Growing annual flowers from seed is an easy and inexpensive way to add colour to garden beds and borders. Most can be started indoors in early spring under grow lights or in a sunny window. Sow the seeds six to eight weeks before the last frost date in pots or cell packs, or direct seed outdoors in late spring. Starting them indoors gives you a head start on the flowering season but all of these annuals will still bloom by mid-summer if direct sown outdoors from mid-May though mid-June.
These annual flowers are sun-loving plants and grow best when planted or seeded in a sunny bed amended with compost. If direct sowing, don’t bury the seeds too deeply. A simple rule of thumb for seeding is to plant the seeds just two to three times the diameter of the seed. For a thin seed like zinnia, that’s only a few millimetres deep. Keep the seed bed consistently moist until the seeds germinate and are growing well; about three to four weeks.
Here are the 10 easiest annual flowers to grow from seed:
Cosmos
Cosmos have large daisy-like flowers that can be single, semi-doubled or fully doubled. They’re very pollinator-friendly and beloved by bees, butterflies, and many beneficial insect species. Depending on the variety cosmos plants can grow 60 to 130 centimetres tall so read seed packets carefully and give them room to grow. For large blooms and big plants grow ‘Sensation Mix’. For smaller spaces try ‘Xsenia’, a compact variety with carmine-rose flowers.
Zinnia
These are a popular flower for homegrown bouquets and are available in a mix of flower colours, shapes and sizes. The flowers can range in size from three centimetres to fifteen centimetres and attract butterflies to the summer garden. Standout varieties include ‘Queen Lime Red’, ‘Benary’s Giant Mix’, and ‘Candy Cane Mix’.
Marigold
Marigolds are a classic garden annual but recent breeding has resulted in a wide selection of flower colours and combinations. The three main types of garden marigolds are African, French and Gem. I love the Gem marigolds as they have feathery foliage and small brightly coloured blooms. If you want flowers for bouquets, plant African varieties like ‘White Swan’ or ‘Giant Yellow’.
Nasturtium
Carefree nasturtiums are a delight in the summer garden. I grow them along the edges of my raised vegetable beds to attract beneficial insects, but they’re also perfect for flower borders or containers. Direct seed in mid to late May for months of colour. Bonus - the flowers, leaves, and seeds are edible. My favourite nasturtiums include ‘Ladybird Rose’, ‘Bloody Mary’, and ‘Alaska Mix’.
Sunflower
Flip through any seed catalogue and you’re sure to find dozens of varieties of sunflowers to grow. Some produce just one head per stalk while others have a branching habit and yield dozens of blooms. Flower colours range from creamy white to deep burgundy with every shade of yellow and orange in between. Plant sunflowers several times during the growing season for the longest show of colour.
Calendula
Also called pot marigold, calendula plants bloom heavily from early to late summer. Their edible flowers are often used in homemade salves and ointments, or to dye fabrics. The pretty flowers come in shades of pale yellow, gold, orange and copper.
Bachelor’s button
This old fashioned annual, often called cornflower is very easy to grow. Toss down the seeds in late spring and your garden will soon be full of the novel blue, purple, pink, white, and burgundy flowers. Bees love the blooms - which are also edible and can be added to salads or used as a garnish.
Annual poppy
California poppy and corn poppy are the two main types of annual poppies. California poppies thrive in heat and are very drought tolerant. Direct sow seeds in late spring. The seed of corn poppies, on the other hand germinate best when direct sown in early spring. Cold temperatures help break seed dormancy and increase germination rates. With a bloom time that spans weeks, neither type lasts very long in the garden - but the show is worth it! The crepe-paper flowers attract bees and beneficial insects and come in many brilliant colours. Plus, they re-seed well and often return year after year.
Scarlet runner bean
This vigorous annual vine is technically a vegetable as it produces long green pods that can be harvested and enjoyed as snap beans. That said, it’s most often grown as an ornamental for the scarlet flower clusters that attract hummingbirds and bees. Let it climb fences, obelisks or arbours or use bamboo posts to make a trellis.
Love-in-a-mist
Also called nigella, this spectacular annual plant is popular in bouquets for its lacy foliage and jewel-like flowers. It’s easy to grow from seed sown outdoors in late spring and offers flowers in sky blue, deep purple, yellow, and pink. Once the blooms fade, the large, rounded seedheads also lend interest to fresh or dried bouquets.
