There are many areas of New England where people garden in places where there are many trees. Where the trees are tall, even large, open gardens may well be in shade for part of every day. So this list is being constructed with the assumption that many people will have rock gardens containing shade-tolerant or even shade-loving plants. In cases like this, the plants are often somewhat larger than what one would grow in a full sun rock garden.
Many of the shady plants are spring ephemerals, which disappear completely in May and June, so it is wise to intersperse them with plants that come up later and expand to take the place of those that have died down. They often have seeds that are also ephemeral, and so need to be planted as soon as possible after the seeds are ripe, but in many cases you can get these plants as bulbs, corms, or tubers rather than growing them from seed.
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Persian rock cress flowers from late May into June. It has heads of small, light pink flowers on the tips of 8” stems clothed in linear gray-green leaves. The plants are about 12” wide. They are fairly short-lived, but they self sow without becoming weedy.
Curly chives flower in September to October . The flowers are delicate pale lavender pom-poms on stalks about 4” tall. The main feature of this plant is the ‘nest’ of swirling glaucous leaves, which are about 1/8” wide and 4” long. Each leaf is twisted as well as curled, giving rise to the highly appropriate name, ‘Blue Eddy’, bestowed on a very good selection made by Mark McDonough.
This native of Japan and Korea blooms into October and November when practically nothing but mums are blooming. So if a late spot of red-violet is called for, it fills the bill. In addition to the species there are two varieties – a pure white flowered form which is bright, and a larger red-violet form called ‘Ozawa’. The white flowered form grew for us for many years until it was selectively eaten by voles who picked it out from among several magenta ones. It seems it lacked a repelling factor as well as color.
This is mildly aggressive plant. Its flowers can be white as well as several shades of blue-violet. The flowers are usually round with a single row of petals surrounding the center. There is a lot of variation in the shape of the petals from narrow to wide. A named variety called ‘Vestal’ has a dense powder puff of white in its center. There is also a plant called ‘Green Feathers’ that has mixed green and white flounces where petals should be. It’s actually very attractive. Some of the plants form dense, slowly spreading mats about 6” tall, while others form loose clumps. The foliage disappears around the time that hosta leaves fully expand, and they make good companions.
A favorite short spring ephemeral. We had several plants of it growing under pine trees when we moved into our current garden. They emerge in spring with light reddish brown leaves that gradually turn green as the white star-like flowers open. They sprinkle their seeds lightly in the garden and never come close to being weedy. There is one humus-rich crevice in a large granite boulder where “someone” (an ant perhaps) has sown several dozen seeds that have sprouted and grown into an airy display. Not all forms have the reddish brown leaves – many come up green. We also grow the pink ‘Schoaf’s Double’ and creamy double ‘Cameo’. While these are very showy (and do not seed in), they can be difficult to find. Both the fancy and simpler forms of this plant are charming.
Dwarf columbines flower in May. The slightly blue-tinged 3-lobed leaves are very pretty even when the plant is not in flower. The inch-wide nodding flowers have a ruff of colored sepals, and wide-lipped petals with a backwards-pointing spur. The flowers come in shades of white, lavendar, yellow, blue and pink, and are often two-toned. They are easily grown from seed.
Variegated wall cress makes a very low carpet of waxy-looking green leaves edged with white. It is evergreen and thoroughly perennial, and good for filling in bare patches in the rock garden. It has heads of small white flowers in early spring.
Dwarf Goat’s-beard is a well-behaved, tidy plant with dark green ferny foliage, and will do a good job of filling in after the early ephemerals have gone down. It starts flowering in mid-June, producing many short spikes of small, creamy-white flowers. The foliage remains good-looking right up till frost.
Fumewort is ephemeral, flowering in early April, and disappearing by mid-May. It is normally grown from small pea-sized tubers, and comes in many varieties. The charming long-spurred, two-lipped flowers, varying in color from pure white to scarlet and purple, are densely packed on small spikes. Some varieties even have colored lips and white spurs. A very common form is a murky purple, and should be weeded out as soon as it appears, since it will cross-pollinate with the prettier types and produce dull-colored seedlings.
Dutchman's breeches comes up in early April, and is in full bloom by the middle of the month. It holds its dainty little panty-shaped flowers for about 2 weeks after that. The beautiful, finely divided foliage is very glaucous, getting a bit greener by the time the flowers are dropping at the end of the month. By the end of May, there is no sign of the plant, except for the funny little 1” ‘balls’ composed of small tubers, like a handful of small pinkish-beige peas all connected together. It’s not clear whether these are on or close to the surface when the plant is flowering, and become exposed when the leaves wither and disappear, or whether they have been pushed to the surface by voles. The tiny tubers can easily be separated and replanted.
This semi-dwarf form of the yellow foxglove flowers at the end of May, and the flowers persist well into June. If the bloom stalks are cut back, it will rebloom later in the season. This variety is shorter than the species, and has larger flowers, which are a pretty pale yellow on a one-sided stem. The leaves form a basal rosette of finely toothed, prominently veined mid green leaves. It is a short-lived perennial, and seeds around, sometimes rather too vigorously, but the seedlings are easy to remove. Similar to Digitalis grandiflora 'Carillon'.
Shooting Star has the look of a wild flower. The flowers are dainty and airy, and the leaves are low and stay at home. The usual color is a shocking pink with reflexed petals similar to its distant relative Cyclamen, and the flower stalk is usually 12 to 18 inches. There is a very beautiful white form that starts blooming around 6 inches and by the end of bloom reaches 18 inches tall. It seeds around mildly and creates pleasant surprises when new seedlings show up unexpectedly. I have seen Dodecatheon flowering profusely on the hills outside San Diego, CA in January. In Massachusetts it blooms in May to June.
Bishop’s Hat flowers in May, with flower sprays of up to 16” floating above the 8” leaves. The tiny flowers are white, with a touch of pink at the edges. The leaflets are medium-sized and bright green. The previous season’s leaves should be cut right down early in the spring, so that the new shoots will not be harmed.
There are many species of Coral Bells, and they come in various forms, but what people mostly grow these days are the hybrids. One of the very best is Heuchera ‘Silver Scrolls’. It is very hardy, and the leaves, which are silver with an overlay of burgundy when they first emerge, are netted with purple veins. As the leaves grow, the red flush disappears, and the leaf becomes almost silver and the veins darken to almost black. The mature plant is about 8” tall and 12” wide. It flowers in July, with tall airy panicles with many small, slightly rosy flowers.
The dwarf crested irises bloom in May. There are many selected cultivars to choose from. In this variety, the leaf fans are up to 8 inches tall, and the surface rhizomes spread rapidly to form a dense mat, which is covered in May by the dark violet flowers with their white signals and small gold crests.
This Japanese and Korean native is very happy under trees. It has light purple flowers that open early in spring. Occasional forms have dark blue-violet flowers. If the weather is cool, the flowers can last 10 days or more. If the weather is hot the petals can drop in a couple of days. The emerging leaves can be showy bright translucent red that shine in the garden when back-lit by the sun. With one clone of Jeffersonia dubia you will probably get no seed pods, seeds or seedlings. With two clones it seems that every flower forms a fertile seed pod, and can make seedlings as thick as turf. Individual plants grow slowly and do not divide easily, so if you want a big display, you have a quandary. While the flowers are held on 4-6 inch stems, the leaves eventually over-top the seed pods at about 12 “.
Spring snowflake flowers a couple of weeks after the snowdrops. The dark green strappy leaves are about 6-8 inches tall, and each flower stalk bears a single chubby white bell, with green spots on its tepals in the case of L. vernum var. vernum, or yellow spots, on a larger bell, in the case of L. vernum var. carpathicum. It self-sows but is not weedy.
Minoan lace flowers at the beginning of June. It is an annual, but it’s by far the prettiest of all the various lace flowers I have known. I don’t object to having it in the rock garden - it flowers for a long time, and it does self-sow, but is not weedy. The foliage is finely dissected and very insubstantial, and the flowers are the purest white. Instead of the umbel containing a mass of tiny flowers, all the same size, as is the case with most of the lace flowers, this one has what is effectively a double umbel. At the top of the stem, a set of smaller branches all of the same length each terminate in a much smaller umbel. This consists of a bunch of teensy flowers, where the 3 outer flowers of each mini-umbel have sets of two much enlarged petals, looking like little rabbit ears, and on the inside, there is another set of 2 or three much less enlarged petals. The whole effect is like a lace tablecloth.
There are several compact or congested Moss phlox cultivars, such as ‘Sneewittchen’, 'Betty', 'Herbert', and 'Sileniflora'. They flower in May, totally covering the low clumps of needle-like foliage with small pink or white flowers – a charming vision. They seem hardy here, looking a bit beat-up in early spring, but filling out nicely once any frost-bitten areas have been cut out.
The polyanthus primroses flower in May. These plants consist of a stemless rosette of green, tongue-shaped leaves. The showy clusters of 1 to 2” flowers are borne on short stalks from the center of the plant. The colors run the gamut from white to red, with yellow, blue and purple as well, and the flowers frequently have a contrasting central eye.
The exquisitely beautiful Japanese woodland primroses flower from the end of April and all through May and even the beginning of June. There are early and later flowering varieties, so there are always some in flower during this time. The flowering spikes are about 8”-12” tall with a cluster of flowers at the top of the stem. The flowers range in size from 1”-1.5”, and the colors range from pure white to vivid magenta, with a range of pinks and lilacs in between. There are many different flower forms – the petals are basically heart-shaped, and the edges may be smooth or may have various degrees of serration, from the very finest to deeply incised. Petals may be striped, or have a center that is a different color from the edge. In addition, the back of the petals may be a different color from the front. Despite their fragile appearance, these are amongst the hardiest of plants.
This low-growing tufted soapwort flowers in early June. The 1” long, dark green leaves grow in small tufts, and the short spikes of 5-petalled pale pink flowers, about an inch wide, cover the plant, making a very pretty show.
These succulent evergreen plants are grown mainly for their attractive foliage, and are most commonly known as ‘Hens and chicks’ – the rosettes of leaves multiply by making offsets, identical to the parent, and closely nestled beside it. There are many varieties with numerous combinations of leaf color – various shades of green and red are frequently combined, with red bases and green tips for example. The leaf color is most intense in the early spring, after which it fades somewhat but remains attractive. Individual plants of the S. arachnoideum (‘Cobweb houseleek’) types range from 1/2” to 2”, and the spidery filaments edging the leaves of the tight rosettes make a dense web in the center of the plant. The S. tectorum (‘Common houseleek’) rosettes are much looser in structure and can be up to 6” wide. When a rosette matures, several years after it is formed, it elongates itself into a stem topped with a cluster of starry flowers, usually pink, and then dies once the flowering is over.
This little species tulip flowers in early May. There are several different color forms, my favorite being ‘Bright Gem’, which is a pale butter yellow. It multiplies well as long as it gets enough sun. The only drawback is that when it goes down, the dying leaves look awful. However, this state doesn’t last very long, and you can cut the leaves down as soon as they are dry.
Bird's foot violet, so named for the shape of its leaves, flowers for 2-3 weeks from the second week of May. It has flat, 5-petalled blue-violet flowers, and though the plants are fairly small, a clump makes a good show since the plants are laden with many blossoms, almost an inch wide. These violets are somewhat picky about where they will choose to grow, but once they find a place they like, they will make nice clumps and seed around modestly.
The original document is available at http://nargs.org/nargswiki/tiki-index.php?page=New+England