While most of us have come to associate primroses as some of the first flowers of spring, this diverse genus can be found in bloom from midwinter right into early summer. Those early-blooming Polyanthus can be difficult to keep from year to year but the perennial forms are quite reliable, given optimal care and regular division. What is not in doubt is the vast spectrum of flower colour and form that this genus provides, so I thought we would take an in-depth look at primulas.
Polyanthus – These are your supermarket variety primulas which can be found at every garden centre and corner store starting in late January. They are complex hybrids originally thought to be a cross of Cowslip (P. veris) and the common primula (Primula vulgaris) which gained popularity due to their showy central blooms that come in a multitude of colours, including picotee and veined varieties. While most of us take these relatively inexpensive plants for granted, few flowers provide such a bold winter display for those early mixed containers and hanging baskets. If possible, keep these under cover as the rain quickly spoils the flowers and the foliage is quite susceptible to fungal problems, as they have been grown with heat out of season. Also, you’ll find that many of the yellow varieties still retain a sweet fragrance on those rare warmer days.
Primula veris, Polyantha 'Orion Frost Rose', Primula veris 'Sunset Shades'
Common Primrose – Primula vulgaris is a staple of the English cottage garden and an invaluable perennial for open shade exposures. Many of the double forms such as ‘Miss Indigo’, ‘Quaker’s Bonnet’ (pink), ‘Corporal Baxter’ (red), ‘April Rose’, ‘Blue Sapphire’ and ‘Ken Dearman’ (apricot) have been with us for decades now. Newer hybrids such as the Belarina Series bring us better vigour and subtle colour options in such hybrids as ‘Nectarine’ and ‘Pink Champagne’. There are also Jack-in-the-Green types like ‘Dawn Ansell’ (white) with sepal collars at the base of the blooms as well as those with dark foliage, including ‘Kennedy Irish Innisfree’ (ruby red flowers over bronzed leaves). Perhaps the most interesting cultivar ‘Francisca’, has local origins; as this frilled green-flowered variety with a yellow eye was first discovered by plantswoman Francisca Darts in a Surrey BC traffic island. This group also includes the modern semi-double Primlets (sometimes listed as P.acaulis) which are available early season in a variety of colours.
Primula vulgaris 'Belarina Nectarine' , Primula vulgaris 'Blue Sapphire', Primula vulgaris 'Corporal Baxter', Primula vulgaris 'Dawn Ansell', Primula vulgaris 'Francisca', Primula vulgaris 'Kennedy Irish Innisfree', Mixed Primlets, Primula vulgaris 'Belarina Pink Champagne'
Candelabra or PomPom Types – This category includes a number of species with tiered or balled flowers held on a stem above the crown. The latter includes Primula denticulata or Drumstick primula which is generally purplish-blue in colour but also comes in pink and white forms. The slightly more sculpted Himalayan Primrose (P. capitata) bears violet-blue blossoms dusted in silvery-white. Moisture loving Primula japonica and P. bulleyana (including the subspecies bessiana) bring a riot of colour (pink, yellow, white, gold and crimson) to any pond-side garden with their multi-tiered flowers and both are USDA zone 5 hardy.
Primula japonica 'Miller's Crimson', Primula japonica 'Apple Blossom', Primula japonica, Primula bulleyana, Primula denticulata
Juliana or Wanda Hybrids – In my opinion there probably isn’t a more bulletproof primula than the old-fashioned ‘Wanda’. It is an RHS Award of Garden Merit winner (1919) and I have seen its purple blossoms grace many a garden that has been long abandoned, so it can take care of itself. Newer Wanda hybrids bring us the full colour range of red, raspberry pink, white, violet and bright yellow. This early-blooming cross of Primula juliae and a crimson form of P. acaulis is USDA Zone 3 hardy and grows very tight to the ground.
Species – With over 500 species within the genus, I’ll just touch on a couple of the most common as well as a few odd ducks. We’ll start with the traditional English Cowslip (P. veris) with its umbels of fragrant bright yellow blooms (‘Sunset Shades’ are orange to coppery-red) that herald the arrival of spring. The tender Fairy Primrose (P .malacoides) can often be found as a houseplant in the early season with its massive trusses of pastel blossoms, but at USDA zone 8 it cannot be overwintered outdoors here. The waxy-leaved Auriculas are often grown in pots by collectors who admire the vast array of colour and flower form, but this alpine species requires sharp drainage and often rots in our wet winters. The ‘Gold-Laced Group’ of primula are just as showy but much more tolerant of average in-ground conditions. Primula vialii or the Chinese Pagoda Primrose has unusual poker-like blooms of purplish-pink that are red in bud; these need regular dividing as this species is rather short-lived.
How to Take Care of Perennial Primula
Division – Perennial primulas require dividing, every 3 to 4 years, in order to maintain their vigour. You can split them immediately after flowering or in early autumn and pass on any extra plants to fellow gardeners.
Irrigation – Most perennial primula get their necessary watering from Mother Nature, as they tend to bloom during the spring rains. However, for the best display the following year; make sure they are not allowed to dry out during the summer heat.
Fertilization – Fertilize in early spring using an all-purpose perennial fertilizer, being careful not to allow any of the granules to get caught in the crown, where they will burn the foliage. Another option is to topdress around the plants with Sea Soil or compost, again being careful not to smother the crown. The latter will also help to retain moisture around the roots during dry spells.
Pruning – Generally speaking primulas do not require any pruning, but you can remove any yellowed foliage when dividing. Some gardeners will deadhead the spent flowers as these can sometimes sit on the crown and cause fungal problems. Falling leaves should also be cleared off the primula crowns in autumn for much the same reason.
Pest & Diseases – Botrytis or Grey Mold is the main disease problem which is generally avoided by providing good air circulation and not over-watering. Slugs and snails can be a problem but regular application of an iron-based bait should keep these to manageable levels. Vine Weevils are probably the most insidious pest problem as the grubs will feed on the roots, causing the entire plant to suddenly collapse. An application of cold-tolerant nematodes in early spring (March to early May, once soil is 5C) or again from late August to early September should keep the grubs in check.
Sun Exposure – Here in coastal BC there are many species that tolerate full sun with even soil moisture; including P. bulleyana, ‘Wanda’, P. auricula and Cowslip (P. veris). Others like Primula japonica or P. vulgaris seem to prefer open shade or partial sun exposures, with the protection of tree canopy during the heat of summer being ideal.
Soil Needs – A humus-rich medium appears to be best with well-drained soil being a necessity for such species as P. auricula. That said, many others like Giant Cowslip (P. florindae), Primula rosea and Oxlip (P. elatior) have been known to tolerate moist to boggy conditions.
All Photos Copyright to Mike Lascelle 2012-2020