When To Plant Dahlias In California?

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Don’t know when to plant dahlias in California? Don’t worry; this article will tell you what you need to know. 

First, you must utilize a few windows when they open, or else you risk your dahlias going head-to-head with the BITTER COLD winter in Cali.

Although you might have guessed it, dahlias are primarily planted in the spring after the last frost passes over. 

But what if you live in the milder coastal area of California?

Well, you can plant your dahlias earlier. And in inland or higher elevation areas, it takes a bit longer. 

We will discuss all of this but in their respective zones. 

When To Plant Dahlias In California

The question you should be asking is: What is the climate condition of my region?

The USDA Hardiness Zones or Plant Hardiness Zones per sa. But here is a rule of thumb for planting dahlias in various parts of Cali: 

Coastal Areas (Zones 9-10): These regions experience mild climates. That means you can start sowing your dahlias as early as February or March.

Central Valley And Inland Areas (Zones 8-9): You must be patient until mid or late March for the late frosts to pass. 

Mountain And High Elevation Areas (Zones 7-8): Higher elevation regions always have a later last frost date, so wait until April or May before planting.

How Long Do Dahlia Tubers Last?

Sorry, I can’t give you an accurate duration, but stored dahlia tubers can last several months. 

Now, how long they last depends solely on how they are stored. But if done correctly, you can successfully replant your dahlia tubers in subsequent growing seasons.

However, the winter season is when most Dahlia tubers turn bad. If you want to learn How To Store Dahlia Tubers Over Winter (Step-by-Step), you ONLY have to do five things.

 I recommend that link, as I will take you through each step by hand. 

How Long Do Dahlias Bloom?

It takes about 60 to 120 days for newly planted dahlias (from tubers) to bloom.  

However, factors like the dahlia variety, planting time, growing conditions, local climate, and care provided can slightly bend the rules. 

For instance, more petite or shorter variants tend to bloom earlier regardless. Meanwhile, the more complex varieties take longer to sprout and produce blooms. 

Spring season favors Dahlias more, especially after the last frost has passed. This is why most gardeners plant during this window. 

Again, it depends solely on your location and planting time. Some gardeners enjoy their blooms from early summer until late summer. 

Some varieties may reward you with blooms that last until the fall season and end when the first frost hits the ground.

To enjoy such an extensive bloom period, a lot has to be done with providing the proper care —including adequate watering, fertilizing, regular deadheading (removing spent flowers), and protection from pests and diseases. 

But a surefire way to secure a continuous display of color blooms is by planting a mix of early, mid-season, and late-blooming varieties in your garden. 

Can Dahlias Survive Heat?

Dahlias are not only sensitive to cold; they are also vulnerable to heat. 

While they can survive in heat, they have their limits. 

Prolonged exposure to extreme heat, about 90 degrees Fahrenheit, will stop dahlias from growing. And indeed, it will not flower. 

High temperatures can lead to water stress and dehydration, cause protein denaturation, oxygen deprivation, and nutrient imbalance, and can damage the photosynthetic machinery.

This puts an enormous pressure on the plant, limiting their chances of survival. 

How Do You Protect Dahlias From Heat?

One of the most popular methods is mulching. 

Mulch does one thing well: it helps to retain soil moisture and stabilize the soil temperature. 

So, since Dahlias have shallow feeder roots laying just underneath the surface, covering the  

soil with about 2 to 3 inches of mulch will help insulate and shield the roots against extreme heat. 

Thicker mulch could also be a problem as it may prevent water from sinking into the soil. So take note. 

Regularly watering your dahlias helps reduce excessive evaporation and prevent sunburn. 

Giving them a nice bath or pooling them a little when the temperature is up is not a big deal. They won’t drown. In fact, they will thank you.

Most gardeners consider the drip irrigation system an effective watering method since it reduces the risk of fungal diseases and conserves water. 

Other things worth considering are: 

  • Shade Provisioning: Temporary shade (cloth or lightweight fabric) can be a shelter during the blistering heat. 
  • Avoid Fertilizing Excessively: The scorching sun will react with the amount of fertilizer in the soil, which can stress the plants. If you must use fertilizers, it should be a balanced, slow-release fertilizer used moderately.
  • Pruning Also Helps With  Air Circulation And Avoid Overcrowding: Dahlias need room for air, which could be through pruning the lower leaves. However, if you overcrowd the dahlias with neighboring plants, it could limit good air circulation and put the plants in fierce competition for resources. 

Finally, a lot of people stick to the California Last and First Frost Dates. I’m not sure how that helps, but here is what it looks like: 

CityLast Frost DateFirst Frost Date
Los Angeles Infrequent Infrequent
San Jose January 28th December 8th 
San Diego Infrequent Infrequent 
San FranciscoInfrequent Infrequent 
FresnoFebruary 13th December 1st 

I won’t advise you to bank on these frost dates since mother nature has some cruel tricks up her sleeve. 

As we have seen case after case, some years, the last frost came MUCH later. Whereas, there are years when it comes MUCH earlier. 

However, a surefire way is checking your local weather forecast. And you should be diligent about it. That is the only time you can fully utilize those windows. 

Should the frost catch you off guard, be quick to bring them inside if potted. 

However, if they are sowed in the ground, you MUST cover them in burlap and pray they survive. 

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