Growing Primulas From Seed

Primulas are the real aristocrats of all the spring flowers that gladden the eye, or so it seems to me. This is by no means a suggestion that daffodils, tulips, scillas and other spring flowers are not lovely.

Many gardeners have one or two primulas in a rock garden where they are quite at home, but there is no more lovely sight than a whole border or bed of primulas on the north side of a row of deciduous shrubs dappled with the early May sunlight.

The fact that primulas are grown in relatively few gardens is probably due to a false reputation of being “difficult.”

Some species are difficult and almost impossible to grow and flower in the New York City climate.

There are many species such as Primula polyantha, Primula denticulata, Primula acaulis, Primula japonica and Primula Sieboldi, to name but a few, which are easy to grow from seed and to maintain in the garden if one follows simple rules and gives them the conditions and culture they like.

They will live in the garden for years if given well-drained humusy soil, semi-shade, water during hot, dry spells in summer, and winter protection.

Red primula blooming in the landscape

For the Newbie

For the beginner I would recommend Primula polyantha as one of the easiest to propagate and one of the most beautiful of all primroses.

It is a modest plant with obovate leaves 4 to 6 inches long, with flowers borne in an umbel on a 6- or 8-inch scape.

Flower color is in shades and combinations of white, gold, yellow, tawny and red mahogany, usually with an “eye” of one color and the margin of the petals another. A great deal of hybridizing has resulted in some really spectacular flowers both as to color and size.

While it is often easy to buy primulas from a local nursery or from specialists, it seems to me that, it is much more satisfactory when one grows them from seed.

One can buy enough seed to produce dozens of plants for the price of one or two seedling plants. The satisfaction of actually growing the plants cannot be bought – it is one of the joys of gardening which gives a real feeling of accomplishment to the gardener.

Primula seeds do not germinate as readily and rapidly as do zinnia seeds, and this may be one of the reasons why some people think them difficult.

They do germinate readily if handled properly even though it may take from three weeks to several months depending on when they are planted.

I have found that the easiest and surest way to realize good germination is the old-fashioned method of planting in the fall and leaving the seed flat at the north side of a wall until spring.

Primulas in nature are accustomed to cold winters and a heavy snow covering, so pack them with snow when you can.

Seedling Soil Mix

The soil mixture for seeding should be loose and not heavy. I find that a mixture of one part each of loam, leaf-mold and sand works well. This should be passed through a 1/4 -inch screen and the coarse screenings placed at the bottom of the flat for drainage.

Primula seed is fine and should be pressed into the soil and covered, if at all, with only a dusting of sand or finely screened sphagnum moss.

It is well to cover the seed flat with a screen to keep out rodents, and over the screen to place a piece of coarse burlap to prevent the heavy rains from washing the seed about.

When spring comes the flat should be examined from time to time and the burlap removed when the tiny green leaves begin to show. Keep it in a shaded location and water with a fine spray when necessary.

Transplanting Time

When the plants are large enough to transplant (and this is a matter of personal taste and manual dexterity, usually when the third leaf appears and the first leaves are about one half inch in diameter), they should be pricked out carefully.

The roots of these small plants are surprisingly long and bushy, and care must be taken to avoid tearing them. At this point do not discard the seed flat, as additional plants may keep coming for some weeks and there is a general feeling that the stragglers often make the best plants.

The seedlings are 1 spaced 2 inches apart in a flat filled to the top with soil. The soil mixture I use consists of two parts of good garden loam, one part of sand and leafmold plus a 6-inch pot of granulated peatmoss per flat – however a good bagged soil mix will work just fine.

It is a good idea to sterilize the soil before transplanting seedlings (as well as before sowing seed) simply by pouring a kettle of boiling water over the flat and letting it stand for about three days, by which time the soil is moist but not too wet for planting.

In planting I use a half-inch-diameter dibble, but a pencil will do as well. After the roots are coaxed into the hole, firm the soil about them by pressing the dibble into the soil near the plant. This firming prevents air pockets which might result in eventual death of the plant.

Spread some slug bait around your seedlings as it is a frustrating and unpleasant experience to find a flourishing batch of seedlings reduced to a few midribs of leaves. Slugs and snails apparently find primula leaves simply delicious.

There is no reason to think that one can sow primula seed only in fall. Sowing any time through March will give the same results. If the seed is kept for any length of time before planting, it should be stored dry in a refrigerator.

Fresh seed of most perennials germinates more rapidly than old seed, and this is true of primulas. However, if you must sow in summer keep your seed flat in as cool a place as you can find, as primulas like cool conditions for germination.

Artificial freezing of the seed will hasten germination if it is desirable to plant in the summer when natural freezing conditions do not exist outdoors. The seed is moistened in the packet with a drop or two of water and placed in a deep freeze for a few days, then thawed for twenty-four hours, refrozen for one or two days, rethawed for twenty-four hours and planted.

The first moistening after planting is done with water at 110 – 120 degrees and the second watering two days later at the same temperature. The seed pan should be covered with glass and paper, and watered from below from then on.

Slow-germinating seed such as primula seems to do best if the pans or flats are kept in a closed propagating case in the shade. My case is 3 x 2 feet, 12 inches high at the back and 8 inches in front, with a hinged lid made of a wooden frame with a translucent plastic cover.

The case is filled to a depth of 6 inches with sand or a mixture of sand and peat which is kept damp at all times. The pots or flats are sunk into the mixture, and the case is kept closed except for inspection and watering.
Partial shade should be given to seedlings which have been pricked out into flats. Keep seedlings moist but never water late in the day as that invites damping-off.

They should be large enough to transplant to their permanent location in a shady border or rock garden by late September.

Winter protection should be provided. Evergreen boughs are preferable, although hay may be used provided it is not allowed to pack down.

Diseases and pests are seldom troublesome. Sufficient water must be provided during dry, hot spells in summer.

There is no dobut that after you have grown a batch of primulas from seed and been introduced to this wonderful primula family you will not be content until you have grown Primula auricula, the ultimate in primula culture.


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