Growing Media


Welcome and introduction

Welcome and introduction

Harvey Stephens, Head of Savill Garden

Related Presentation

Welcome and introduction

Welcome and introduction

Harvey Stephens, Head of Savill Garden



Cambridge University Botanic Garden

We have a standard pre-made, General Mix that is purchased from Petersfield. We also buy in a range of individual components, which are used to create bespoke mixes for particular plant groups. These range from fine-grade and medium-grade barks, to charcoal, pumice, grit, coir, perlite, etc., and are combined to fit the needs of the grower.

Under glass, the main groups that we prepare (or have prepared) specific mixes for are orchids, cycads, palms, carnivorous plants, Amorphophallus etc.

With regard to difficulties, at the moment we are very interested in creating a suitable Arid Mix (for general purpose use).


Chelsea Physic Garden

We do our own mixes: one for cuttings and one for seed sowing.


Eden Project

Here at Watering Lane Nursery, we use a Melcourt peat-free product for all out potting needs. As you may imagine, we grow a wide range of species without too many difficulties. However, we hope to be testing a seed-sowing peat-free mix in the coming season and, like many people, we would be interested to hear more on work towards an ericaceous peat-free mix.



We have for a long time made up our own potting and growing media, but recently have started using Melcourt Sylvamix ‘Natural’ for some of our nursery production.

We still make ‘special’ mixes using leaf-mould, shredded composted bracken, composted wood-chip, our own garden compost and turf loam. The main problems we have are consistency of mix and issues with addition of nutrients to the mix (being organic); we use granular seaweed and blood fish & bone for longer-term potting mixes. Locking up nutrients and the build up of salts in the medium are two problems we have encountered, as well as trying to keep the medium ‘open’ enough for decent drainage and root establishment.

We still use finely sieved leaf-mould and grit for our cutting and seed-sowing mix and find it very successful.

We have always had problems with creating a successful mix for citrus, though now have some good information from the lovely people at the Citrus centre in Sussex.

We have had some excellent results growing on young Acer palmatum in a mix of composted shredded bracken and loam.

We bought in a batch of wood-fibre base compost (not from Melcourt) which introduced scarid fly, which we have had a minor problem eradicating (using biological control methods).


Ness Botanic Gardens

The one group we struggle with are peat replacement mixes for our ericaceous plants.


Osborne House, English Heritage

We have been using a coir-based compost from Sinclair for many years, with good results. It has different watering needs, so you have to get used to that and it doesn’t hold onto nutrients that long, so it’s no good for long-term pot plantings.

We also produce our own garden compost, which once shredded and sifted, is a very usable product. We have used this to help retain more water in our small vases on our balustrade (mixed 50/50 with coir) and in some of our longer-term pot work. It also seems to have more nutrients, so we pot our cannas into it, as they always seem hungry plants.

Other than that, we only add vermiculite to coir to make cutting/seed compost. Most of the plants we grow are fairly standard, so tend to grow well with us.

I’m still a fan of John Innes. It’s just so much heavier, which is a bit of a manual-handling concern with some of our big pots.


RHS Garden Wisley (propagation)

We struggle to grow Meconopsis, in particular M. betonicifolia in pots.

We also propagate some woody plants from semi-ripe cuttings, which root easily, but then struggle to establish themselves in pots. I think this may be partly down to the growing medium. Desfontainia and Crinodendron are two that spring to mind. I heard that reducing the phosphate levels can help.


Royal Botanic Gardens Kew

At Kew we buy in 5 different basic mixes from Petersfield. In Alpine we use just one of them (very similar to JI No 2 or 3 perhaps) and then make up ‘bench mixes’ adding more grit/coir/leaf mould to suit the particular group of plants.

Most of our Alpine collection grows reasonably well, but for some time I have wanted to experiment to achieve mixes that perform better. However, with such a range of taxa it’s difficult to know quite where to start. Our Tropical nursery has looked at the amount of water different mixes hold.


Savill Garden

We mainly use pre-mixed composts, adding sharp sand or slow-release fertiliser as necessary.


Sir Harold Hillier Gardens

We worked with the company Vital Earth, to make up our general potting compost. The basic content is composted bark, as a replacement for peat. Within this mix is the fertilizer and insecticide. It has worked pretty well for us. We use a special ericaceous mix for rhodos etc., but we don’t know the content, as the company keep this secret! Seems to work though. We still use a small amount of peat for seeds and cuttings.


University of Oxford Botanic Garden

We used to make our own John Innes mix, but then had our compost mixed by a local supplier. We now use Petersfield Peat Free Supreme compost for general repotting.  Petersfield is a really good general mix for plants that are being potted on quickly – our hardy team find it particularly good. We may well try their John Innes peat-free compost next year as we are finding some of our tropical stuff is a bit too hungry for the peat-free supreme.


Wallington, National Trust

We currently buy in our peat-free compost. However, we are constantly experimenting with our own garden compost to make that suitable for potting.

One area we are not happy with is in our conservatory, where we have all kinds of tender specimens, and the various composts we are using don’t quite hit the mark for plants that are in pots for a considerable time.

With some hardy perennial crops we grow, we have problems with yellowing foliage at certain points in their growth (this is using a bark-based compost).

We are also after a good ericaceous compost for nursery production.


Welcome and introduction

Welcome and introduction

Harvey Stephens, Head of Savill Garden