I have some Primulas I would like to propagate, specifically Primula elatior and Primula veris. What is the best method, and when is the best time?
The timing will depend on the propagation method you choose. The American Horticultural Society’s Plant Propagation (edited by Alan Toogood; DK Publishing, 1999)says that division is done in early spring or after flowering; however, this method is not recommended for any species except Primula vulgaris and Polyanthus primroses. Although division is a healthy practice for some species, it can weaken others.
You can raise your primroses from seed, which has the benefit of being a virus-free propagation method. This is done in either mid-spring or in late summer to fall(the later time period is rated as easier than the earlier). However, Primula elatior, Primula veris, Primula vulgaris, and candelabra-type primroses may hybridize if you do not isolate them. Depending on your outlook, this could be a problem or an opportunity. The seeds are best sown when fresh, in a well-drained, moist soil mix rich in organic content.
There is some propagation information in this Alaska Master Gardeners article by Mary Jo Burns, entitled Growing Primula in South-Central Alaska. You may want to see if your area has a chapter of the American Primrose Society. Members of the Society have access to informative articles about all aspects of primrose cultivation.
I have grown primroses both in Seattle and in South Everett. The first time the plants looked like the leaves were being eaten, and then when I pulled one of the almost-eaten plants out of the pot, most of the roots were gone. When I cleaned out the pot, I found many little white grubs in the dirt. It happened again in my new location. I am mystified, as I grow them in pots on a second floor balcony. What could be causing this and is there a way to grow primroses without this happening?
I wonder if the problem is in the potting soil. Were you using the same batch each time? It might be worth experimenting with a new brand of potting soil to see if you have the same or different results.
Also, you could try purchasing your plants from different sources. The ones you have now may have come to you from the nursery already infested.
There are a number of pests that afflict Primula. Of the culprits listed on University of California, Davis’s Integrated Pest Management site, weevils might be a possibility, as their larvae (grubs) live in the soil. The recommended treatments include parasitic nematodes and trapping of adult weevils. Here is more on this pest, from the Connecticut Agricultural Experiment Station.
Variegated cutworms are in full force in the garden this time of year(Feb-May). Some of their favorite foods include primrose, foxglove, variegated water figwort, bearded iris, and chives. The little vandals only feed at night, so if you have suspicious holes on the leaves of your plants go out at night with a flashlight. Hand picking works, but must be done frequently. Spraying with Bt (Bacillus thuringiensis – Green Light BT Worm Killer is one name brand) works too, but plants must be re-sprayed after each rain. More information: North Dakota State University
If you’re only familiar with the common primrose sold at grocery stores in January, take another look at these charming little perennials. With over 400 species found throughout the Northern Hemisphere, there are many worthwhile choices for the Pacific Northwest garden. Try nutmeg-scented Primula florindae (Himalayan cowslip) in a wet spot or late summer flowering Primula capitata in a shaded pocket in a rockery (add compost to the planting hole). To find the one best suited for your garden conditions check out the exhaustive reference book called Primula by John Richards (Timber Press, $39.95).
The American Primrose Society website has photos of some of the less common primroses, as well as articles on growing and propagating Primulas and other Primrose family members. Members receive a quarterly journal with color photos, participate in seed exchanges and show off their prize plants at the annual meeting. To join send $25.00 to Julia Haldorson, Treasurer, P.O. Box 210913, Auke Bay, Alaska 99821.