Another option is to dig up the tubers to transplant or propagate plants in the garden, or share the tubers with other gardeners. For information about farming, see ‘Advancing your knowledge’ (below).

Mark your garden calendar

The Monterey Bay Dahlia Association will hold its annual tuber sale from 9 to 11 a.m. April 15 in front of the Red Apple Cafe in the Deer Park Shopping Center, 783 Rio Del Mar Blvd., Aptos. This event will be held outdoors rain or shine.

This exceptional annual event is an excellent opportunity to obtain affordable tubers of locally grown dahlias, grown by community members, some of whom are commercial growers, distinguished hybridizers, and leaders of local and national communities of home gardeners who appreciate dahlias.

“Countless dahlia farms advertise their tuber sales or open them first to newsletter subscribers, then to their followers, and finally on their websites,” said Julie Eupemi, president of the Monterey Bay Dahlia Society. “However, they consistently sell out of certain items within seconds, with all of their stock selling out within minutes of going live.” The tubers in your shopping cart don’t belong to you yet, and are often gone when you rush to check them out.

However, when you shop in person, the tubers you put in your basket are yours to buy.

“The tubers are organized by size and contain pictures of what the flower will look like once the tuber grows,” Eufemi said. “We also have members available to talk about dahlias and answer questions.”

Dahlia gardeners browse the sale offered by the Monterey Bay Dahlia Society. (Contributed)

The community will receive shoppers in small groups to ensure an uncrowded shopping experience. However, it’s a good idea to arrive early to choose from the wider selection. This event is a fun way to add great color to your garden.

Advance your knowledge

To learn about dahlias, visit and scroll down the Grow and Know listings. As you explore the wealth of information on this website, look in particular at the ‘ADS Dahlia Classification and Figures Guide’, which can be found under ‘Knowledge/Classification’.

For a basic review of recommended practices for growing dahlias in your local climate, visit the Monterey Bay Dahlia Society’s website at, go to the Resources menu and click on “How to Grow Dahlias.” This site also contains information about joining the community, a social resource for ongoing learning about growing dahlias and sharing plants.

For a lively online video demonstration of growing dahlias, browse, search for “Dahlia Growing 101” and scroll down a bit to “Dahlia Growing 101: How to Grow Great Dahlias!” A knowledgeable presenter provides a tutorial on growing these plants. The video lasts 32 minutes and covers all aspects of farming. The speaker speaks quickly, so you can take notes or replay the video to absorb everything she has to offer. Tip: Scroll below the video and click Show More to get links to a list of topics.

Reminder: The Garden Conservatory will present a webinar titled “Piet Oudolf at Work” at 11 a.m. on April 13. This virtual event will be a conversation between two long-time collaborators of renowned Dutch garden designer Piet Oudolf: Laura Ekasetya of Lurie Garden and Meredith Simpson will discuss Oudolf’s methods, inspirations and projects. His work will be featured in a soon-to-be-published major monograph entitled Piet Oudolf at Work. The book offers a new insight into Oudolf’s work and creative practice, both from a horticultural and artistic perspective, and showcases high-profile and lesser-known gardens.

Registration for the webinar costs $5 for Garden Conservancy members and $15 for general admission. The fee for both the webinar and a copy of “Piet Ourdolf at Work” is $70. For information and to register, visit

Tom Carwin is a past president of the Friends of the UC Santa Cruz Arboretum and the Monterey Bay Iris Society, a past president and life member of the Cactus and Succulents Society of the Monterey Bay Area, and a UC Santa Cruz Life Master Gardener (certified 1999-2009). He is now a board member of the Santa Cruz Lodge Association, and active with the Pacific Horticultural Society. To see daily photos from his garden For information about garden training and an archive of On Gardening columns, visit Email your comments or questions to

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