Growing Ornamental Plants: Growing Polyanthus

Latest Update 12th April 2020.

Growing Polyanthus

Polyanthus begin flowering in late winter and continue for several weeks into spring. They are best planted in autumn under the canopy of a deciduous tree. Here they enjoy full sun during the growing season and get the tree's shady protection when dormant in summer.
Remove spent flowers and their stems during their growing season in the cooler months to maintain a continuing supply of new flowers.
As they die back after flowering finishes in spring, protect them from the hot and dry conditions of summer with mulch.
They will survive summer, provided the soil stays moist but not wet, and the soil is mulched to protect them from excessive heat. They are best grown in raised garden beds, and not watered during summer, but they will need plenty of water when they are ready to end dormancy in late autumn.

Details.

Growing Conditions.

Polyanthus grow well in healthy organic soil providing it is well drained.
They will rot if the soil is wet during dormancy in summer.
They need good sun during the growing season in late autumn through to early spring.
Minimise soil disturbances to maintain a natural soil structure.
They can be damaged by persistent or severe frost, but in a warm temperate climate, this is not an issue.
They can be attacked by fungal diseases if their foliage stays wet for too long. Aerated compost tea is very effective at controlling these diseases and drip irrigation rather than overhead watering helps.

Feed the Soil.

Prepare a new bed for young polyanthus in late summer by removing old mulch and other organic waste, and covering the soil with a 60mm layer of homemade compost.
Cover this with fresh straw mulch and leave it for 4 weeks to build up worm and microbial activity.
Remove the mulch ready for planting in autumn.

Growing Instructions.

Plant new polyanthus 200 to 300mm apart (depending on variety) in early autumn. Water them in well with dilute seaweed extract and keep the soil moist throughout their growing season.
In spring after flowering finishes and foliage begins to die back, remove old mulch, fallen leaves and other decaying organic material from around the polyanthus and cover the soil around them with a 60mm dressing of home made compost.
Cover the compost with fresh straw mulch. The plants will push through this when they begin to grow again in late autumn.
Spray their foliage with aerated compost tea once a month during the growing period.

Organic Pest Control.

My polyanthus have been pest and disease free for many years. Because they grow through winter, there is very little insect activity, but they can be effected by the following:-

If you can protect your raised bed with self adhesive copper tape, the slugs and snails will be kept out of the bed.
If not, use organically approved iron based snail pellets. Just scatter a few thinly amongst your plants. You should only need to use a small number of them.

Regular foliar sprays of aerated compost tea boost the natural defences of plants by colonising leaf surfaces with beneficial microbes. These microbes defend the plants against airborne pests and diseases.

Similarly, proper soil preparation including regular applications of home made compost boosts the community of beneficial microbes, which defend the plants roots against plant pathogens.

Growing Ornamental Plants