by John Richmond(john.richmond(at)virgin.net)
There are some hardy perennial plants that we, as gardeners, simply must have. This is despite the fact that, as a rule, we seem unable to keep them for any length of time. In my own case these are plants such as the red shingled, lilac flowered Primula vialli; Meconopsis betonicifolia, the Himalayan Blue Poppy; delicate sky blue Corydalis flexuosa; antique violas such as gold and purple 'Ardross Gem' or yellow and brown 'Jackanapes'; or the yellow flowered Iris danfordii.
These plants are sometimes described as the nurseryman's friend. Relatively easy to grow in quantity, irresistible at the garden centre, more likely than not to die out in our gardens, but so beautiful we always come back in a year or so to renew supplies.
I know I do. I've had and lost all of these, some a number of times. And that can prove expensive. But there are ways we can keep them going a little longer. Mostly it is a question of understanding their needs and being prepared to put in that bit of extra effort.
Take Primula viallii. In flower in May or June this is irresistible at the nursery or garden center. We buy one, even two plants and put them in a moist, lightly shaded spot. We protect them from slugs and cut off the flowered stems to prevent exhaustion after flowering. Come autumn they develop small resting rosettes that may last most of the winter. But nothing comes up next year.
It's not really surprising. These plants are frequently monocarpic, their rosettes usually dying after flowering. In exceptional circumstances they can produce daughter rosettes which will carry on for a year or two longer but the chances are good they will die out in your garden.
The trick to growing them is to buy not one or two but five or more. This vastly increases the chances that viable seed will be set. Gather this in late summer, sow on moist compost in a cold frame and you will soon get a thicket of seedlings ready to grow on to be planted out the following year.
The shade and acid-loving Himalayan blue poppies are similar. Equally prone to die after flowering they often disappoint by not re-emerging the next spring. But even solitary plants set seed in profusion. As soon as I realised what I was doing wrong I collected seed from a single plant when it matured in late summer. Within two months I had enough seedlings to fill the eighty cells of two plastic trays. Most came through the winter in a cool greenhouse, grew on in pots in a shaded frame for the following year and flowered the year after in their permanent positions. The effect was magical.
Corydalis flexuosa is a different story. I have never been able to keep it in the open ground despite digging in garden compost, leafmould and other organic material to generate the woodsy soil they need. The reason is slugs. Most perennials are not that attractive to slugs when they disappear underground. It seems that Corydalis flexuosa is. It disappears by mid summer and by fall the small slugs that thrive in my organic garden will have finished it off. No wonder it doesn't re-appear the next spring.
I now grow the corydalis in a large pot where it underplants Hostas 'Honeybells' and 'Wide Brim', Cordyline 'Coffee Cream' and a variegated Vinca. Light shade suits them all and the Corydalis appears to be thriving in its mixture of soil-based and ordinary potting compost. It has now reappeared for the second year and looks set to continue for years to come.
The beautiful named varieties of viola (I grow about a dozen of the 400 or more named varieties) are also naturally short lived. Because they are cheap the tendency is to accept their loss and simply replace them. But they can readily be kept going by cuttings taken in late summer and over-wintered in a cold frame. These are pretty hardy plants. They don't need much cosseting. By spring they will have produced bushy plants ready to carry on throughout the summer.
However, I admit that Iris danfordii has defeated me. Essential for its yellow flowers in mid winter the bulbs split up into tiny bulbils after flowering. Growing them on to flowering size takes both years and the right soil. I buy afresh when I feel the need using the money I've saved by keeping my other treasures going.
Still, four out of five isn't a bad success rate. If you're prepared to put in some extra effort meeting the special requirements needed to keep these plants going in your garden you'll have preserved some treasures - and saved yourself some expense.
About the Author John Richmond is a keen gardener who lives and works in the South West of England. He has a scientific background as a professional ecologist. He has written occasional articles for gardening and other magazines in Britain since 1984, specializing in garden wildlife issues and hardy plants.