The lush Polyanthus primroses from West Coast breeders had been so impressive in the garden that two years ago, I decided to try them in my greenhouse for late winter bloom.
My choice was the blue shades—huge blossoms toned a rich blue, stitched with gold around the edges and gold in the center too.
Starting Polyanthus Primroses Seeds
I ordered a full packet of seed for five dollars at the end of June to get the new-crop seed. The packet was kept in our home refrigerator until the end of July.
Sowing earlier than this would require extra care of tender seedlings during the summer heat.
I used six-inch clay pans for starting seeds. They had a crock in the bottom for drainage, then soil and leaf mold screenings for the lower two inches.
The soil mixture itself was of equal parts loam, sand, leaf mold, and peat moss, run through a one-quarter-inch mesh screen. This filled the pans to within a half-inch of the top.
The seed was scattered thinly on the soil surface and pressed in lightly but not covered. After sowing, the pans were watered by placing them in water until moisture showed on the soil’s surface.
During Early Stage Of Primrose
All during the early life of my primroses, they were kept in a shady part of the greenhouse where a double thickness of saran green shading cloth was stretched overhead. In addition, the pans were covered with a sheet of glass until the seed germinated.
To maintain constant moisture, each pan stood in a low saucer of water. One must keep an eye on the pans because too much moisture can cause seedlings to rot as they come up. Lift the glass at night for ventilation when too much moisture collects.
Germination
Germination began in ten days to two weeks. A few seeds delayed germination for several weeks.
By early October, when the young plants had their second pairs of leaves and strong roots, I found I had 250 to 300 plants from the one packet of seed.
Transplanting Seeds
Standard 4-inch-deep wooden flats were prepared for transplanting. I have found deep flats easier to keep watered, and plants develop heavy root systems in them.
Bone meal, old manure, and oak leaf mold were added to the soil mixture used for the seedling. Plants were spaced out 2” inches in the center.
Some shade was kept over the transplanted seedlings until they were rooted in. After that, they were given full sun all winter long.
Final Transplanting
By late November, the flatted seedlings were ready for a final transplanting to 4-inch pots. The potting mixture used a little loam to give it more body and some extra bone meal.
Care was used to set the young plants with the crown or base of the leaf stems at the soil level. Too deep potting can cause rot. The soil was formed with the thumb in potting but not pressed so hard as to crush the tender roots.
Keep In A Cool House
The beauty of growing these promises is that they can be kept in a cool house. Night temperatures averaged 45° degrees Fahrenheit, and with ventilation, on sunny days, temperatures were 50° to 55° degrees Fahrenheit.
Even in the dead of winter, my plants kept growing steadily at these temperatures.
First Flowers In Early February
By early February, the first flowers opened. Strong heavy stems bore clusters of flowers in which individual blossoms were as much as two and one-half inches in diameter.
In most cases, each plant bore three stalks, one after another, giving three months of continual bloom.
Since the flowers had the protection of the greenhouse and steady cool temperatures, the quality and color of bloom surpassed anything I had grown outdoors.
Indoor Flowering In April
The end of indoor flowering in late April was not the finish of the plants. They were then set out in the garden in a suitable location.
Mine got some shade, and the bed faced east to get morning sun only. Primroses cannot stand the heat.
The soil is full of humus, and soil moisture is adequate. Under these conditions, some old plants gave a few additional blooms that spring, more in the fall, and by the following year, were fine heavy clumps.
Another Way To Start Primrose
There is still another way to start these blue primroses, but in this case, the object is to have a batch of young plants ready for planting in the garden by spring.
Seed, in this instance, is sown at the end of October.
The plants bloom by April and, when set directly into the garden from flats, will bloom steadily until early June.
Finest Plants From Seed Production
The finest plants, in any case, may be selected for seed production. Blossoms must be pollinated by hand, and even then, the quantity of seed produced is small.
Only part of the seedlings will be like their parents; the rest will be off-type. Purchased seed is by far the best, especially when an outstanding winter show is desired.
Never have I grown any hardy plant that gave such a great return in such a short time from seed. A bench of blue primrose next to golden daffodils turned our greenhouse into a bright spring garden.
Image/s: (Page 32)
Primrose plants set close together on the greenhouse bench make a carpet of blue as in the garden. Blossoms average over 2 inches across. Golden daffodils are grouped beyond.
44659 by Harold Epstein