Tips On Growing Primula
By Herb Dickson, Chehalis Rare Plant Nursery
Starting with seed:
Most primula like cool, moist spring weather with a temperature range between 40 and 60 degrees F to germinate. Freezing the seed is not necessary, but will not hurt the seed or the young seedlings. Here is my successful method developed from many years of trial and error.
I plant during January, February and March here in the Pacific Northwest. I use 4″ deep, 4″ square plastic pots. The deep pots serve as a reservior for water and give me a psychological factor that I will tackle a 4-inch pot at transplanting time, but hesitate to start a whole flat of seedlings. I use a sterile seeding mix (there are several brands on the market and all are good), fill the pots 3/4 full, then add a slow release fertilizer containing trace elements about one level teaspoon per pot and stir it abit. I finish filling the pot to the brim, press the soil down and level it 1/4 to 1/2 inch below the top. Scatter the seed on the surface as even as possible, cover with a layer of vermiculite and place a cotton cloth cut to fit on top inside the rim. Place a few pieces of coarse grit or pea gravel on the cloth to keep it from blowing off when dry. Give an initial light watering from on top with a fungicide (follow label instructions for strength).
Put the pots in flats and set the flats outside on benches fully exposed to sun, wind, rain and snow until the seed germinate. Remember, never let the seed get dry. The cloth cover helps keep in moisture and makes watering easy from overhead, keeps the rain from washing the seed out, and keeps the birds from eating the seed. The layer of vermiculite keeps you from taking in the seedlings with you when you remove the cloth. When the cloth is removed place the pots in well-ventilated shade.
There are two times when transplanting is usually successful. The first occurs when two to four true leaves have developed. The second is much later after some heavy tactile roots have developed. Some of the small and slow growing species are too small to handle during the first time. You will get better results leaving them undisturbed in the seed pot over the first winter and transplanting the next spring as they start to grow.
Some of the new systemic fungicides work wonder on primulas that are very difficult to keep alive in hot summers. It is not the heat primarily but a root rot fungus that grows in warm, moist soil.
There are three times each year to divide crowded primula plants in the Vernales and Auricula sections: 1) when they first start new growth in the spring; 2) right after flowering; and 3) in the early fall (late August or early September). They need three to four weeks of growing weather before it gets hot in the summer or freezes in the winter. To divide candelabras and others that go dormant, the early spring as growth starts is the only reliable time to divide. Do not divide after flowering.
The genus Primula contains a diverse group of species, some tropical, some polar, some lowland, some alpine, some desert, some swamp. As you progress you may want to try some of the difficult species. Many have yet to be established in cultivation.
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