Plant of the Month: June

Thalictrums

by Sue Gray

Thalictrums are a genus in the ranunculaceae family, with approaching 70 species, plus varieties, listed in the Plant Finder.  Crug Farm is particularly noted for them, with many listed in Plant Finder bearing the detail ‘B&SWJ…’ indicating that the plants originate from seed collected by the Wynn-Jones.  I have to admit that I have had one or two such, but have had great difficulty distinguishing them from the more usual varieties of T. delavayi, but that might just be me!  They are such useful plants for the summer garden, with varieties ranging in size from the diminutive T. kiusianum, just a few cms tall but which many people, including me, find very hard to keep, to the statuesque ‘Elin’ or its descendant ‘Anne’, both of which can reach about 2.5m, but do not normally need staking.  Most have flowers of mauve or white, but there are the forms such as T. flavum which bear creamy yellow flowers above grey/green foliage.

Thalictrum isopyroides

Usually the foliage is green or grey/green and, whilst there is a particular species ‘aquilegiifolium’, in general the leaves are aquilegia-like and can be very dainty, resembling Maidenhair Fern, as seen on T. isopyroides or ‘minus’ where there is a variety named ‘Adiantifolium’.

  

Thalictrum ichangense

However, some varieties have slightly larger, and in the case of T. ichangense, distinctively marked, more heart shaped leaves, which sets off the delicate, fluffy flowers.

Thalictrum delavayi

One of the most often seen species is T. delavayi AGM.  We are familiar with the species name ‘delavayi’ being attached to a number of different plants.  It is derived from Fr Jean Marie Delavay; he was a 19th century French missionary and botanist who spent a lot of time in China from 1867 until his death in 1893.  In 1881 he met Fr Armand David – from whom we get ‘davidii’ – who had made his last plant collecting trip to China in the 1870’s, and who encouraged Fr Delavay to continue collecting plants for the Paris Museum of Natural History.  This he did and he is credited with the introduction of around 1500 new species.

Usually seen in the familiar mauve form, there is a white form, and a number of forms introduced by the Wynn-Jones, also the double form ‘Hewitt’s Double’ with smaller, daintier, flowers.

I find T. delavayi can seed a little in the garden, but is always welcome.

Another species that can self-seed a bit is T. aquilegiifolium.  It can grow to anything from 1m-2m or above and is wonderful for summer colour in shades of mauve and white and, as the name suggests, has the most aquilegia-like foliage.

Thalictrum aquilegiifolium

Many of the recent named forms of thalictrums are varieties of this species, such as ‘Thundercloud’ AGM.  I remember seeing a spectacular plant of ‘Thundercloud’, with wonderfully vibrant flower heads, on one of our garden holidays, but attempts to source and grow said plant have had mixed results! A ‘Small Thundercloud’ has been introduced and the distinction is not always made on plant labels, so, buyer beware!                         

When asking about ‘Thundercloud’ at Dove Cottage, I was told that they felt that ‘Black Stockings’ was actually a better option, and it has certainly become very popular with its black stems.  Sadly mine has suffered a terrible attack of aphids & blackfly this year, which has never happened before, so I have cut it down and am hoping for the best.  Should it not recover, I will definitely want to replace it, as I agree with our friends at Dove Cottage.

Thalictrum ‘Nimbus’

Another relatively new form of T. aquilegiifolium is ‘Nimbus’.  Again, the almost black stems contrast beautifully with the mop of white flowerheads, which are loved by bees.  In his RHS blog, Graham Rice speaks of it as follows: ‘Thalictrums have never belonged to the bestselling rank of hardy perennials, but Thalictrum ‘Nimbus White’ might just change that.’

From the internet I see that there is also a pink form that I will want to seek out, and should it be as good as the white form, will hope to add to the collection!

There are so many species of thalictrum but just to mention two other forms that are rather special.  I have, in the garden, the usual form of T. tuberosum, standing to about 35cms topped with small white flowers.  However, there are some very special forms with much larger flowers.  Those with good memories may remember the plant loaned to us by Bob Brown for our Chelsea display in 2010, which he had bred and named ‘Rosy Hardy’.  He has tried, unsuccessfully, to propagate this plant – if he could do so there would be a long queue of customers, and I would be at the head of it.  It has appeared in his catalogue on occasions, and I have tried to buy it, but the young plants have never survived at the nursery.

Thalictrum diffusiflorum

Another absolute beauty, which I have had twice, but alas no longer, is T. diffusiflorum.  Only growing, in my experience, to about 45cms, the large, intensely blue flowers can almost seem too heavy for the wiry stems.  Elizabeth MacGregor, who sells it from her nursery, recommends keeping it in a pot rather than the open ground; I think the longest I have ever had one is 3 years but, it was beautiful while it lasted!

So, just a small selection of the many forms of this most wonderful and versatile genus, which I hope you will enjoy in your garden.

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