Fastest Growing Flowers: Hardiness Zones Explained

Newly-landscaped spaces can look quite dull while you're waiting for plants to blossom and add much-needed color and vitality.

Not all seeds and bulbs take an age to germinate and grow, especially if you pick the best ones for your climate and soil conditions.

Most annual plants need 95-days to get from seed to the flowering stage. Many of our featured ones begin flowering from as early as 60 days from planting.

To give your flowers the best possible growth conditions, ensure the soil is fertile and has lots of organic matter mixed through it. Adhere to their climatic and positioning requirements, be patient, and don't overwater.

Beginning the seed growing process indoors, beneath lights, they have the best chance of reaching maturity when transplanted outdoors.

USDA Hardiness Zones

The United States Department of Agriculture divides the country into 13 zones depending upon their annual extreme minimum temperature. Each numbered region denotes its geographic hardiness zone, encompassing its range of climatic conditions.

Every plant has a designated range of zones that best suit its growing needs.

Fastest Growing Flowers

Blue Hydrangea – Hydrangea macrophylla "Nikko"

hydrangea macrophylla

Most people recognize the large purplish-blue rounded heads of the hydrangea. They are commonly used in large beds and borders as they grow rapidly, reaching maturity within three years. By this time, with regular watering and maintenance, they become both 6-feet wide and high.

They are deciduous plants that flower every summer; each has multiple long-lasting blooms.

Hydrangea changes color, reflecting the pH of the soil.

  • Best suited to zones 6 – 9

Oleander – Nerium oleander

nerium oleander

Most of us will have caught a glimpse of oleander growing in the wild. It is a fast-growing, evergreen shrub that handles tough conditions well. It doesn't exactly thrive on neglect but can survive drought and needs less than 2" water per week.

It flowers prolifically from spring through fall. Colors vary from yellow, white, pink, and red, and they all emit a fragrant aroma.

Oleanders grow at a rate of 2-feet per year, especially when planted in salty soil and left in full sun. They reach heights of 20-feet, spanning 10-feet when fully-mature.

They don't fare well in frosty conditions and, if possible, taken indoors.

As pretty as they are, oleanders are toxic to pets and humans. Consider planting them to create borders away from the house, and always wear gloves when pruning.

  • Best suited to zones 8 – 10

Nasturtiums – Tropaeolum

tropaeolum

Nasturtiums come in multiple varieties, including bush, dwarf, and trailing. Whichever you opt for, be assured of fast ground and wall cover, in pots or directly into the soil.

They come in multiple colors; not only do they brighten up the yard but also add a splash of color and flavor to a dinner plate. Both their leaves and petals are edible, adding a peppery taste to salads.

Each plant has multiple brightly colored flowers; the Peach Melba variety that flowers from early spring through to the first frost, or Strawberries n Cream that blooms in June and hang around until early winter.

If you're looking for fast-flowering climbing plants, consider the Jewel of Africa nasturtium. It grows to heights of 6-8', if left unattended, it takes over very quickly.

Plant nasturtiums in fertile soil after the last frost; they bloom best in full sun although they flower in areas of partial shade, although in less abundance.

  • Best suited to zones 3 – 10

Sweet Alyssum – Lobularia maritima

lobularia maritima

Sweet alyssum is worthy of consideration when looking to create a carpet effect of low-growing pastel shades in a limited time.

It is a cool-season flower that is safe to plant out as soon as the sign of any frost passes. From seed, it reaches maturity within 2-months, resulting in an abundance of delicate flowers and a soft scent that grows stronger during the evening.

In frost-free climates, alyssum grows and blossoms through fall and winter. It prefers a mixture of full sun and partial shade; extreme heat causes the pinks and purples of the petals to fade.

Their greenish-gray hairy leaves combined with a myriad of brightly colored flowers attract many insects; hoverflies and bees in particular.

  • Best suited to zones 7 - 11

Calendula – Calendula officinalis

calendula officinalis

Otherwise known as the pot marigold, calendula provides flashes of rich yellows and golds that stand between 12” - 24” tall.

They grow quickly, from seed or cutting, and their broad leaves easily fill empty bedding areas. They bloom from May through to early fall; remove dead heads to see them quickly replaced by new flowers.

Calendula is a short-lived perennial plant in warm climates. Most gardeners grow them as annuals in flower beds and pots. They prefer full sun with partial shade and fertile, well-drained soil. However, they are relatively adaptable to most conditions and tolerate poor soil.

Don't overwater any of the many species of calendula; they won't thank you for it. Water until they are established and then infrequently. With regular dead-heading, the fast-flowering rewards are huge.

  • Best suited to zones 9 – 11 (perennial) 2 – 11 (annual)

Johnny-jump-ups – Viola tricolor

viola tricolor

If these tiny yellow and purple flowers look familiar, that's because they are miniature pansies. They are members of the same family, along with many other species, including violas.

Plant them as seeds, within 10-days you will see signs of germination. By early spring they will be a flurry of flowers, far more than the larger pansy holds.

Johnny-jump-ups like plenty of sun but manage to flourish in partial shade. They prefer moist soil, especially with lots of organic matter mulched through it.

Their fast growth and riotous colors make the ideal choice to sit beneath trees or fill in gaps between shrubs.

  • Best suited to zones 3 – 9

American Giant Sunflower – Helianthus annuus

 helianthus annuus

Sunflowers are striking plants, but the American Giant is probably one of the most imposing. When fully mature, it reaches 5-meters tall and has a thick, sturdy stalk that allows it to be free-standing.

They make wonderful screens and inject a shock of yellow above the height of most other plants.

It is one of the fastest flowering plants; it takes just 70-100 days to achieve full maturity. It occurs at various stages of the year, depending on when the seeds were planted. The dramatic display is usually on-show between July and October and lasting for 8-weeks.

When the last frost has cleared, sunflower seeds will germinate when placed directly into the soil. Seedlings appear within 7-10 days, closely followed by leaves. When each plant has 2-leaves it is time to thin them out to allow for plenty of growing space.

As their name leads us to believe, sunflowers adore full sunshine. They thrive in well-balanced soil in open space where they will tower above other plants, leaving them overshadowed.

American Giant sunflowers create impactful hedging in a few, short weeks, turning the smallest backyard into a sun forest.

  • Best suited to zones – 2 and above (including those with short summers)

Annual Phlox – Phlox maculata

phlox maculata

Phlox is a small, annual plant that adds many colors and a sweet fragrance to flower beds. They grow to a height of 6 – 12" and look best when planted in clumps.

Consider planting them in early spring, even before the last frost of the season. The young seedlings are tolerant and survive light frosts. If you live in a warm climate, hold back until the fall. By late spring, phlox begin to bloom en mass, in numerous colors; pastel shades of pink and violet, more vivid reds and oranges.

Dead-heading extends the flowering period, resulting in a blanket of color through until the end of summer.

They like partial sunshine and thrive in well-drained soil with average fertility.

  • Best suited to zones 2- 10

Final Thoughts

Good soil preparation is paramount to encourage fast-growing flowers. Fertile soil with added organic matter suits fast-growing plants. When positioned to receive their desired amount of sunlight, your only duty is to keep them hydrated. Watering deeply and infrequently promotes a good root network and fast growth.

Finally, remain patient and enjoy the fruits of your labor. Even before flowers reach full maturity, they create a beautiful landscape.

Annette Marsh
For the past twenty years, Annette has allocated much of her free time towards gardening and landscaping related tasks; Planting flowers and trees, weeding, pruning, mulching, mowing, constructing ponds and various other structures, as well as growing and maintaining a vegetable garden.

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