Not all flowers are destined for the garden bed or landscaping borders. Transplanting flowers into large outdoor planters is another possibility. Planters bring bright blooms onto patios, decks and balconies or are used to frame entryways or sidewalks. Transplanting into planters is very similar to transplanting directly to the garden bed, except that more care must be taken after placing the flowers in the planter to ensure they continue to thrive and bloom. Fill your planters with either annual or perennial flowers, or a mixture of both.
Choose flowers that require the same amount of water and moisture retention, sunlight and fertilization. Compare plant tags or seed envelopes to find the best matches if combining more than one type of flower in a planter.
Harden off the flower transplants seven days before your planned planting date. Set out the young plants in an area out of direct sunlight and shielded from strong winds for two hours the first day. Continue setting the the flowers outside, increasing the time by one hour each day and moving them closer to the planter area each day.
Check the planter for drainage holes---it should have at least two for smaller planters and four or more for larger planters. Place a 4 inch layer of gravel in the bottom of planters that don't have drainage or drill holes in the bottom of the planter.
Fill the planter with well-draining potting soil. Mix your own by combining 1 part compost, 1 part peat moss and 1 part perlite. Fill the planter to within 2 inches of the rim.
Mix a slow release balanced fertilizer with the potting soil. Follow label instructions for exact amount to use, as this differs among manufacturers.
Grasp the flower plants by their stems near the soil surface. Pull them out of their containers. Loosen the roots on the bottom of the plant gently using your fingers.
Plant the hardened off flowers in the planter to the same soil depth they were in their original containers. Gently firm the soil around them with your hands. Spacing depends on the plant variety; see the seed envelope or or plant label for spacing instructions.
Water the planter until water comes out the drainage holes in the bottom or until the soil is evenly moist. Keep the soil moist at all times, watering whenever the soil surface begins to feel dry.