Growing flowers from seed is one of the best ways to stretch your flower budget but requires a little extra know-how on your part. Many flowers--both perennial and annual--can be started inside four to six weeks before the chance of frost has passed with little more than some good-quality soil, a sunny window and regular, gentle watering. Check seed packaging for specific instructions for your plant choice as some seedlings are too fragile for transfer and should be sown after the chance of frost directly outdoors. Some popular flowers best started from seed indoors include marigold, petunia, impatiens, zinnia, columbine, coreopsis, hibiscus, lobelia and purple coneflower.
Fill your trays or peat pots with a good-quality seed-starting potting mix. Seed-starting mix is a light-weight mix usually composed of vermiculite, sphagnum peat moss, limestone and humus, and fortified with a proper nutrient mix of nitrogen, phosphorus and potassium. Make-your-own recipes are widely available from garden centers, agricultural extension offices and online.
Plant two or three seeds in each pot or in a trench line if using trays. Follow planting instructions for your particular plant selection as per the packaging for forcing seeds indoors. Different plants have different needs as to how deep the seed should be planted. Place peat pots in a container such as a gardener tray or even a cake pan to collect water and protect surfaces.
Water gently with warm water.
Cover with plastic or commercial "dome" to maintain the proper humidity level needed for germination. Germination, or when the seed begins to sprout, also varies per plant, sometimes in just a few days up to a few weeks.
Place your covered tray or pots in a warm place out of direct sunlight until seeds begin to sprout. Most seeds prefer a nighttime temperature of 55-65 degrees F for proper germination though some cold-temperature plants such as snapdragon, sweet pea and pansies like it about 10 degrees colder.
Move to direct sunlight and remove cover once seedlings are starting to sprout, especially when the tallest ones start to touch the plastic. South-facing windows are the preferred location to receive the most sunlight. Consider grow lights if a sunny location is not available.
Thin seedlings to one per pot, choosing one in the middle that looks strong, to remain. Seedlings planted in trench trays should be carefully dug apart and moved to larger pots to allow for room for root growth.
Keep seedlings moist and lightly fertilized as they grow, allowing for the most light possible.
Harden off older seedlings by moving outdoors to a covered location once the threat of frost has passed for a couple of weeks before planting in beds or containers. Cold frames are an excellent tool for hardening off plants. Bring inside if temperatures are to go below 45 degrees F or if the wind is to be strong.
Plant in beds or containers once the threat of frost has passed, following spacing suggestions as recommended per the packaging for your plants.