When to Fertilize Phlox

Phlox are colorful flowers that are native to temperate North America. The name Phlox is Latin for a flame-colored flower. There are 67 species. Different varieties, that botanists sometimes call cultivars, produce tiny flowers that are white, blue, shades pink, yellow or shades of lavender and purple. The flowers come in clusters from the spring through summer and into fall. Some species form low mats a few inches tall, others can grow more than a yard-and-a-half tall. The timing for applying fertilizer is not complicated.

General Needs

The phlox that grow in most gardens are perennials, meaning they go dormant in the autumn and return in the spring. They grow back from root stock. You don’t have to replant them each spring. They like soil that is well drained, plus some sun and some shade.

Although you can fertilize phlox, it is not essential. It’s good to incorporate generous amounts of nutrients into the soil before planting them, especially if it’s sandy soil. You can use compost, peat moss or manure.

Understanding Fertilizers

To pick the right commercial fertilizer, you need to understand the numbering system on the package. The first number is the ratio of N, nitrogen that is needed for the growth of the plant above the ground. The second number is P, phosphorous that is needed to grow strong roots. The third number is K, potassium that is needed to make plants strong, able to resist disease, and able to survive for long periods without water.

General Needs of Perennials

Perennials ordinarily need a fertilizer with low amounts of nitrogen. If a perennial has too much nitrogen, it will produce fat stems and huge leaves instead of flowers.

A soil test will tell you if your soil is lacking in nitrogen, phosphorous or potassium. If your soil is not tested, you should select a fertilizer with a lower amount of nitrogen or one that has balanced numbers.

When to Fertilize Phlox

It is good to fertilize phlox with a slow-release fertilizer. Do this once in the spring when the phlox begins growing again and once in late summer just before they go dormant. You also can fertilize once just before the blossoms appear.

You should mulch your phlox. To fertilize, follow the directions on the package. Pull back the mulch and sprinkle the fertilizer around the plants. Replace the mulch and water the plant thoroughly.

Tip

While phlox do not require large amounts of fertilizer, you should avoid planting them in the shade of trees. Tree roots rob phlox of the moisture and nutrients they need to flourish and provide their colorful blossoms. For the same reason, don’t plant them near hedges and large shrubs.