Phlox paniculata

The perennial Phlox paniculata is a member of the Polemoniaceae, and originates from North America. Phlox is an excellent filler for a bouquet with a nice fragrance. Bartels Stek can offer Phlox varieties perfectly suitable for cut flower production.

Overview of Growing Phlox

For growing phlox a temperate climate with cool nights (nights 12-15 o C) is preferred. Daytime temperatures should not average above 25-27 o C. Production responses positively to high light intensities.
Crop development can be expected according to schedule:  3   weeks – first pinch; 16 weeks – flower; apply long days immediately after harvest if not already in long days, then flowering will occur again 13 weeks later. Repeat as needed.


Put the crop support netting on the ground before planting, to make planting easier. Make small holes in the ground in which the plugs fit nicely, to get an optimal contact between plug and soil. Plant a little deeper as the plugs are tall. Do not damage the root system by pushing the plugs in the soil.
Plant 16 plants per net square meter outside or 24 plants per net square meter in a greenhouse. This will result in 60-100 stems per m² after pinching. According to the climate there is always some fine-tuning to be done to get the optimum balance between quality and quantity.

Single Stem Production

For single stems, 60 rooted cuttings are planted per square meter. Placing nets before planting makes planting more easy. Plant deep enough, the plug has to be covered by soil. To spread the flowering every two weeks a block is planted, don’t pinch. This allows you to program the phlox production in a continuous weekly production.

Soil and Fertilization

Phlox paniculata requires a particularly well-drained soil. Phlox is very hardy, but also very vulnerable to water logging soils, especially during winter. Preliminary soil analysis is recommended.
Take care of a sufficient basic fertilization (EC soil minimum 1.8) and humus percentage (5-10%).  During the cultivation phlox needs a lot of fertilization. When fertilization is given through irrigation it is advised to keep the EC at 2.0 in the water. When solid fertilizers are used, give 25 kg 12-10-18 per 100 m2 every 8 weeks.
The leaves of phlox show a shortage or oversupply of elements right away. Yellowing at the leaves mostly point to lack of nitrogen (N).  Ensure basic fertilization.
An even distribution of water is very important. Give frequent water after planting as the first roots establish in the upper (5 cm) part of the soil. Because of the very small root system it is essential to give overhead irrigation, by using micro jets for example, until plants are 30 cm tall. Be careful not to over-irrigate in the generative stage; too much water will cause a vegetative reaction, the side shoots will start overtaking the central stem. Beware of phlox’s vulnerability to excessive watering.


Phlox needs a daylength of at least 16 hours, 18 hours is recommended. Daylength extension can be done by normal cyclic lighting with bulbs, like mums. Give at least 10 minutes per half hour light, use 15 watts per m2. Start with the lighting immediately after planting or cutback/pinching, and continue until flowering.


Pinching needs to be done as soon as possible after the plants have well established. The right time for pinching is when the majority of plants in a block are starting to elongate. Leave at least 4 leaf pairs or leaf buds on the plant. Pinch a whole block at once to get uniform regrowth. Single stem production, don’t pinch !


Harvesting can be done 3 to 4 months after planting, depending on the climate, time of year and variety. The stems should be harvested when at least one flower is open. When you single stems, harvesting can be done after 14-18 weeks.
Leave about 5 cm on the plant for a good regrowth. Under good outside conditions or in a greenhouse one may expect a second flush after about 3 months. Phlox can be grown a second year. A third year is not recommended.

Postharvest Treatment
Phlox is sensitive to ethylene damage and bacterial growth.  Prevent dropping of the flowers by treating stems with 2 ml Florissant 100 per litre water directly after harvest. Minimum treatment is 4 hours. The solution can be used as long as it is clean (up to one week). To reduce bacterial growth put stems in a bucket with 1 tablet Florissant 500 per 3 litres water. The stems can stay in this solution until they are to be sold or shipped.