Plants For A Rock Garden

So many plants are suitable for a rock garden that the range of choice

is bewildering. In this, as in the laying out of the garden,

advisability takes precedence over pure personal desire, though, very

fortunately, it is often not difficult to make the two go hand in hand;

a little intelligent thought helps a lot.



To the beginner, no better advice can be given than that which applies

to the picking out of the rocks--use the material which is close at

hand. This is not, by any means, a mere suggestion to follow the lines

of least resistance. It is far more. In the first place, there is always

an endless amount of beautiful and suitable plant life to be had

without going far afield. Then again, natural harmonious effects in your

immediate neighborhood are pretty sure to be appropriate to your

grounds. Finally, you can see for yourself how things grow, and as for

the hardiness of plants, you have it already tested for you. This refers

not alone to the natural conditions; there is a second wide field in the

gardens--the hardy gardens--of others, where you can at once choose from

the many and learn whether certain plants are too tender or require too

much care for your use.



So far as plants native to the immediate neighborhood are concerned,

their value to the rock garden of the average person with limited time,

who is not obsessed with the idea of growing the rare and curious,

cannot be overestimated. And they are so many; more than most realize,

and often of an individual beauty not always appreciated in the

bewildering profusion of the wild but plainly apparent when an

individual, or a little group, is open to close study in a rock garden.

Do not make the rather common mistake of thinking that they are too

familiar to be interesting; they are never likely to be. And, honestly,

can you say in your heart that they are?



For a Connecticut rock garden the Greek valerian (_Polemonium reptans_)

must be purchased, unless a neighbor can spare some from his collection

of old-fashioned flowers; there it belongs in that category. But why

should you of Minnesota or Missouri deny so beautiful a flower a place

in your rock garden, simply because you have only to go to the woods for

it? The English enthusiast brings home primroses from the Himalayas,

gentians from the Swiss Alps, and _Dryas Drummondi_ from the Canadian

Rockies for his rock garden, but he does not fail to take advantage of

some of the common things near-by--even the "pale primrose" and the

cowslip.





From ferns alone, or from only plants of shrubby growth, a most

beautiful native rock garden may be made. And adding small flowering

plants, or excluding all else, there are limitless opportunities. It

goes without saying that A's rock garden in Maine will not be like B's

in Louisiana; but there is no law compelling it to be.



Among the common wild flowers of the East that take on unexpected new

beauty when transferred to the rock garden are the celandine

(_Chelidonium majus_), strawberry (_Fragaria Virginica_), cranesbill

(_Geranium maculatum_), toadflax (_Linaria vulgaris_), orange hawkweed

(_Hieracium auranticum_), herb Robert (_Geranium Robertianum_),

coltsfoot (_Tussilago Farfara_), Solomon's seal (_Polygonatum

biflorum_), foam flower (_Tiarella cordifolia_), bloodroot (_Sanguinaria

Canadensis_), and some of the violets. These are but a few names, and

random ones at that. Some of them, the coltsfoot, cranesbill, celandine,

and toadflax, spread too rapidly, but by careful watching and not

allowing the seed to ripen, they may be kept within bounds. There are

many such plants that will take all the room in sight if they are

allowed to, and they must be watched closely, or else discarded

altogether. Some of them answer a good purpose by giving the rock garden

a quick start, after which they may easily be reduced or thrown out

altogether. There need be no compunction about discarding. Certain

plants, like certain friends, you enjoy having for a visit, but do not

care to see remain forever and a day.



Annuals as a class are not desirable for the rock garden; for one thing,

the care of renewal is too great. Biennials are almost as much care, but

in each case there will always be exceptions that are a matter of

individual preference. Few, for example, would have the heart to reject

the dainty little purple toadflax of Switzerland (_Linaria alpina_),

just because it is a biennial. The main dependence, however, must be

placed on perennials--the plants that, barring accidents, last

indefinitely. These should be mostly species; if horticultural, do not

use the bizarre--Darwin tulips, for example, or the Madame Chereau iris.

Nor, with rare exceptions, should double flowers be used. A double

daffodil looks horribly out of place, while the double white rock cress

(_Arabis albida_) will pass.



The easy rock garden plants, where the material is not taken from the

wild, are to be found in most of the large hardy gardens of the East.

Some of them are natives of Europe or Asia, and more than is commonly

suspected are at home in other parts of the United States. Among the

best of these for carpets of bloom are _Phlox subulata_, _Phlox

am[oe]na_, _Aubrietia deltoidea_, maiden pink (_Dianthus deltoides_),

blue bugle (_Ajuga Genevensis_), white bugle (_Ajuga reptans_), woolly

chickweed (_Cerastium tomentosum_), creeping thyme (_Thymus serpyllum_),

dwarf speedwell (_Veronica repens_), _Saponaria ocymoides_, alpine mint

(_Calamintha alpina_), and pink, white, and yellow stonecrops (sedum).

All of them fairly hug the ground. There are other plants that form a

carpet of foliage, but the flower stalks rise higher. These include

white rock cress (_Arabis albida_), the permissible double buttercup

(_Ranunculus acris fl. pl._), the also permissible double German

catchfly (_Lychnis viscaria_), another double flower, "fair maids of

France" (_Ranunculus aconitifolius_), Carpathian bellflower (_Campanula

Carpatica_), grass pink (_Dianthus plumarius_), _Iris pumila_, crested

iris (_Iris cristata_), Christmas rose (_Helleborus niger_), _Phlox

divaricata_, _Phlox ovata_, _Phlox repens_, foam flower (_Tiarella

cordifolia_), _Veronica incana_, _Alyssum saxatile_, _Saxifraga

cordifolia_, and various avens (geum).



Several of the primulas give a like effect if the planting is close--as

it should be in a pocket. The best are the English primrose (_Primula

vulgaris_), cowslip (_P. veris_), oxlip (_P. elatior_), bird's eye (_P.

farinosa_), yellow auricula (_P. auricula_), _P. denticulata_, and _P.

Cortusoides_. Similarly, spring bulbs may be employed; plant them, for

the most part, under a ground cover so that the soil will not show when

they die down. Of the tulips, single ones of the early and cottage types

may be used, if in a solid color, but most to be preferred are the

species, such as the sweet yellow (Florentine) tulip of Southern Europe

and the little lady tulip (_Tulipa Clusiana_). Crocuses are also best in

type forms, and the small, single, yellow trumpet kinds are the finest

daffodil material. Single white or blue hyacinths may be used, but

better than the stiff spikes of bloom of new bulbs will be the looser

clusters of bulbs that have begun to "run out" in the border. Other

valuable bulbs are the snowdrop, _Scilla Sibirica_, glory-of-the-snow

(_Chionodoxa Luciliae_), guinea-hen flower (_Fritillaria Meleagris_),

grape hyacinth (_Muscari botryoides_), _Triteleia uniflora_, _Allium

Moly_, and the wood and Spanish hyacinths (_Scilla nutans_ and

_campanulata_).



Taller plants that may be worked in, oftentimes best with only a single

specimen or small clump, are autumn aconite (_Aconitum autumnale_),

_Yucca filamentosa_, leopard's bane (doronicum), single peonies (either

herbaceous or tree), German, Japanese, and Siberian iris, as well as the

yellow flag (_Iris pseudacorus_), single columbines, _Anemone Japonica_,

_Hemerocallis flava_, _Sedum spectabile_, _Dielytra spectabile_,

_Dielytra formosa_, Jacob's ladder (_Polemonium Richardsonii_),

fraxinella, _Anthemis tinctoria_, single _Campanula persicifolia_,

_Campanula rapunculoides_, _Campanula glomerata_, globe flower

(trollius), snapdragon (antirrhinum), platycodon, lavender (where it is

proven hardy), and musk mallow (_Malva moschata_).



Of the lilies, _Lilium Philadelphicum_, _L. elegans_, _L. speciosum_,

and _L. longiflorum_ are all desirable, and they thrive in partial

shade, though in Japan _L. elegans_ will be found standing out from the

rocks in full sunshine. For peering over into the rock garden, rather

than being placed in it, _L. Canadense_, _L. tigrinum_, and _L.

superbum_ are recommended.



The pick of the low shrubs are the charming _Daphne cneorum_, which

flourishes better for being lifted above the ordinary garden level, and

_Azalea am[oe]na_. The latter, however, should be so placed that its

trying solferino does not make a bad color clash. Rhododendrons and

mountain laurel fringe a rock garden well, and with one trailing

juniper (_Juniperus procumbens_) will provide a great deal of the

refreshing winter green.



Single roses, the species, fit in well where there is room for them.

Good ones are _R. setigera_, _R. rubiginosa_, _R. Wichuraiana_, all

rampant, and the low _R. blanda_. The roses would better be at or near

the entrance or exit, or far enough above the rock work not to ramble

over small plants.



The plants in this list cover all seasons and vary somewhat in their

soil and moisture requirements. But the variation is nothing beyond the

ordinary garden knowledge. Most will do better if their preferences are

considered, but none is apt to perish with average care.



Alpines, as a class, would better be left to the amateur with the time,

money, and disposition to specialize. Most of them take kindly to being

transferred from a mile or more up in the air to sea level; the

edelweiss, for one, grows here readily from seed, and the exquisitely

beautiful _Gentiana acaulis_ thrives in American rock gardens. But, on

the whole, alpines do not do as well here as in England, where the

summer climate is not so hard on them. When they flourish here, it is at

the cost of a great amount of professional care.