The care information provided in this section represents the kind of practical advice is available for all the plants in this web site if you subscribe to the monthly customized newsletter Yardener’s Advisor.
Garden phlox do best in soil that is uniformly moist over the growing season. Try to assure that they receive about 1 inch of water a week from rainfall or from your sprinkler or soaker hose system. They especially need watering during drought periods . If possible, saturate the root zone while avoiding wetting the leaves to reduce the risk of fungal disease. For information on products see the file on Choosing Watering Equipment
A general purpose slow-acting granular fertilizer worked into the soil around the plants in the spring is sufficient for phlox for the season. It provides steady, consistent nutrition over their long bloom period. Be conservative because too much nitrogen will generate excess tender foliage that is prone to disease and pests. If you mulch the soil around phlox with some organic material every year, it will contribute some nutrition to the soil as it decomposes over time. For more information see the file for Fertilizers
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Mulching discourages weeds, conserves soil moisture, enriches the soil and keeps fungal spores from splashing up on phlox flowers. Cover the soil around the phlox plants with a 1 or 2 inch layer of chopped leaves, wood chips, shredded bark, or other attractive organic material. As it naturally decomposes over the summer it will provide water absorbing humus to the soil to help see phlox through periods of late summer drought. It also contains lots of organisms that help control pest and disease problems. During the winter a mulch of chopped leaves or evergreen boughs laid over the area where phlox grow helps buffer extremes of soil temperature which may disturb plant roots. For more information see the file on Using Mulch
To prolong the bloom period, pick off faded phlox flowers promptly, before they form seeds. This will keep plants looking attractive all summer and will stimulate branching and more flowers. In a wildflower setting you may wish to allow the plants to set and spread seed. In that case leave some to develop.
Taller types of phlox may need to be staked for support in summer rain storms. Choose sturdy, straight stakes that are about 4 feet tall and insert them into the soil next to the emerging phlox stems. When the flowers mature and add weight to the plant stems, loosely tie them to the stakes with string, leaving enough slack so that the plant stems look natural. For more information see the file Staking Flowers
As is the habit with perennial plants, garden phlox roots spread over each growing season, forming increasingly large clumps. After 3 or 4 years it will be necessary to dig up the large root masses in the fall or early spring and cut them into smaller chunks of roots, each with at least with 4 or 5 shoots. At this time discard any roots that appear to be dead or diseased.
Dividing the plants in this way produces many new plants that can be established elsewhere in the yard. It also prevents the phlox from taking over the entire bed or border where they are located. In the wild garden phlox propagates itself by sowing the seed it forms on spent flower heads. Many, many young plants appear the following season. This self sowing is a nuisance in a garden bed, but is an advantage in fields and naturalized areas of the property where wildflowers are encouraged. To avoid self-sowing, cut off spent flowers.