Stachyurus soil trial

DSC06338Stachyurus Soil Trial Copyright.

Stachyurus chinensis soil, acid and alkaline evaluation

Kevin Pratt has asserted his right to be identified as the author of this work in accordance with the Copyright, Designs and Patents Acts 1988.

By K. Pratt

The Spike Tail, Stachyurus chinensis Franchet is a member of the family, Stachyuraceae. Stachyuraceae all come from Asia and Stachyurus consists of ten or eleven species.  Stachyurus chinensis  is an early spring flowering shrub from China, a plant which was first introduced to Britain by E.H.Wilson in 1908 but today is rarely grown in public gardens. As a genus, Stachyurus mainly resides in either specialist plant collections or botanic gardens.

Stachyurus have been notoriously difficult to establish after purchase. Death seems to be reported within two years and often contributed to either acid or alkaline soil conditions and frost. These following soil experiments were conducted during 2010, primarily examining soil expectation for the species S. chinensis.

Seventy-five S. chinensis, plants of garden centre quality (Fig 6), were purchased in the winter of 2009/10, three litres in size, fully pot grown, approximately two-three years old and stood 60cm to 90cm high but dormant growth due to time of year.  In the spring of 2010 before potting, the plants had finished flowering and were in full leaf. Ten plants were selected at random and planted into 10 litre pots, using the compost mixtures below. Each group of ten plants were divided into seven different compost mixes and all grown in exactly the same eternal conditions, light shade, no direct sun, watered regularly but no fertiliser was used. The plants were spaced fortnightly and turned weekly; the growing plants were allowed to grow during the summer all regularly monitored and maintained. All the plants were grown at my garden in Stockport, East Cheshire in the North West of England, United Kingdom Latitude: 53.4 / Longitude: -2.15 / Altitude 70m (210ft) Average Winter low temp of -5°C, Average Summer high temp of 25°C. (However the plants did suffer -18°C in January 2010, a warm spring, and a drought of twelve weeks 2010 with summer high of 38°C.)


The composts:

(1) Ericaceous compost. Absent of lime, an acid soil with a slow release nutrient, bought compost.

(2) John Innes No2 compost. Alkaline soil, mixed with my good garden loam soil, low in slow release nutrient.

(3) John Innes No2 loam. Alkaline soil with a slow release nutrient.

( 4) My spent compost of waste soil, gritty, well drained, no nutrient.

(5) Bought compost “Levingtons” brand. 100% peat with lime added and slow release nutrient.

(6) Bought compost Miracle-gro with ‘wetting agent’ to prevent drying out, with an added slow release          nutrient.

(compost 7) Bought compost a compound of 57% peat compost 43% loam with added lime.

These following notes were taken at the beginning of November 2010.

The Results:

Compost 1 (Ericaceous compost.) By autumn 20% of plants died. All the plants had good root growth with each of the pots completely full roots to the bottom. Although the root growth was good, conversely the top growth was relatively poor with a large number of leaves falling off in early October, at the first signs of chilly autumn weather. The stems were thin and spindly in comparison to the other plants, the thin top, new growth had a few leaves but with some 50% of the stems losing all the leaves. Looking forward to positive points, some 90% of the plants did actually produce flowers and these were of reasonable good length.

Compost 2 (John Innes No2 compost mixed with my good garden loam soil) 0%, none of plants died, all lived. Plants doubled in size and made very thickly set stems and growth, each with good pencil thick stems and large deep green leaves. All plants have one to three 1m stems of new growth and the pots were completely packed full of roots. Handling and carrying was more labour intensive due to the heavy compost, watering during the dry spell was more laborious and leaves showed more signs of stress than other plants (logically with stomata closure, growth would have been impaired.) My expectation during the summer was a yield of poor plants, this expectation was premature, because all the plants survived and all made exceptional plants. 100% of the plants formed good, long spikes forming with all holding a superb set of awaiting flowers. This seems a good soil mixture if not for the extra work involved.

Compost 3 (John Innes No2 loam) 10% of the plants died before autumn. These plants were again good thickly set plants with good deep green leaf cover. The plants had doubled in size but the foliage of all these plants showed signs of abnormal early autumn leaf yellowing, I suggest this was due to the soil nutrient reserves becoming exhausted. This autumn colouring was not unattractive and would not have stopped the sale of the plants. All 100% of the plants were in the process of producing a good set of flowers. This seems good compost, but like the last, this too was heavy to move around.

Compost 4 (my spent compost, waste soil, gritty, well drained, no nutrient) 80% of the plants died before autumn. This felt like an incredible waste of such good plants and a very disappointing compost mix. It was soul destroying to watch the plants die one after another. The deaths started during the dry spell, wilting followed by recovery only to wilt again the next day. Die back of the stems followed shortly after the wilting (Fig 5,) this stem blackening would continue down the stems towards the base. There was also a feeling that the plants were starving of food, chlorotic leaves, poor growth, loss of older leaves and smaller than usual new leaves, with obvious signs of necrosis. All this was again followed by die back of the stems. Of the very few survivors, these were poor, spindly with small leaves and no flowers, these were not saleable plants.

Compost 5 (Bought compost Levingtons brand) 30% of the plants died before autumn. Plants were fully rooted throughout the pots. The plants had strong growth with good deep green leaves. The nutrient seems to run out before the season close. All the plants showed signs of die-back (Fig 4,) started during the late summer suggesting that die back could be due to either drought or certain nutrient deficiency.  80% of the plants produced a good set of flowers.

Compost 6 (Bought compost miracle-gro with wetting agent to prevent drying out) 20% of the plants died before the autumn. Due to the wetting agent, logically the compost needed loss watering and care, adversely during wet period it was worrying that compost remained wet all week. The growth was loose and spindly, often with many bare stems or with only 50% leaf coverage. All the plants had almost no new growth, so logically less that 50% of plants produced flowers. As saleable plants these were poor, although fully rooted the plants would need to be grown on for another year.

Compost 7 (mixed compost 57% peat compost 43% loam with added lime) 0% of the plants died before the autumn. These plants were spectacular plants which stood out from all the other plants. It was possible to look at any plant amongst the collection and realise it grew in compost 7. All the plants have doubled in size with two or three  1m new growths on all plants. These were very leafy, deep green plants with strong, pencil thick stems. The pots were fully rooted in the compost. These sizable plants could easily be sold as mature 1m specimens and would recoup any losses. From the spring the plants began to grow strongly, producing thickly, bushy plants even during the dry spell. There was only one drawback. The plants only produced 20% of flowers, however they were extremely healthy plants.


Conclusions were aided at the end of the trial by a simple awarding of points during the season (Fig 1-3.)  A scale from one to five was adjusted in favour of the performance.

Generally Stachyurus do not like to be excessively dry, fluctuations in Dryness, temperature and environmental conditions also affect the growth. Die back occurs often during the spring and often after late frosts but also during the summer drought. Once the leaves are damaged wilting begins followed by the beginnings of die back. Once the wilting starts no amount of watering or rapid healthcare can halt the certain following die back.

The suggested appropriate soil for Stachyurus would be a well-drained garden loam or John Innes compost with lime, not as suggested in most articles; Stachyurus do not need ericaceous compost, adversely as it affects the growth during the season.

Kevin Pratt 2011

5 thoughts on “Stachyurus soil trial

  1. Thanks – interesting to read your trial results and explains the sensitivity of not just this plant but others to the medium you put it in. Helpful to an amateur gardener. Thank you.

    • Hello Arabela
      I remember chatting to you in London and meeting you in the garden with Lord H. Cavendish.
      I have indeed written the monograph on Stachyurus but I’m a long way off printing. There are so many updates and I still want to complete my tour of UK visiting all the growing plants in UK. There are so many species wrongly named plants and a few interesting unusual early collected forms that are planted in botanic gardens.

      How can I help you?

      Sent from my iPod

  2. Thank you, that was a wonderful read and such an interesting study. I am a keen gardener who has recently changed career from the office to the outside. Currently studying RHS and completing a WRAGS scheme. Will be up your way next week and our Head Gardener Sharron White suggested I came to your nursery. Hope to see you next week. Esther

  3. Wow! Can’t ever remember reading such an objective, dare I say scientific, gardening article. It’s so hard to get good information from the web. Interesting, as Stachyurus is always noted as being suitable for acid soil. I guess what I take from your report is that improving soil and providing a good growing medium, is worthwhile. I am planning to plant a few Stachy.. and Coryolopsis on a poor, pebbly soil, similar to acid heath ‘soil’. thanks for the advice, know what I need to do this month…. improve the soil in the area I’m going to plant in!

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