As a professional gardener, these are the 5 flowers I'm planting in pots this May for bold, exuberant and non-stop summer color

Every year, as May rolls around, I can’t resist filling every available pot and trough with flowers that promise non-stop color right through summer. While perennials have their place, there’s something joyful about flamboyant annuals and tender climbers tumbling out of pots.

One plant I return to every season is Thunbergia, or the black-eyed Susan vine. I always grow this climber in small pots by the patio door, and its yellow blooms with dark centers never fail to draw in bees. No matter how many different blooms I trial each year, Thunbergia remains a firm favorite. And the best part? You can sow it from seed in May, and it will be in flower from July through until fall. Impressive, right?

So, if you want to embrace bold, exuberant and long-lasting color this summer, here are some of my favorite container flowers to plant in May. They’re cheerful, easy-to-grow and a little over the top, because why not?

5 container flowers to plant in May – my top picks

If you are looking for colorful container flowers to plant in May, you are spoiled for choice. If you fancy dwarf fast-growing flowering annuals or impactful climbers to grow in pots, there’s no shortage of options.

I always think container garden ideas should be bold; after all, pots are your chance to experiment without committing to permanent planting. Here are five of my favorite flowers that I return to year after year.

1. Chianti sunflowers

You might assume that sunflowers are out of bounds when growing in pots, with so many top-heavy varieties reaching upwards of 10 feet.

However, I usually grow one or more of the best dwarf sunflowers for pots, such as this 'Chianti Hybrid' variety seen here.

With a maroon-wine coloring, this variety is sure to turn heads, and will reach no taller than four or five feet, so it is ideal for smaller yards or even balconies.

In terms of how to grow sunflowers, position your pots in a sunny, sheltered spot, and keep them well watered and fed through the summer months.

I have known sunflowers to continue blooming late into the fall, so be sure to keep deadheading every few days to prolong their blooms, if you can.

'Chianti' sunflower seeds can be ordered now from Burpee and can be planted directly outside where they are to grow anytime during May.

Sow your seeds about half an inch deep in pots, ideally in groups of 2 to 3 seeds per container. Germination should take about 10 days.

2. Sweet alyssum

If you are seeking low-maintenance plants for pots, you won't do much better than sweet alyssum. These fast-growing tiny flowers might not pack the punch of taller varieties, but they are no less important, providing the spiller element that can cover the edges of containers.

This low-growing annual won't grow any taller than four or so inches, so it works well when paired with perennials that have more height and structure, for example, a purple blooming verbena or coneflower.

There are many different varieties available, including options with peach, red or white flowers. For a cool, blue look, try these 'Royal Carpet' alyssum seeds, available from Walmart. I always think deep purples and blues pair well and complement foliage plants in containers, such as hostas and ferns, for an understated aesthetic.

You can directly sow seeds in pots during May, ideally in a sunny position in the yard, although sweet alyssum will tolerate a little shade. If you sow seeds this month, you can expect blooms from July through to October.

3. Thunbergia

One of the easiest climbers to grow, in my opinion, is the black-eyed Susan vine, or Thunbergia alata. I have returned to this annual time and again, usually growing it in a pot near seating areas or entrance ways where visitors and passersby can admire its cheery blooms.

This quick-growing vine has a preference for full sun and can reach up to six feet in a single season, making it perfect for adding vertical color to small spaces. What's more, it is also one of the best climbers to attract hummingbirds, with its open, nectar-rich blooms.

In warmer, equatorial regions, from US hardiness zone 10 plus, this vine will be perennial, but in cooler regions, it is best to treat it as a tender annual, especially as it is so easy to grow from seed each spring.

You can buy Thunbergia alata mixed seeds from Burpee, available online. Sow them directly into containers in April or May once the risk of frost has passed. Following germination, you can usually expect flowers within 8 to 10 weeks.

And, if the black and yellow combination works for you, you could also try growing the native Rudbeckia, with live plants available to order from Walmart. These are some of the best perennials, and flower from summer through until the first frost, and can also be planted in pots too.

4. Cypress vine

The Cypress vine, or Ipomoea quamoclit, also known as the cardinal creeper, is one of the fastest-growing flowers to plant in spring. This sun-worshipper is native to the tropical regions of the Americas, so as you can imagine, thrives in the heat of summer.

What I love about the Cypress vine is its fine, fern-like foliage, which you can see above, which is perfectly complemented by red or white starry flowers that will open for much of July, August and September.

A word of warning: the Cypress vine is remarkably vigorous, and can grow up to 10 feet in a single season. Without deadheading, it will also self-seed freely, and for this reason, it is considered an invasive climber in many southern states, so be sure to check with your local government office before planting.

Cypress vine seeds are available to order from Burpee. I like to sow seeds directly into large pots in May, and you can expect a wait of around 60 days until the first flower appears.

Be sure to provide some support, either a trellis or an obelisk, for example, so the vines can latch on and grow upward. For rental units or smaller yards, try something like this movable wooden trellis and planter on wheels, available on Amazon.

5. Mexican sunflower

Tithonia, or Mexican sunflowers, are tall perennial flowers well-suited to larger and deeper containers. I have grown these on many occasions, both in hot borders full of reds and yellows, and in patio pots with bold blooms.

I would certainly recommend this option if you are planning a cut flower garden in pots this summer, with the longer stems working well for vases.

I usually sow seeds directly into deep pots or raised beds in May, when the evening temperatures are above 60°F (15°C). Germination takes about 10 to 14 days, and flowers appear in roughly 10 weeks.

Native to Mexico, you might have guessed that Tithonia thrives in full sun and tolerates drought once established, though regular deep watering will encourage more blooms.

Stake taller varieties early to prevent wind damage. I have previously grown the ‘Torch’ variety, with seeds available from Amazon, which has rich orange flowers and stands about 4 feet tall, perfect for creating height and drama in a container display.

FAQs

What flowering herbs could I grow in pots?

There are many flowering annual herbs that you can sow in pots during May. Borage, with its starry edible flowers, can be grown in pots and should take about eight weeks to produce flowers after germination. Chamomile is another good option, taking around 10 weeks to produce daisy flowers, which can be used to make a tasty, herbal tea or left to admire in pots. Both of these fragrant herbs will also prove to be popular plants for pollinators.

Remember to keep your container displays watered through the spring and summer months, as pots can quickly dry out during warm weather. Watering is best done either first thing in the morning or late in the evening, when the temperature is a little cooler.

For more garden inspiration this month, see our guide on the plants to prune in May, and keep your yard looking neat and tidy for the busy summer hosting season ahead.

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