? Alpines & Rock Gardens FAQ Page

This page provides answers to some of the frequently asked questions in the Alpines & Rock Gardens Forum.

These questions and answers were taken from previous postings to the forum and are provided here as a help to other users.

Frequently Asked Questions

 ? What defines alpine and rock garden plants?

Ruth Anne (IL. zone 5a) - What is the definition of such plants?? I assume rock garden plants would encompass those that are of the ground cover type or dwarf? What about 'alpine'? Would that be the type of plant that is grown in certain very cold zones or high altitudes?

Neil Allen ILZ5 - The "standard" definitions I've seen center on three characteristics of mountain/alpine regions: a short growing season, good drainage and relatively poor soil. larger Alpines tend to be small plants because of the short season (no time to get big) and the poor soil (no nutrients to get big, little room to put down huge roots to support a huge plant). What alpines are good for late-season display? Some small campanulas seem to go on and on, but what else? .

Barbara - Try some varieties of Sedum spectabile. The wilted flowers tend to keep their color - especially dark-red *Carmen*; late-blooming Chrysanthemum zawadskii add some Colchicum and fall-blooming crocuses.

Richard - Most alpine and rock garden plants are characterized by their tufted and dwarf nature, and by broad definition in terms of usage include plants that are not actually from areas of high altitude or cold (some sedum and sempervivums for instance). Although many are from scree conditions, others come from alpine and sub alpine meadows where the soil can be fairly rich, so I wouldn't say that soil is a defining factor at all. Also, the dwarf habit usually comes, not necessarily from a short growing season, but as an adaptive measure to reduce exposure to cold, wind, etc. For all but the purists, I would think that any plants meeting a certain criteria for plant habit could be included in a rock garden. As far as the delphiniums and lupines are concerned, although the large hybrids would look out of place, there are species within both genuses that would be quite suitable, some of which grow to only a few inches in height.

Bob in zone 6 - Neil, how about Tricyrtis? Some of the taller ones are blooming right now; is it possible that there are fall-blooming alpine species? What about dwarf Asters? I know that 'Royal Opal' blooms here in September.

Barbara Mc Z8/E-TX - Here in the south the term " rock garden" refers to cactus & succulent garden. So can alpine plants be planted in our hot, humid, sunny area?

Asle Serigstad Zone 7 - I don't think definition of alpines and rock garden plants have anything to do with soil. I also think you can divide those plants into two very different groups; 1. alpine plants growing in mountains 2. coastal plants growing in the coastal zone The first group, are plants that will benefit from being low growing, because of wind, cold, and snow cover. The second, also benefits from being low growing, mainly because of wind and the very rough climate by the sea. The first group contains plants like Dryas octopetala, many Gentiana's, Leontopodium alpinum, many Saxifraga's etc. The second contains plants like Silene maritima, most Sedum's, Armeria maritima etc. Alpines does not always like dry conditions. Most of the Saxifraga's grows in moist, some even in wet conditions. This is also the case for many Primula's. And these two genera are among the largest in alpine/rock gardening. Sedum and Sempervivums are good examples of plants that grows under very dry conditions.

George Marcus - Among late-blooming plants suitable for the rock garden are some of the fall-blooming gentians, especially Gentiana saxatilis.. Other late-blooming gentians include G. sino-ornata and its hybrids as well as related Asian gentians. Many of these put on an impressive show in September to October (e.g. G. farreri, G. veitchiorum and their hybrids) but may be rather demanding as to growing conditions, viz. peaty soil, part shade, although the hybrids tend to be more easily pleased. One of the easiest gentians, which happens also to be fall-blooming is G. sepemfida.

Heidi - I think of a rock garden as a type of garden where you work with plants around rocks, from small to boulder type, usually on a small slope or hillside, or just around rocks -- plants that can be grown between the rocks, that can cascade over the rocks. Sedum is great; Candytuft; Phlox; Thyme; Elfin Herb; Sun Rose; -- stick in some evergreen azalea; dwarf Japanese Maple; Armeria; Coreopsis; Diascia (Blackthorn Apricot!); Spruge; Burning bush. I think of Alpines as Edelweiss, Arctic Iris, Norwegian Pine - all that can survive having snow occasionally.

Kathy PA/Z6 - In my rock garden I have a Yucca, geum, sea holly, thistle, hens and chicks, poppies, thyme, cactus, moss rose.

Neil Allen ILZ5 - It also helps to think of some alpines as plants that would colonize the poor, gravelly soil you'd find next to a retreating glacier. As more organic matter was added to that soil (blown by the wind, for example), a greater variety of plants could grow there and the "alpines" would retreat with the glacier -- up the sides of mountains, for example. Some areas would always remain very tough environments, though -- for example, cliffs along the edge of the sea, and there you would also find rock plants that shared a lot of characteristics with "mountainous" alpines. Also, at high latitudes you're likely to find the same short summers, cold but non-rainy winters and relatively poor soil that you find at high elevations, so here too you'd find plants that have made their way into rock gardens even though they don't originate at especially high elevations. So while an alpine is, strictly speaking, a mountain plant, an "encyclopedia of alpines" might include those cliff-dwellers and high-latitude plants -- or it might not. "Rock garden plants" is in some ways a more inclusive phrase because it can take in all three types, but it also usually means that the plants should be less than a foot or perhaps two feet tall.

 ? Any suggestions for easy to maintain rock gardens?

Sue Benoit/North.Ontario/Z4 - Do you have any suggestions for rock gardens that are easy to maintain?

Bill Dabroski - You could make your garden all mountain phlox (i.e. mountain pink) including the various colors. I find that sedum with their vigorous growth tend to out compete most weeds. Plus, the sedum usually reseed as well as division being a rapid propagation method to cover a larger space.

Asle Serigstad Zone 7 - I grow lots of Sedum, Sempervivum, Armeria, Silene, Thymus, Phlox, etc.... If you plant these kinds of alpines, that grow well under dry conditions, the weed will have to grow very fast. I mix the soil with lots of gravel, and this keeps the soil dry. In addition I have a layer of gravel, 3-5 cm on top, to prevent weeds and to avoid rotting of plants. It is important to make different zones in your garden, with adapted conditions for different plants. If they have good conditions, they will be better competitors to the weeds.

 ? What are some alpine & rock garden plants that bloom in the summer?

Majella Larochelle - First, out of more than 8000 kinds of these plants, I would assess than 10% of them blooms in summer: that makes a choice of 800 kinds of plants, plus the more than 2000 kinds of Sempervivums usually starting to bloom in July. Starting in April, here are some ever bloomers: - from April till November: Viola corsica, Scabiosa japonica alpina, Scabiosa columbaria 'Nana', Linanthastrum nuttalii (summer Phlox) and from the end of July, almost every genus has a least a species or a cultivar that will bloom by mid-summer. Aquilegia 'Nicole', August-Oct., Penstemons in quantities, Alchemillas, perennial Cyclamen some alpine Digitalis, Geranium.. Lysimachia japonica 'Minutissima' is a jewel with plenty of yellow stars from July to October. Many Gentians, one is called Fall Gentian: G. septemfida Miniatures Hosta and Astilbes.

Neil Allen ILZ5 - Sea Thrifts -- Armeria juniperifolia and maritima "Splendens."

Sue - North. Ontario, Z4 - In my rock garden my favorite is Coreopsis 'Moonbeam'. It's constantly in bloom till frost. It likes a well-drained soil in a sunny location.

Gail Korn NE Z4B - Erodium reichardii 'Charm' never got more than 1.5" tall and bore little pink flowers veined rose all season long. It reminded me of a miniature cranesbill. Also I would recommend Scabiosa 'Butterfly Blue' and Scabiosa 'Pink Mist'. The latter is a pinkish lavender. Both scabiosa are about 1' tall and wide and bloom June till frost. They do bloom well all summer but they pick up steam and look their bloomiest best in the fall. They are also frost-cheaters.

Bill Dabroski - I have a type of Anemone sp., probably sylvestris 'Snowdrop Wildflower' in the rock garden that blooms regularly but sparingly in the fall, having its major bloom in the spring.

Asle Serigstad Zone 7 - Geranium sanguineum blooms from June to October. Mimulus luteus/cupreus cultivars, different Dianthus sp./cult., etc.

 ? What is a trough?

Robin - 9/CA - A number of you are talking about troughs, and I am not sure, gardening-wise, what that is.

Judi z. (RI/Z6) - Troughs are a type of container, usually not very deep, and rectangular--almost like a sink. I admit to being an anglophilic gardener, and troughs are very popular there--the thing I like is that you can make a miniature landscape with them.

Donna - 5 - A trough, like a an old drinking trough for a farm animal, is usually rectangular and often lower to the ground than the typical drinking trough and often made of stone or hypertufta.

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