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This stately and hardy family of unusual plants is the central theme of our garden, hence I will provide a somewhat more extensive commentary on them. The Thalictrum genus contains about 150 species in North America, Europe, Asia, Japan, South America, Tropical Africa and South Africa. It is probably the most widely spread of the Ranunculaceae and one of the only that can tolerate a tropical environment.  Their airy appearance is rather "sub-tropical," and lends an exotic, fantasy element to the garden.  Most of the species produce clumps of herbaceous stalks similar to a columbine, but their size ranges from three inches to eight feet.  There are recognizable traits common to the species.  If you like the foliage of a columbine, you'll really like the thalictrums.

To give a simple description, imagine a tall, stout-stalked columbine which has flowers that open from spherical buds to reveal a plethora of stamens. The petals usually drop, except for the tall Japanese species t. rochebrunianum, and the Chinese t. dipterocarpum.  With a couple of exceptions I know of, they are fairly tall plants.    It is rarely necessary to stake thalictrums, except for the local tall meadow rue, or dasycarpum species, which I do not recommend anyway.  The local T. dioecus is much more beautiful, and shorter--only about 15"-24".  Found most often in the wild in wooded ravines, and drainage ditches especially near limestone.

I replaced my T. dasycarpum with the Japanese variety because the T. dasycarpum just isn't very attractive as a garden resident.  I don't feel guilty about cultivating the alien because it is less hardy here, and blooms much more profusely for the benefit of bees.  The taller local species is a remarkably prolific self-seeder.  The flowers last about one week under good conditions, and the foliage is fairly weedy in appearance.  Picture lots of floppy, thin stalks about 6 feet high, and dark green leaves that could only justify their presence by producing something tasty or useful.    

There are four general classes in terms of the foliage (in my opinion): 

• the rugged, glaucus T. flavum from Spain, which almost doesn't look like a thalictrum.  This is an excellent decorative meadow plant.  In Minnesota it is marginally viable, so it isn't dependable enough to make into a pleasant denizen of a smaller garden.  I think that it likes a drier soil than it gets in our garden.
• The delicate and beautiful Asian species.  These are the most exotic, and most sensitive to water/heat conditions.  They are also preferred by aphids and caterpillars.  Not recommended for lazy gardeners.  However, the T. coreanum is excellent and easy, provided it gets reasonable watering.  Interestingly, I've noticed that T. rochebrunianum likes black soil with some clay content, even in fairly dry conditions if protected from intense Summer sun. 
• The airy but simple North American species.  Trouble free, except for reseeding.  They all have male and female plants, the males being the most attractive.  These are the easiest to grow.  Generally, the shorter the species, the more desirable.  The European T. minus is similar in appearance, judging from the nursery plants I've seen.  However, they spread by rhizomes underground.  
• The European T. aquilegifolium is the species I most highly recommend for its combination of durability and beauty.  It is more rugged in appearance than the Asian species, but less prone to pests and disease.  They are also tougher than the t. flavum, which tend to decay like columbines after blooming.  T. aquilegifolium has a unique tissue structure I call a "valve" at the joints of the tripartite leaf stems, which helps identify its seedlings from the T. rochebrunianum and T. flavum.

In general, it would appear that they thrive in areas with snowy winters and wet, cooler summers. Some species, like the T. rochebrunianum, require careful watering and special conditions of light and soil. 

They have a reputation for not liking cold winters, but I suspect that hot, humid, sunny summers without rain and dry winters are more likely to kill them. I do not think that any of them will do well in dry conditions, but the North American spp., as well as T. flavum & T. aquilegifolium seem to be less demanding of water than the others.  Surprisingly, they are often listed in gardening books and catalogues as being hardy in USDA zone 6, I am convinced that you cannot kill them even without mulch in zone 4. What kills them is either drought or crown rot.  All Thalictrums appreciate light, but do not like a lot of strong, midday sun  Bright shade is an ideal location.  I don't think they will do well in poorly drained soil, but I'm not sure.  They do pretty well in containers, but it keeps them small.  

The local species thrive in drainage ditches next to converted railroad bike paths in several locations in Minnesota.  They seem to like to grow on the north sides of fairly steep slopes where ferns also grow well.  They are often found on rocky river bluff sides in Minnesota and Wisconsin, though I have never seen them in Iowa.  

Most meadow rue produce sprays of individual flowers no more than 1/2" across. The species native to North America are gendered. Those of Asia and Europe are not. To my knowledge, the gendered nature of the American species is unique in the entire ranunculaceae family. The female flowers are unremarkable, but the seed heads are respectable in a perennial garden. The male flowers are really beautiful from close up. They possess pendulous stamens, acid green to yellow.  They look to me like beautiful, dangling tassles on the edge of a yellow silk scarf.  Unfortunately, the flowers are short lived, and fall entirely away from the plant, leaving no trace of flowering. They look at home in Minnesota woodlands, especially in areas where Maidenhair fern thrives. 

Several other species have no petals, but have more puffball-like structures of stamens. T. flavum has fragrant flowers (relatively unusual in the Ranunculaceae family) that are the glory of an evenly moist, sunny garden. Bees seem to behave as if intoxicated as they plow through the fluffy chartreuse flowers.  It seems to draw all the bees in the neighborhood to it, to the neglect of the other flowers in the garden.  It is a very powerful "bee magnet."  This plant has a unique beauty, but I recommend planting it behind a plant that gets about 18" high.  It's an excellent background plant.  The foliage is quite interesting, and works nicely in flower arranging.  After flowering, mine consistently succumb to some sort of insect like thrips, or a fungus.  It's not clear to me.  The first couple of years I had no troubles, but they just don't make it to ripening the seeds any more. 

In the formal garden, the Asian species make wonderful background plants. I can envision T. rochebrunianum used as an airy wall in an elaborate Japanese garden. In front of them, some oriental lilies such as 'Marco Polo' , in the center of the display, several Fritilaria persica, . . . They are traditionally used as a foil for delphiniums. A photo of Monet's garden I saw once showed T. aquilegifolium planted at the edge of a scenic pond. The T. rochebrunianum and T. aquilegifolium and T. delvayi and T. dipterocarpum are excellent for creating an "oriental effect" in a garden. T. Flavum would be an excellent prairie plant as well as a fabulous companion to just about any plant in the less formal garden. None of them except perhaps the T. aquilegifolium is suitable for very formal gardens. They draw your attention by their overall form, not from the flower. All but the alpine species are very difficult to photograph (and capture the effect). Most have strongly vertical stalks, airy leaves divided into complex, symmetrical patterns of three with delicately incised leaves. Smaller shade-loving species are indispensable for filling in wooded shade gardens and rock gardens. The T. kiusianum is a fabulous plant, and the flowers last and last.

If you would like to see illustrations of these beautiful plants, send me an e-mail, and I'll send you some photos. 

They make excellent cut flowers and even the foliage is fabulous in flower arrangements. Although all Thalictrums make good cut flowers, only the Hewitts Double and perhaps the Rochebrunianum are usable as dried flowers. Only the Yunan Meadow Rue (T. dipterocarpum), the rochbrunianum and 'Hewitt's Double' are really spectacular enough to be grown strictly as cutting flowers. The Hewitt's Double is to the Baby's Breath what triple cream brie is to Velveeta. The 'Hewitt's Double' dries splendidly. T. flavum does not make a very attractive cut flower, but it does have a pretty nice fragrance.  I would imagine that cutting the stems right before bloom would be the best way to take them.  The somewhat gnarly stems would add some visual interest to a bouquet.

Propagate them by seed or division in early spring. Seeds are actually quite easy to germinate, taking about 2-3 weeks.  If they are in a sunny location, give them more water, but beware of over-watering.  Crown rot is fairly common. Their natural habitat is in meadow-forest transitional zones where moist, rich, well-drained soil is found. They do not appreciate clay or peat moss although it appears that given good conditions in other factors, they can do quite well with a bit of each. Leaf mould is another important element in their culture. I mix half rotten maple leaves that were used as winter mulch into their soil. I give them plenty of composted manure, bone meal and decayed leaves from the previous year. Make sure they are well-moistened when the ground freezes hard. In early November they can be cut down and mulched with an airy, but moisture retentive mulch like mowed leaves. Winter snow cover assures their survival even in the Twin Cities.   Yet, after eight years of cultivating them, I have become progressively lazier in protecting them.  At this point, the only plants I actually put mulch on are the heathers.  I leave the meadow rue to fend for themselves, and none of the species has shown a loss of vigor for the neglect.  I have given them to many friends, none of whom mulch them, and all of whom report that they are thriving.  In other words, all the hype about zone hardiness and thalictrums is a bunch of crap.  Water, heat and light are much more critical factors.

They are surprisingly trouble-free, though the T. rochebrunianum is attractive to phytophagous insects like thrips, and the T. flavum is vulnerable to mites at the end of its bloom cycle.  Be prepared to spray and/or destroy the entire plant (above the ground--it will come back next year).

Propagation seems easiest by sowing seeds in situ in the fall--or simply letting nature take it's course. Remove seed heads to control reseeding. They are easy to control (though I hear the T. minus, a smaller, ground covering species, is rather aggressive.)

A young seedling will not bloom, but will reach about 10".  The second season will produce a somewhat tall and thin stalk with a few large fronds of leaves, similar in form to the Cimicifuga spp. A second stalk may develop.  This one will flower.  The third year brings an adult plant with a stout stem.  When you first buy them, it is probably advisable to protect them carefully in their first year and stake them in their second. By the third season, they will begin to spread, forming a clump of four or more primary stalks.  They will also start reseeding.  At that point you will notice that you are putting more energy into controlling them than into protecting them.  In the larger species (T. rochebrunianum, T. aquilegiifolium, T. flavum) these stalks will be rather fat and beautifully colored, making the growth of the plant itself an impressive sight long before the flower stalks emerge. The rochebrunianum and aquilegiifolium sport luscious green stalks with the most beautiful shades of deep purple tint. Sometime in late May, the aquilegifolium will be the first to send up its almost black-maroon flower stalks. Spring bulbs look marvelous in their presence. Jack in the Pulpit is a unique companion to the T. aquilegiafolium.

When purchasing delvayi 'Hewitt's Double' and dipterocarpum, you should bear in mind that these more fragile plants do not emerge until mid-May and a hard-wintered plant in a gallon pot may look like a dead plant.  Garden centers often sell hothouse grown ones that are already blooming when you buy them.  In natural conditions, or with plants that have been wintered outdoors in pots, you'll want to wait until about June 1 to decide whether to spend money on it.  The following season, avoid poking around to look for the shoots, the first ones may not appear until after tulip time whereas the flavum will be noticeable before the Equinox.  'Hewitt's Double' is worth all the trouble if you are a careful gardener.

Their airy habit and dense mass of tiny leaves endears them to me almost as much as the larger species. The flowers are like lavender Baby's Breath (gypsophylla spp.) only far superior. In spite of their fragile stems and slow start, these are vigorous growers and will send up a dozen or more stalks in their third season. It also has the advantage of remaining under four feet. Be sure to acidify the soil slightly for the Hewitt's Double.

The family includes the following less garden-worthy species: rotundifolium--single round leaflet. T. minus or adiantifolium has great foliage, but dull flowers. It is very invasive--not recommended for planting in areas where they will do well.

Small garden shops  rarely carry any Thalictrum. Expect to pay at least $8.00 for a plant at larger nurseries, or specialized boutiques, and native wildflower suppliers.  Once yours are going, you'll be forcing them onto your friends and neighbors.  They are easy reseeders.

There are also a number of unisex-flowered species native to North America. The male plants have the most interesting flowers. They are not as attractive as the previously described species. They include the Tall Meadow Rue Polygamum, that is too large for residential gardens, but a lovely addition to reconstructed meadows. It has white flowers. Dasycarpum is similar but only 3' tall.  T. dioicum or Early Meadow Rue is a diminutive, fragile denizen of shady forests. Its pendant chartreuse stamens are lovely. It is a vigorous self-seeder. All of these are quite common in the Minnesota woods and meadows.

Alpine dwarfs such as the T. alpinum also exist in Europe, Asia, Greenland, Newfoundland, Alaska, Quebec, to New Mexico and California. They look much like the T. Dioicum or a tiny T. Delvayi and have greenish sepals. The most desirable garden species is the Japanese Kiusianum. It spreads underground, an unusual characteristic in this family. These appear to be splendid ground covers for oriental and trumpet lilies. (Asiatics and day lillies are surely too aggressive for this purpose.)  It would also probably work well around a clematis to keep the roots cool.

The hybrid aquilegiafolium and 'Hewitt's Double' (2'-3') will make pleasant middle range plants that look lovely with hostas, astilbes, goat's beard, hardy geraniums, and any other plant that can contrast sharply with its airy, smooth foliage. Currently we are planting the taller species in alternation with large dahlias along a 25' stretch of chain link fence. They are shaded in the morning until 10:00 AM and in the afternoon after 2:30. Hence, they need extra water, but seem to be thriving.

All meadow rue have fleshy roots that can be transplanted easily, and divided fairly successfully. They are not taprooted like Columbines.

For transplanting and division, I have found that it is best to dig the plants, pot them in moisture retaining, fertile soil, and then water them heavily.  I then leave them in the shade where almost no sun will touch them for three days.  The taller stems will almost certainly wilt, and may even die back.  That's ok.  After a few days, the plant will stabilize  and you can plant it.  Don't allow new transplants to get dry until they have had another week or two to get their roots growing.  This is especially critical with the T. rochebrunianum, and somewhat so for T. flavum.  The other species seem to be unharmed by careful digging and division.  These are definitely not fragile roots.