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
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
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.