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Idaho Enterprise

Tips for Planting Flowers

When do you plant flowers in the garden? It depends! Is it a perennial flower, annual flower, or bulb? Is it frost-sensitive or not? As with vegetables, there’s a right and a wrong time to plant your beloved blooms. Here’s when to start seeds and when to transplant young plants outdoors.

Different plants need a different amount of lead time before they are ready to transplant into the garden. Starting too soon can result in a weak, lanky plant, while starting too late can give you one that is just not ready for the outside world—both will struggle to survive! Here’s what you should take into consideration before planting.

Know Your Frost Date

Before you even think of starting seeds, you must know your area’s spring (and fall) frost dates. Planting schedules like the one below or our Vegetable Planting Calendar rely on frost dates to determine when it’s safest to ultimately plant outdoors since young plants are more susceptible to a freeze.

When to Plant Perennial Flowers

Perennials are plants that are capable of surviving two or more years. While they may die back to the ground in winter, their roots survive underground and produce new foliage as the increased light and warmth of spring arrives. Most perennials will bloom in the same year that they are planted, while others may need to spend time becoming established first (particularly if planted later in the growing season). 

Start Seeds in the Spring

Some perennials can be challenging to start from seed, but most are fairly easy to grow and make for an inexpensive way to fill up a new flower bed. Some seeds will need a period of cold temperatures before they will germinate and may also take a longer time to germinate—3-4 weeks is not unusual—so they should be started earlier than others. Follow the instructions given on your seed packet.

Plant Mature Perennials in the Fall

If you’re planning on adding mature perennial plants (such as those bought from a nursery) to your garden, the best time to plant is in the fall, so the cold temperatures and moisture that come with winter stimulate germination. Plant them at least six weeks before your first fall frost date in order to give them time to settle in before winter. Roots will still grow while temperatures are in the 40s (Fahrenheit).

When to Start Perennial Flower Seeds

Flower

Start Seeds Indoors (Weeks Before Last SPRING Frost Date )

Plant Outdoors

Anise Hyssop

8-10 weeks

On last frost date

Asclepias (Milkweed)

10-12 weeks

1-2 weeks after last frost

Catmint

8-10 weeks

On last frost date

Columbine

8-10 weeks

On last frost date

Coreopsis

8-10 weeks

On last frost date

Daisy

10-12 weeks

1-2 weeks before last frost

Delphinium (perennial)

10-12 weeks

1-2 weeks before last frost

Dianthus

10-12 weeks

1-2 weeks before last frost

Echinacea (Coneflower)

8-10 weeks

On last frost date

Foxglove (Digitalis)

10-12 weeks

1-2 weeks after last frost

Gaillardia

8-10 weeks

On last frost date

Helianthus

8-10 weeks

On last frost date

Heliopsis

10-12 weeks

1-2 weeks after last frost

Hibiscus

8-10 weeks

1-2 weeks after last frost

Hollyhock

8-10 weeks

On last frost date

Monarda (Bee Balm)

8-10 weeks

On last frost date

Phlox (perennial)

10-12 weeks

1-2 weeks after last frost

Rudbeckia (Black-Eyed Susan)

8-10 weeks

1-2 weeks before last frost

Thyme

8-10 weeks

On last frost date

Viola

8-10 weeks

1-2 weeks before last frost

Yarrow

8-10 weeks

On last frost date

 

When to Plant Spring and Summer Bulbs

Planting bulbs is another lovely way to add seasonal pops of color to your garden. We divide bulbs into two main categories: spring-flowering bulbs and summer-flowering bulbs.

  • Spring-flowering bulbs are those that bloom from early spring to early summer. Included in this category are flowers like tulips, crocuses, and daffodils.
  • Summer-flowering bulbs are those that bloom from early summer to early fall. Included in this category are flowers like gladiolus, dahlias, and cannas.

Generally speaking, spring-flowering bulbs should be planted in the fall (a few weeks before the first frost), while summer-flowering bulbs should be planted in the spring (a few weeks after the last frost). Why? In many cases, summer flowering bulbs are not hardy enough to survive winter outdoors, while spring flowering bulbs may actually need a period of colder weather to trigger their spring blooms. There are exceptions, of course! Hardy perennials that flower in the summer, like daylilies, can be planted in the spring or fall.

What Makes a Bulb a Bulb?

Not all “bulbs” are actually bulbs! A true bulb is a specific type of underground storage structure—think onions, tulips, and daffodils. Many popular “bulbs” are actually other types of structures, like corms (gladiolus), rhizomes (irises, daylilies), and tubers (dahlias). However, most gardeners simply refer to this entire category of plants as “bulbs” to make things a little easier!

 

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