NOTES ON A ROCK GARDEN. 



425 



Nierembergia rivularis, from Argentina, is a pretty little creeping 

 plant producing large, white, cup-shaped flowers. It succeeds best in 

 good strong loam, peat, and leaf-mould, in rather a moist position, with 

 full south exposure ; it should be top-dressed in the autumn ; increase 

 by division. 



Zauschneria calif ornica and its var. mexicana are bushy little plants 

 from California and Mexico, bearing vivid scarlet tubular flowers in 

 late summer and autumn. They should be planted in a gritty compost 

 containing limestone or mortar rubble, on a hot sunny bank ; top- 

 dress in late autumn or early spring. Z. c. mexicana flowers more 

 freely than Z. californica. 



Gentiana acaulis is perhaps the best known of its genus and 

 one of the loveliest of alpine plants. It likes a deep gritty 

 loam with limestone in it, in not too dry a position, but in full 

 sun. It is glorious for massing on the rock garden, forming rosettes 

 of sturdy green foliage, bearing great bell-shaped flowers on short 

 stalks of a blue, the intenseness of which has become proverbial. 

 There are gardens in which it is difficult to induce this lovely plant to 

 flourish, but they are rather the exception than the rule ; increase 

 by division or seed. G. verna is a wonderful little alpine, growing an 

 inch or two high and bearing white-throated star flowers of gorgeous 

 sapphire-blue. It requires special treatment to flower it well. It 

 does exceedingly well at Wisley, planted firmly in a flat position low 

 down on the rock garden in a good, moist, loamy soil, grit, and lime- 

 stone, protected from midday sun. It should be top-dressed once or 

 twice a year. 



Primula is a beautiful genus, and many of the species are quite easy to 

 grow in the half-shady moist nooks of the rock garden in a deep loamy 

 compost and a little leaf -mould. P. frondosa is quite happy, tucked 

 away in a little damp corner, where it will flower freely. It does best 

 by being raised from seed annually. P. japonica, P. Bulleyana, and P. 

 denticulata are all easy to grow where there is moisture. P. rosea, when 

 planted at the water-side, where its roots can get plenty of moisture 

 during the growing season, soon flourishes and looks quite at home. 



Only a comparatively few of the rarer and more interesting plants 

 have been dealt with, as the common ones are so well known, such as 

 Aubrietia, Sempervivum, Arabis, Alyssum, Achillea, Viola, Anemone, 

 Arenaria, Cyclamen, Erinus, Gypsophila, Iberis, Linaria, Oenothera, 

 Alpine Phlox, Potentilla, Saponaria, Silene, Thymus, Tiarella, Armeria, 

 and many others, including a few of the many small bulbs, such as 

 Iris, Scilla, Chionodoxa, Narcissus, Hyacinthus, all of which help to 

 make a glorious show of flowers during the spring, and most of them 

 are of easy cultivation and will grow in any ordinary garden soil. 



It should be mentioned that it is most important, when planting, 

 to put all roots down deep and plant firmly. 



VOL. XLI. 



2 F 



