Traditionally horticulture has been served with massive choice. Not least in the various potting container sizes available to it.

Statement: Wetland marginal plants should be grown to a known specification.

That stated, the question is to what specification? What do we need in a plant and its root system that will make it ‘fit for purpose’?

Reeds (Phragmites australis) and reed beds are an example. In the early days of the 1980’s reed beds were virtually unknown in the UK. The early growers of Phragmites would have looked around for a commercially produced pot size to raise the crop. At that time the Plantpak Company in England produced a P7 or FP7, for use in production within the bedding plant sector of horticulture. This pot was the metric equivalent of the 3 1/2” flowerpot of old, made of clay. Modern process of course now manufactures in plastic. It would have seemed a good ‘rootball’ full when these young reeds filled the pot with roots.

Thing is though we are mixing metaphors here. We are talking about 3 1/2” pot, metric equivalent, 7cm across the top of the pot, but this does not tell the whole story. What about the actual size including the depth? Various pot manufacturers extrude various depths of pots, but all pots have one thing in common, volume. We can directly compare what the difference between nurseries and their offered plants, and the volume they are growing in.

But is that the whole story? we need to know that a particular volume = sufficient and hardy root systems.  Let us turn to the plants, of Phragmites australis (Common Reed), and also, Typha latifolia (Reedmace). What constitutes a mature, hardy, saleable, plantable plant?

1. Age from potting on. (Potting off is potting up from tiny to larger, potting on is finishing into a final container, (of whatever size)).

2. The plant must have grown sufficiently long to a), develop a good and full root system, and b), be of an age where it is hardy to survive the shock of transplant into a new growing environment. As a rule of thumb, this is gardening, not rocket science! The plant should have nearly trebled its root system by the time of planting. In time this means that plants potted on in the Spring should be ready for planting before the onset of autumn.

3. There must be sufficient volume in the container for the root system to be fit for purpose in the planted situation. In other words, a plant planted into a stone surface of a reed bed must be physically large enough to be able to survive.

4. The roots should have developed, and filled up the available space in the volume the pot offers. In those such plants where they occur, rhizomes the underground structures which run out sideways and come up in a different place away from the mother plant and form new plants growing, should also be developed within the root system.

So how should a contractor know what to specify, he needs to specify correctly to the nursery both in getting the right size, and age, to avoid too young plants arriving on site. Once again there are no hard and fast rules to apply here.

The plant should be supplied in sufficient volume for its eventual and new surroundings. Most stone reed beds demand a size of plant to go into a between 14mm to 20mm washed gravel.

Better that a minimum size say 125cc to 300cc (notice we are now talking in pot volumes). Habitat creation schemes requirements are different only in so much the plant is probably specified as a bigger size,

and that it should have been growing for at least X months. X months is probably not less that 11 months. Once planted it is a brave new world for our fledgling seedling.

To be able to grow it has to be undisturbed for as long as possible before handling. Consultants often specify overwintered plants in the design for this very reason.

Do we need overwintered plants?

Well the advantage is that these plants have been growing for some time in a nursery bed and can be deemed to be hardy having spent most of the winter at the nursery. But what happens when the nursery sells out of overwintered plants, and the spring is only yet upon us, can we still plant something? The answer is yes! We don’t know exact aging to hardiness ratios, plants potted up and grown on, can be ready sooner that we might think. There are general guidelines. Plants planted should be not be less than 6 months old. Rhizomes should be present even in small numbers. As long as these rules are agreed to we can plant with confidence.

Pot volumes are the most accurate indication to buying like for like in plants. If you get a quotation for a plant, overwintered, hardy, well rooted. Against a quotation for the same plant, same age, but higher price the likely difference is going to be age and volume. The smaller the volume, the smaller the footprint on the ground. Overheads to a nursery are costed out in square metres! Hence higher end unit price. Next time you require a quotation for plants try thinking volume for better like for like comparison of quotations.

9cm         9cm          7cm   125cc