When to Start Seeds in Zone 9

If you live in zone 9, you have the benefit of being able to grow vegetables and flowers throughout much of the year. Mild winters allow hardy plants to stick around, and early springs mean you can tuck tender seedlings in the garden while much of the country stares out at frozen ground and frost-cloaked perennials.

However, the hot, long summers stress many plants and prompt earlier planting dates. All these factors may have you wondering just when you should start seeds.

I’ll explain the growing conditions present in zone 9 and introduce you to factors you should consider when determining your planting dates. Then, I’ll provide a basic overview of when to start common seeds so you can get your garden off to a great start.

Where is Zone 9?

The recent updates to the USDA Plant Hardiness Zone Map have slightly changed the regions that are designated as zone 9. However, this zone is still reserved for warm areas in southern or western coastal parts of the country.

Some areas in this zone include central and northern Florida, southern Texas, a swath of coastal Oregon, the shoreline of the Gulf of Mexico, and much of northern California, including large cities such as Fresno, Bakersfield, Santa Rosa, and Sacramento. Other notable cities in this zone include Austin, Houston, Dallas, San Antonio, New Orleans, Baton Rouge, Gainesville, and Tallahassee.

Climate Considerations

It’s important to remember that the lowest temperature determines an area’s hardiness zone. So, while all areas in zone 9 experience a wintertime average low temperature between 20-30°F, they may experience different weather throughout the rest of the year.

In general, this zone experiences early last frost dates in the western half of the US. For example, the average last frost date is March 9 in Houston and February 17 in Sacramento. That means you can begin planting frost-sensitive plants outside by early spring or even late winter.

However, you must check your region’s final frost date to be 100% sure of your local final frost dates. While zone 9 typically gets warmer quicker than cooler zones, many southeastern states may experience cold storms with a risk of frost later in the season. Your zone indicates your average annual coldest temperature but does not predict your final frost date!

Temperatures above 80°F often start to appear between late March and early May, and summers are long and hot. The humidity and rainfall vary by location—look up past weather data for your area to give you an idea of what to expect.

How to Determine When to Start Seeds

While determining when to start seeds may seem like it involves a bit of plant-related sorcery and guesswork, you can actually rely on past data to figure out when to plant your seeds. Two of the most important factors to consider are your average last spring frost date and your average first fall frost date.

You should transplant frost-sensitive crops like tomatoes, basil, zinnias, and marigolds outdoors after the last frost arrives. However, if you want to plant seedlings in your garden ASAP, plan to start seeds indoors when it’s still chilly outside.

Hot summers are your main threat when it comes to heat-sensitive crops like kale, cabbage, radishes, and violas. Starting seeds in the winter or early spring will allow these plants to mature before scorching days arrive. Planting another round of seeds in the early fall allows you to harvest these cold-tolerant crops in the late fall and winter.

Transplanting vs. Direct Sowing

I like to break down my seed starting into two groups: transplanting and direct sowing. Since I plant the seeds of direct-sown crops straight into the garden, there isn’t much planning required. You just need to pick the right date and ensure you have available garden space.

Transplanted crops require a bit more work. First, I determine when I intend to plant the seedlings in my garden. With this date in hand, I figure out how long it will take for plants to grow from seeds to mature seedlings and count backward to determine the seeding date. 

If you’re not sure how long it takes a plant to go from seed to mature seedling, look at the seed packet for help. For example, the ‘Copenhagen Market’ cabbage packet instructs you to start seeds four to six weeks before your ideal transplant date.

When to Start Seeds in Zone 9

Thanks to zone 9’s mild weather, you can garden outdoors year-round with the right crops. The best times to start cool-weather crops are mid-winter and late summer, while late winter or early spring is the best time to start plants that prefer warmer weather.

When to Start Vegetable and Flower Seeds Indoors in the Spring

You’ll need to wait until your last frost passes before transplanting frost-sensitive crops like tomatoes and zinnias outdoors. However, starting seeds indoors when the danger of frost exists allows you to get seedlings in the ground once the weather warms.

Growing multiple successions of summer crops like tomatoes, cucumbers, and zinnias will allow you to harvest crops throughout the summer continually. I find that even if the first planting succumbs to a fungal disease like downy mildew, the later planting will continue to produce.

The chart below shows an estimated range across all zone 9 regions nationwide. Be sure to check your average annual last frost date against the planting timing on your seed packet to determine the exact timing for your area.

When to Direct Seed Flower and Vegetable Seeds Outdoors in the Spring

Since the soil warms up early, you can successfully directly sow many seeds in the new year. Late winter and early spring are the best times to plant cool-weather crops like greens and roots, while mid-spring to early summer spring are the best times to direct sow beans, squash, and other warm-weather crops.

Since you can plant frost-tolerant seedlings outdoors earlier, you can also start these seeds outdoors earlier in the year. Planting cool-weather crops outdoors earlier in the year will allow the plants to grow before hotter days arrive. However, if the weather is still too cold, you may see delayed germination as the soil temperatures may not be warm enough for good germination. Similarly, you may see slow growth initially if the weather’s still a little chilly for the plant.

Since you can succession plant multiple rounds of seeds in the spring, I’ve included a range of planting dates. You can plant your first round of seeds at the range’s start and the second round a few weeks later. Alternatively, plant one round of seeds anytime during the suggested range.

When to Start Seeds for Fall Planting

By the fall, it’s easy to be tired from summer gardening chores. But rather than throwing in the towel on your garden, use this time to plan your fall plantings. Due to long summers, you can plant cool-weather crops later in the late summer or early fall for a fall or winter harvest.

When starting seeds in the summer, remember that high temperatures can inhibit the germination of some seeds. You can always start your seeds in a cool garage or air-conditioned home to encourage better germination if you’re in the 90s outside.

With this list, there’s a slight variance to be aware of: check your first frost date to ensure your cool-weather crops will be well past germination and into development as the chilliest weather rolls around. While most of these plants can tolerate a light frost, they need to be at least somewhat developed by that point, and small, newly-germinated plants are more at risk from a frost.

Final Thoughts

You can enjoy a thriving garden year-round by starting the seeds at the right time. Remember to pay attention to your weather and plant seedlings outdoors after the danger of frost and extreme heat has passed.