Knowledge of the natural habitat of these plants will increase your success with them in the garden.
A cool soil with constant moisture under the light shade of deciduous trees is ideal. The use of various mulches will help to achieve this condition.
Polyantha Primrose’s Ideal Growing Conditions
Polyantha primroses are voracious feeders, and to produce show-quality umbels, the plants must not lack nourishment.
A good medium loam, with thorough bottom drainage, liberally laced with well-rotted cow manure and side-dressed in early spring with a complete fertilizer, will provide the necessary vigor.
Never allow the plants to lack water.
Under favorable conditions, the plants will form numerous crowns, quickly depleting the soil.
Proper Way To Divide Primroses
Vigorous plants should be divided immediately after flowering every 2 or 3 years.
At that time, the plant should be lifted, soil shaken from the roots, and the newly formed crowns severed or broken from the old rootstock.
The existing roots are entirely removed by cutting with a sharp knife 2 inches below the rootstock.
Reducing the roots will force the heavy anchor roots to break into many fine feeding roots.
Lastly, old foliage is best trimmed to allow new leaves to form.
The new divisions should be planted in well-enriched soil or a cold frame and constantly kept moist and shaded until roots form.
Primrose Seed Sowing
Plants in abundance may be raised from seed, germinating readily in 14 to 21 days.
To secure the strongest, heaviest-rooted seedlings, seeds should be sown in a cold frame with shaded glass or a plastic cover.
Such protection will prevent fatal surface-drying from wind before germination and conserve the necessary humidity.
Seeds may be sown as it ripens in June or July or held over until March for spring sowing.
In cold climates, seedlings are wintered in cold frames or planted out and mulched with salt hay, old cow manure, or peat moss to prevent heaving.
Pest Control Methods
Foliage should be maintained in a vigorous state throughout the growing season.
Black spots, surrounded by a yellow area, may eventually cover the entire leaf, reducing the plant’s vitality.
A combination spray of Bordeaux mixture with lead arsenate, applied during the season, especially in early spring, will control this bacterial leafspot and all chewing insects.
In addition, green aphids, red spiders, and two-spotted mites may be controlled with regular spraying of Isotox.
Complete control against insects is the best insurance against several little-known but deadly virus infections since insects carry the virus from one plant to another.
Uses Of Primrose Planting
An imaginative gardener will find many places in his garden suitable for planting polyantha primroses.
Of course, they are always lovely when used as fillers for beds of spring-flowering bulbs, but they are also effective when massed in semi-shady locations with fern fronds or broad-leaved backgrounds of evergreens.
The gnarled branches of an old apple tree are complementary when blossoming and afford cooling shade from the hot summer sun when the leaves have formed.
If you are a patio gardener, pot several dozen polyanthus and group them with a suitable backdrop for a dramatic pictorial effect.