Gardening in Arizona is unlike gardening anywhere else in the country. Since we are hot and dry, we experience a specific set of challenges, even for experienced gardeners. While much of the United States follows a traditional spring planting schedule, Arizona gardeners have two distinct growing seasons that allow for flowers nearly year-round. By understanding when to plant cool-season and warm-season flowers, you can create a garden that is continuously full of color despite the deserts' challenging climate.

Whether you're growing in raised beds, containers, or an in-ground landscape, success starts with planting the right flowers at the right time. At John's Plant Adventures, we specialize in helping gardeners create beautiful cottage-style flower gardens with seasonal flowers that thrive in warm climates. This guide will help you understand Arizona's unique gardening seasons and set you up for success throughout the year.

Understanding Arizona's Growing Seasons

Most of Arizona's population is in the Phoenix and Tucson metro areas, which fall within USDA Zone 9a, 9b or 10a. Instead of one long growing season, gardeners enjoy two primary planting windows:

• Cool Season: October through March

• Warm Season: April through September

There is some overlap in the seasons where both cool season and warm season flowers may thrive (April + October). With these two main growing seasons, we are able to grow a wide variety of flowers that other climates have difficulty growing. There are a few more additional planting windows within the two big ones, and we’ll chat more about that later in the article. 

Cool-Season Gardening

For many Arizona gardeners, the cool season is the best time of year to be in the garden. As temperatures finally drop below 100°F, spending time outdoors becomes enjoyable again, making it the perfect time to plant for months of beautiful blooms. Unlike colder climates, where gardens go dormant for the winter, Arizona's cool-season flowers continue to grow throughout the winter months and often reach their peak from February through April, depending on the variety. 

Cool-season flowers establish best when planted during the mild days of early fall. In the low desert, we typically begin planting when nighttime temperatures consistently fall into the low 60s and 50s. This gives plants plenty of time to develop strong root systems before winter which results in healthier, fuller plants with longer bloom periods and more abundant flowers in spring.

Many cool-season flowers are exceptional cut flowers, making them perfect for bouquets, cottage gardens, and bringing fresh blooms indoors throughout the season.

When designing a cool-season garden, we like to combine long-blooming border flowers with taller cut flowers. This creates a garden that provides continuous color while adding height, texture, and plenty of flowers to harvest.

Border flowers bloom shortly after planting until they are removed in late spring, creating a reliable carpet of color throughout the season. Cut flowers, on the other hand, add structure, layers, and drama to the garden. Although many have a shorter bloom window, they're well worth including for their striking flowers and beautiful bouquets.

Popular Cool-Season Cut Flowers

• Snapdragons
  
  

• Delphiniums / Larkspur
  

• Sweet Pea

• Ranunculus
  

• Anemones
  

• Foxgloves
  

• Stock

• Poppies
  

• Scabiosa

• Bells of Ireland

• Orlaya

• Craspedia

Popular Cool-Season Border Flowers

• Sweet Alyssum

• Violas/ Pansys

• Calendula

• Dianthus

• Dusty Miller

• Ornamental Kale & Cabbage

• Lobelia

When to Plant

Most cool-season flowers should be started from seed indoors in August or September or transplanted as plugs between October and November, depending on your location and the variety. Planting cut flowers before they bloom allows strong root systems to develop before winter, resulting in larger, healthier plants and spectacular spring blooms.

Why Cool-Season Gardening Is So Special

One of the greatest advantages of gardening in Arizona is that flowers continue growing during the winter while many other parts of the country are covered in snow. We have one long cool season while other states have shorter windows for their cool season crops in spring and fall.  This extended growing period produces exceptionally large plants with long bloom windows, making Arizona one of the best climates for growing premium cool season flowers. 

Covering cool season flowers?

We occasionally get frosty nights between December and early February here in the Phoenix Valley. Because of this, we get asked this question all the time. Should I cover my flowers? And my answer - It depends. 

Most cool season flowers (especially cut flowers, cabbages, and pansys) are extremely winter hardy. They can even take a hard freeze. In fact this may get them to bloom better come spring. Some flowers are more frost sensitive than others. We typically cover things like petunias, alyssum, and geraniums. 

My general advice is - if a frost is coming, cover only flowers that are blooming. Even if a plant is frost hardy, the blooms may get damaged in a freeze event. 

Warm-Season Gardening

As spring temperatures rise into the 90’s, it's time to transition into Arizona's warm-season garden. While summer heat can be intense, many flowers absolutely thrive in the desert when planted at the proper time.

Warm-season flowers are known for their vibrant colors, heat tolerance, and ability to bloom continuously throughout summer and into fall.

Popular Warm-Season Flowers

• Zinnias

• Gomphrena

• Celosia

• Cosmos

• Sunflowers

• Marigolds

• Angelonia

• Vinca

• Salvia

• Pentas

• Scaevola

• Lisianthus

• Lantana

• Sweet potato vines

When to Plant

You can start warm-season flowers indoors in February and March, then transplant them outdoors in April and May. This gives plants time to establish strong root systems before the intense summer heat arrives.

Unlike cool-season flowers, warm-season flowers thrive in warm soil and mild nights. We typically wait to plant until nighttime temperatures are consistently in the 50s or warmer. Although the average last frost in the low desert falls between late February and early March (depending on your location), we usually wait a few more weeks before planting. Even after the danger of frost has passed, nighttime air and soil temperatures are often still too cool for heat-loving plants.

Waiting for warmer conditions helps warm-season flowers establish more quickly, experience less transplant shock, and produce stronger growth heading into summer.

Monsoon Planting

Many Arizona gardeners take advantage of the monsoon season by planting a fresh round of warm-season flowers in July and August. While summer temperatures are still high, the increased humidity, cloud cover, and frequent afternoon rainstorms create better growing conditions than the intense heat of early summer.

Monsoon planting gives fast-growing annuals time to establish before temperatures begin to cool in the fall. With proper care, these flowers will provide color through late summer and continue blooming through fall.

We like to plant flowers that are quick to grow from seed to bloom, typically between 50-75 days. With the warmer growing conditions, plants grow much quicker than spring successions. 

Some of our favorite flowers for monsoon planting include:

• Zinnias

• Celosia

• Cosmos

• Sunflowers

• Marigolds

• Basil

• Amaranth

• Millet

If you're looking to refresh your garden after the toughest part of summer, monsoon season is the perfect opportunity to add a new wave of color before transitioning into Arizona's cool-season garden.

Gardening Through Arizona Summers

Summer gardening in Arizona requires a few adjustments. We want to set our plants up for success when gardening in our extreme climate. 

Water deeply and consistently. We water our plants daily in the ground during the hottest parts of the summer. If growing in containers, we recommend 2x per day watering. The bigger the pot the better during the summer months. Leave the small pots for cool season gardening. Larger pots hold more soil, which means more moisture and root protection your plants have access to. 

• Apply mulch to keep soil cooler and reduce evaporation.

• Grow heat-loving flower varieties.

• Provide afternoon shade for plants that appreciate extra protection.

• Provide shade cloth for exposed areas

• Fertilize annuals regularly to encourage continuous flowering.

With proper care we can enjoy flowers all season long. Some flowers, despite being heat tolerant, need to be succession planted throughout the season. These are flowers like sunflowers, zinnias, celosias, and amaranth. 

Gardening Year-Round in Arizona

One of the greatest benefits of living in Arizona is the opportunity to garden nearly every month of the year. Rather than putting your garden to bed for winter, you'll simply transition between cool-season and warm-season flowers.

By planning ahead and planting with the seasons, you can enjoy:

• Continuous blooms throughout the year.

• Fresh-cut flowers for months on end.

• Healthy, vigorous plants that thrive in Arizona's climate.

• A colorful garden that changes beautifully with the seasons.

Whether you have a large space to garden with, or just a few containers on your balcony, we can all enjoy some beautiful flowers even in Arizona's unforgiving climate. 

At John's Plant Adventures, we're passionate about helping gardeners grow thriving cottage gardens in warm climates. Explore our growing guides, browse our flower seeds and seedlings, and discover new varieties that will keep your Arizona garden blooming season after season.