How to Grow Spiny Phlox

Growing Spiny Phlox From Seeds

• 1

  Gather seeds from an existing spiny phlox plant in late summer once the capsules dry out and begin to split, or acquire seeds from a native plant nursery. Store the seeds in an airtight container until mid-March of the following year.

• 2

  Fill 3-inch peat pots with a mixture of two parts moistened garden soil and one part fine sand. Firm the soil in each pot. Set the peat pots on a tray to make them easier to handle.

• 3

  Sow two spiny phlox seeds in each peat pot. Press the seeds 1/4 inch deep into the soil and sand mixture. Spread a thin layer of fine sand over the seeds.

• 4

  Set the peat pots outdoors against a south-facing wall with full sun exposure. Avoid placing the pots in the shade since the soil will take a very long time to dry out and the seeds might rot.

• 5

  Water each pot only when the top inch of soil feels dry to the touch. Apply just enough water to lightly moisten the top inch of soil.

• 6

  Watch for germination after seven days. Remove the weaker of the two seedlings from each pot once they grow to 2 inches in height and have a set of true leaves.

• 7

  Transplant the spiny phlox seedlings into a sunny or partially shaded bed once they grow to 4 inches in height. Plant them in full sun in mild climates and partial shade in warm areas corresponding to U.S. Department of Agriculture hardiness zones 8b and above.

Growing Spiny Phlox From Cuttings

• 8

  Grow spiny phlox from cuttings in late spring around early May. Wait until all the flowers have faded from the plant before striking cuttings from it.

• 9

  Prepare a rooting pot for the spiny phlox cutting before gathering it. Fill a 3-inch peat pot with three parts fine sand and one part garden soil. Moisten the soil with 1/8 cup of water.

• 10

  Select a 2- to 4-inch-long portion from the tip of a spiny phlox stem composed of new growth. Pinch the cutting off between two sets of foliage.

• 11

  Strip off the foliage from along the lower half of the stem cutting. Dip the leafless end of the stem cutting into 0.3-percent IBA rooting hormone.

• 12

  Insert the hormone-treated end of the spiny phlox cutting into the prepared rooting pot. Press it in until the lowest sets of foliage are approximately 1/16 inch above the surface of the soil.

• 13

  Set the potted spiny phlox cutting outdoors under light shade. Avoid exposing the cutting to direct sunlight since the leaves will dehydrate and the cutting will fail to root.

• 14

  Water the soil mixture to keep it moderately moist at a depth of 1 inch. Let the soil dry out slightly before adding more water.

• 15

  Check for roots in 25 days by carefully trying to lift the cutting from the rooting pot. Plant the spiny phlox cutting and its peat pot directly into a garden bed two weeks after rooting.