When to Plant Flower Seeds

The timing of indoor planting is really up to you… as long as the seedlings are mature enough before you move them, you harden off your seedlings before moving them and you don’t transplant into your garden before the last frost, you should be okay.

Perennial bulbs have some special planting requirements. See our How, Where and When to Plant Flower Bulbs page (coming soon) for more information.

Learning how to plant flower seeds outdoors is a different story, and its timing depends on whether your flower is an annual or perennial variety…

Perennial flowers
Annual flowers

Perennial Flowers: When to Plant Perennial Flower Seeds Outdoors

Perennial flowers should be planted from seed at one of two times: early spring or late fall. Planting in early spring will ensure that your plants’ roots have time to grow big and strong enough to survive the winter.

But late fall? Won’t that kill my plants before they have a chance to grow? The seed coating provides all of the protection the plants need, and the seeds will remain dormant until spring rolls around.

Planting in late fall serves another purpose as well: many perennial seeds need a moist cold spell in order to germinate (a process called “Stratification”). Accomplishing this for spring-sown perennials requires more involvement on your part.

Although learning how to plant flower seeds in the spring is more difficult, it can be done. You’ll need to first mix your seeds with vermiculite and evenly moisten the mix to the point that it feels like a wrung-out sponge. Put the mixture in a sealable container or bag and place in the refrigerator for 2 ½ to 3 months. Obviously you’ll need to time this with your planned planting date.

Annual Flowers: When to Plant Annual Flower Seeds Outdoors

Annual flowers should have planting times that coincide with their individual cold tolerance…

Hardy flowers can be planted as soon as the soil has thawed enough to be worked and as long as you know your soil temperature won’t drop below 25 degrees F (-4 C).
Half-hardy flower seeds should wait until the ground is consistently warmer, although a light frost or two will most likely be okay.
Tender flowers shouldn’t be planted until all danger of frost has passed. Anything below 40 degrees F (4 C) and they could be in trouble.
See our Flower Planting Guide for cold-tolerance levels of each flower.

If you want to get your half-hardy or tender annual flowers into the garden sooner, start them indoors (discussed further down the page) and transplant them into the garden when temperatures are more agreeable.

Source: http://www.growinganything.com/how-to-plant-flower-seeds-planting-flower-seeds.html