• AGM plants

    AGM plants have been through a rigorous trial and assessment programme. They are:

    • Excellent for ordinary use in appropriate conditions
    • Available to buy
    • Of good constitution
    • Essentially stable in form & colour
    • Reasonably resistant to pests & diseases

Meeting garden royalty

An RHS Plant Trial explores the charms of an under-appreciated genus

Thalictrum delavayiThe Trials at the RHS have been extending their reach to other parts of the country recently. In January I visited the Hamamelis trial in Sittingborne, Kent. Now that the better weather is here I have been travelling to Wales for meetings of the Thalictrum Trials Assessment Forum.

Aberglasney Gardens in Camarthenshire, an RHS Partner Garden, is hosting this intriguing trial for us. Their Head Gardener Joseph Atkin proposed the trial in 2011 and we are now in our first year of assessment after an establishment year.

Thalictrum are an under-appreciated genus of huge variation in height from 10cm (4in) to 3m (10ft). Although there are many alpine species the plants in trial are moisture loving perennials with grey-green delicate foliage and airy clouds of tiny petal-less flowers, the stamen providing colour. We have 70 entries in the trial which can be found in the walled garden, usually used for fruit, veg and cutting plants.

The trial was planted in April and May 2012 with some latecomers in the autumn. The Forum are assessing under the following criteria; floriferousness, flowering period, flower quality, foliage quality, form and habit, self-cleaning, pest and disease resistance and vigour. There are three plants per entry and two of these are being staked with one left to see how well they self support.

Thalictrum 'Tukker Princess'The climate at Aberglasney is very different to Wisley receiving on average 2000mm (79in) of rain every year. Runoff channels can be seen around the gardens to allow excess water to escape. The garden is also cooler than Wisley, however this last visit was sunny and warm in the middle of a dry patch, which has meant that irrigation had been used on two occasions.

After only two meetings, the Forum have been impressed with the performance of most plants. One plant that made an impression on me was Thalictrum ‘Tukker Princess’ (right). Currently at about 8 feet (2.4m) tall I’m told it will only get taller; its bright yellow flowers at the top of stripy stems.

More from the RHS

Plant profile: Thalictrum delavayi

Plant profile: Thalictrum flavum subsp. glaucum

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