Plant of the Season - Spring

Primula allionii

As the great alpine plant author, Reginald Farrer wrote, “this is the jewel of jewels among our European saxatile species”. Yet, I feel that there is little value in extolling the virtue of a stunning plant purely for its natural beauty when it gives the keen gardener little or no chance of cultivation. We are under no illusions as to its virtue as a pan-grown plant under glass or its successful culture in a protected “tufa” cliff. So what about its culture, aside from the two afore-mentioned suggestions? In an open garden situation, provided plants are given winter protection from overhead precipitation, plants can be brought to successful flowering.

Let’s consider for a moment from where this species is native and just why Primula allionii is so special. The plant is only native to a restricted location in the Maritime Alps between Cuneo and Nice, predominantly in France. It grows as a saxatile (i.e. living amongst rocks) plant preferring a vertical position in a type of limestone that is easily identified from its colouration and is often referred to as Breccia conglomerate, somewhat akin to our own “tufa” rock. Perhaps significantly, despite its precarious position careful inspection reveals that the cliffs are pitted and allow falling rain to drain through the plant’s roots as opposed to running off and causing the plants to dehydrate.

The primula is more generally found growing in south-facing exposures, but can just as easily be located in shaded caves. I have photographed it in full flower between the 12th and 15th March at an altitude of 700m. It is hard not to become overly ecstatic on finding the plant in its native habitat at its floral best. The temptation to collect wild plant material should be strongly discouraged as there is such an abundance of cultivars of this stunning primula available in the alpine trade and all those privileged to travel to these parts should be allowed to enjoy the full range of plants in all its glory.

I hope that having created a picture of how this primula performs in nature we can now translate some of its essential requirements to the garden setting! The most successful method of growing it is in blocks of “tufa” rock. Tufa is a relatively lightweight, extremely porous, calcareous rock and holes can be bored into its surface with relative ease. The name tufa comes from the latin tofus, meaning a soft stone. I would recommend that, having purchased some pieces of tufa (at least 60cm sq) they should be positioned in an open, but sheltered location and buried up to a quarter of its depth so as to allow some moisture uptake by capillary action. I would carry out the planting in early spring to give the plants a full season to get established. First of all drill the holes at 45% to the vertical in order to retain the plant and compost. The holes should be about 25-30mm in diameter and up to 9cm deep. Young plants should be chosen with a small rootball no larger than a walnut. Have an empty tray available to retain materials for planting. Loosen the soil carefully from the plant and retain the substrate and mix this with the tufa residue that has been created from the hole and mix with a little extra sand. Prior to planting it is important to thoroughly soak the piece of tufa and allow it to drain. The small plants should also have been well watered prior to planting. Having loosened the soil from the plant we are ready to insert the root system. It may be helpful to lay the roots on the back of a pointed, concave tool to ease the roots into the hole. Before back-filling make sure that the neck of the plant is in the correct position. Carefully add the compost, a teaspoon at a time and firm gently with an appropriate tool. It is important to carry out this operation carefully to ensure there are no air pockets or damage to the roots. Water carefully and maintain a regime of watering until the young plants are established. I would strongly recommend positioning this block of tufa so that it can be effectively covered or protected with a pane of glass/polycarbonate during the dormant season. I would experiment with Primula allionii in a variety of positions to see which works best of all. In the shadier positions, try a few plants of Kabschia saxifrage or a Jankaea – sadly we are now supposed to spell the generic name Jancaea due to an original mistake made by botanist Boissier in 1875! There can be no doubt that this form of gardening with the specialist use of materials like tufa will allow the successful cultivation of some of the worl’s most challenging and enchanting alpine plants.