Start These Flower Seeds In May For Colorful California Summer Gardens
May in California is basically the sweet spot that flower gardeners dream about. The soil has finally warmed up, the last of the unpredictable spring weather is wrapping up, and the long, sunny days ahead are basically an open invitation to get some seriously beautiful things growing.
If you’ve been waiting for the right moment to start flower seeds, this is it and the timing could not be better.
The flowers you start this month are the ones that are going to be putting on a full show right when summer hits peak California energy.
Think saturated colors, pollinators going absolutely wild, and garden beds that stop people in their tracks. The best part is that starting from seed is cheaper, more satisfying, and gives you way more variety than anything you’ll find at a nursery.
Grab your seed packets and clear some space because your best summer garden yet starts right now.
1. Zinnias
Few flowers put on a show quite like zinnias do. These bold, cheerful blooms come in almost every color you can imagine, from deep red to soft lavender, and they absolutely love the warm California sun.
Plant your seeds directly in the garden in May, and you will start seeing blooms in about six to eight weeks.
Zinnias grow fast and are very easy to care for, making them a great choice for beginners. They do best in full sun, so pick a sunny spot with well-draining soil.
Water them at the base of the plant to keep the leaves dry and healthy.
One fun fact about zinnias is that the more you cut them, the more they bloom. So keep a vase handy because your California garden will be producing fresh flowers all summer long.
They also attract butterflies, which makes your garden feel even more alive and colorful throughout the season.
2. Cosmos
There is something almost magical about the way cosmos flowers move in the breeze. Their feathery leaves and daisy-like blooms give any garden a light, airy feel that looks effortless and beautiful.
May is the ideal time to direct sow cosmos seeds in California because they love warm soil and full sunlight.
Cosmos are incredibly low-maintenance. Once they sprout, they practically take care of themselves.
They actually prefer poor soil over rich soil, so you do not need to fertilize them much at all. Overwatering can cause them to flop over, so water only when the top inch of soil feels dry.
These flowers grow quickly and can reach three to four feet tall by midsummer. They bloom in shades of pink, white, red, and deep magenta.
Cosmos are also wonderful for attracting bees and butterflies to your California garden. Plant them along a fence or at the back of a flower bed for a stunning natural backdrop that blooms well into fall.
3. Sunflowers
Nothing says summer quite like a tall, golden sunflower reaching toward the sky. These iconic flowers are incredibly rewarding to grow from seed, and May is the perfect time to get them started in California.
The warm soil temperatures help seeds sprout quickly, usually within seven to ten days.
Sunflowers need full sun, which California has plenty of. Choose a spot that gets at least six to eight hours of direct sunlight each day.
Plant seeds about an inch deep and give each plant plenty of space to grow. Larger varieties can reach six feet or more, while smaller ones work great in containers or tight spaces.
Did you know sunflowers actually track the sun across the sky when they are young? It is a process called heliotropism, and it helps them grow faster.
Once they mature, they face east permanently. Beyond their good looks, sunflowers produce seeds that birds absolutely love.
Growing sunflowers in your California garden means you get beautiful blooms and a built-in bird feeder all in one cheerful package.
4. Marigolds
Marigolds are the workhorses of the summer garden, and California gardeners have counted on them for generations. These tough, vibrant flowers bloom in shades of orange, yellow, and gold, and they keep going all season long without much fuss.
Planting seeds in May gives them time to establish before summer heat really kicks in.
Beyond their good looks, marigolds earn extra points for being practical. Their strong scent naturally repels common garden pests like aphids and whiteflies.
Many California gardeners plant them around vegetables like tomatoes and peppers to help protect those crops naturally without using chemicals.
Marigolds thrive in full sun and do not need much water once they are established. Deadhead the spent blooms regularly to encourage the plant to keep producing fresh flowers.
They also make lovely cut flowers for the home. French marigolds stay compact and bushy, while African marigolds grow taller and produce larger blooms.
Either way, you cannot go wrong adding marigolds to your California summer garden this May.
5. Nasturtiums
Nasturtiums are one of those flowers that surprise people every time. They grow fast, look gorgeous, and you can actually eat them.
The flowers and leaves have a peppery flavor that adds a fun kick to salads and garnishes. May is a great time to sow nasturtium seeds directly in the ground across California.
These flowers prefer poor to average soil and do not need fertilizer. In fact, too much nitrogen will give you lots of leaves and very few blooms.
They love full sun but can handle a little afternoon shade in hotter inland California areas like Fresno or Riverside. Water them moderately and let the soil dry out a bit between waterings.
Nasturtiums come in trailing and compact varieties. The trailing types look stunning spilling over garden walls, hanging baskets, or raised beds.
Compact types are great for borders and containers. Colors range from creamy yellow to deep red and fiery orange.
They also attract hummingbirds and beneficial insects to your garden. Nasturtiums are one of the most cheerful and versatile flowers you can grow in a California summer garden.
6. Mexican Sunflowers
If you want something with a little more drama than a regular sunflower, Mexican sunflowers are your answer. Known botanically as Tithonia, these plants produce vivid orange blooms that look like something out of a tropical paradise.
They love heat, which makes them absolutely perfect for California summers.
Start seeds indoors in early May or direct sow them outside once the soil is warm. Mexican sunflowers grow big, sometimes reaching five or six feet tall, so give them plenty of space.
They thrive in full sun and tolerate dry conditions once established, making them a smart choice for water-conscious California gardeners.
Butterflies and hummingbirds are drawn to these flowers like magnets. The blooms appear from midsummer all the way through fall, giving your garden long-lasting color.
The cut flowers also last well in a vase, so you can bring that orange glow indoors too. Plant them at the back of a flower bed where their height becomes an asset.
Mexican sunflowers are truly one of summer’s most impressive and underrated garden performers in California.
7. Celosia
Celosia is one of those flowers that makes people stop and stare. Its blooms come in two main styles: feathery plumes that look like flames and velvety crested heads that look almost like brain coral.
Either way, the colors are electric, ranging from deep crimson to hot pink to golden yellow.
May is the right time to start celosia seeds in California because this flower absolutely needs warmth to thrive. Cold soil will stall its growth, but warm May temperatures give it the boost it needs.
Plant in full sun with well-draining soil, and water consistently without letting the roots sit in wet conditions.
Celosia is also incredibly heat-tolerant, which makes it a standout performer during those intense California summer stretches. It holds its color even on the hottest days when other flowers start to fade.
Deadhead spent blooms to encourage new ones, or let the blooms dry on the plant for a striking natural display. Celosia also dries beautifully for indoor arrangements, so you can enjoy the color long after summer ends.
It is truly a flower worth growing.
8. Amaranth
Amaranth has been grown for thousands of years, and once you see it in a garden, you understand why. The plants produce long, dramatic plumes of tiny flowers in shades of deep red, burgundy, gold, and green.
Some varieties droop gracefully while others stand tall and upright, creating a bold vertical statement in the garden.
Sow amaranth seeds directly in the ground in May when California soil has warmed up nicely. These plants love heat and full sun, and they are surprisingly drought-tolerant once established.
That makes them a great fit for California gardeners who want stunning color without heavy watering demands.
Amaranth grows fast and can reach three to eight feet tall depending on the variety. The flowers attract birds, especially finches, who love to snack on the seeds in late summer.
Some amaranth varieties are also edible, with leaves that can be cooked like spinach and seeds that are packed with nutrition. Growing amaranth in your California garden means you get bold visual impact, wildlife benefits, and a plant that can practically feed you too.
It is a genuinely impressive summer flower.
9. Four O’Clocks
Four o’clocks earn their quirky name honestly. These flowers stay closed during the day and open up in the late afternoon, usually around four in the evening.
That makes them a fun and unexpected addition to any California garden, especially if you enjoy spending evenings outdoors on a patio or deck.
Plant seeds directly in the garden in May after the soil has warmed. Four o’clocks grow into bushy plants about two to three feet tall and wide.
They bloom in a wild mix of colors, sometimes even showing multiple colors on a single flower. Shades of pink, yellow, white, magenta, and red are all common, and the plants bloom nonstop until fall.
One of their best qualities is their fragrance. Four o’clocks release a sweet, pleasant scent in the evening that drifts through warm California nights.
They attract sphinx moths and hummingbirds, which adds even more life to your garden after sundown. These plants are also quite tough and can handle heat well.
Once established, they form a tuberous root that can be saved and replanted the following year, making them a long-term investment in your garden’s beauty.
10. California Poppies
There is something deeply satisfying about growing California’s official state flower right in your own backyard. California poppies are naturally adapted to the local climate, which means they are practically built for success in California gardens.
Their silky orange petals and silvery-green foliage look stunning together in any sunny bed or slope.
Scatter seeds directly on the soil surface in May and press them down gently. Do not cover them too deeply because they need light to germinate.
California poppies prefer dry, well-draining soil and actually struggle in heavy clay or overly wet conditions. Once they sprout, they need very little water and care.
These poppies reseed themselves freely, so once you plant them, they tend to come back year after year on their own. They also close their petals on cloudy days and at night, then reopen in full sunshine, which feels almost like a little daily show.
Plant them along pathways, in rock gardens, or mixed with other wildflowers for a natural, carefree look. California poppies remind us that sometimes the most beautiful things in the garden are also the simplest ones to grow.
11. Bachelor’s Buttons
Bachelor’s buttons, also called cornflowers, bring a crisp, cool blue to the summer garden that is genuinely hard to find in other flowers. That vivid blue color pops beautifully against green foliage and pairs well with warmer shades like orange, yellow, and red.
They have been beloved garden flowers for centuries, and for very good reason.
Sow seeds directly in the garden in May in California for best results. Bachelor’s buttons prefer full sun and do well in average, well-draining soil.
They are surprisingly tolerant of dry conditions, which suits many California gardening situations perfectly. Thin seedlings to about six to twelve inches apart so each plant has room to branch out.
These flowers bloom from early summer into fall if you deadhead them regularly. Beyond blue, you can also find varieties in pink, white, burgundy, and lavender.
Bachelor’s buttons attract pollinators like bees and butterflies, helping the rest of your garden thrive too. They also make wonderful cut flowers that hold up well in a vase.
If you want an easy, cheerful, and historically charming flower for your California summer garden, bachelor’s buttons should definitely be on your list this May.
