Phlox is a beautiful groundcover perennial that spreads rapidly and can grow to be 6 to 8 inches tall. A hardy plant that grows especially well in zone 4, phlox gives a very pleasant 1 inch bloom with a five petal arrangement. Many gardeners sow the phlox right into the soil so it will retain its hold on the landscape. However, if you do not have a lot of land for a flower garden, or just want to have a low growing flower near, you can successfully grow phlox in a container.
Step One - Start Your Seeds Early
Growing plants in a container is a great way to easily move plants around your yard, add to the decorative touch of your window, or add flowers to your deck, patio, or porch. However, just because they are in pots does not mean that you can plant them at any time. Phlox is a plant that needs a lot of direct sun. They go dormant in the winter time, so planting them in the late summer, or fall will not produce any plants.
Start your seeds early. About six weeks before the frost goes out of the ground, you should plant them in small pots with a light covering of potting soil. Water them, then leave them in a plastic bag until they begin to sprout.
Step Two - Place on Sill
Once the sprout begins to come out, which usually takes about 4 to 5 weeks, take the pot out of the plastic bag and give it some all-purpose fertilizer and water. Set the new plant on the windowsill where it can get plenty of full sunlight.
Step Three - Transplant to Flower Box
After the last frost, the soil temperatures should be warm enough that the young phlox plant can tolerate the outdoors. Phlox does not do well with highly fluctuating temperatures or weather that consistently dips below 20 degrees.
Get a flower box that will handle at least three to four plants. Transplant your phlox to the box and keep the plants at least 6 inches apart for them to grow efficiently. Do not try to overcrowd the box. Put in an all purpose potting soil and water. It is also alright to use some water soluble fertilizer at this point, as it will need some added nutrients to keep its strength for blooming.
Step Four - Transplant to Large Container
If you want to keep your phlox near your deck, patio, or other areas for easy viewing, you should put them in a long container pot. Phlox is a creeping groundcover that likes to stretch out. The low growing blossoms will look great lined up in a long line. Keep the vines, and leaves pruned back for only the blossoms.
Fill the container with potting soil and mix in some all purpose fertilizer. Transplant the young flowers into the pot, again at least 6 to 8 inches apart. After they grow a while they will cover the rest of the space quickly. Water the soil and keep it moist.