Larry Smith and the Riverside Gardens team talk all things pots, plants and pruning in their weekly gardening column.
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This week we started potting all our bare rooted deciduous winter stock, starting with the bush roses and moving on to the standard roses.
Next week we will start tackling the deciduous ornamental trees and fruit trees.
It is a busy, but enjoyable time for our crew, as they put their horticultural skills into the task at hand.
Trimming roots, pruning the branch structure, potting up into the appropriately sized pot or grow bag, feeding, tagging, watering in and then spacing them out to grow.
To do all this successfully, efficiently and with due care is a skill that often goes unnoticed until people try potting up something at home.
This got me thinking that it is also a skill that we as nursery people all too often just assume that our customers know when they head off with a bag of potting mix, pot and plant.
When potting plants, there are a few essential things to be mindful of.
The first is that not all potting mixes are the same, the difference between a good potting mix and a cheap bag of potting mix is chalk and cheese.
A good-quality potting mix has a balanced, stable pH and contains high-quality ingredients including peat moss or coconut coir, perlite, composted pine bark, slow-release fertiliser and wetting agents that support long-term plant health.
They remain light and open, keeping airspace among the particles for healthy root development.
Cheap potting mix often uses soil and low-cost fillers like wood fibre that can compromise plant growth. They compact down easily, become waterlogged, have an unstable pH and can have nitrogen draw down as soil microbes steal nitrogen from plant roots to break down the uncomposed wood fibres.
This results in stunted growth, thin stems and yellow leaves, requiring additional fertiliser and more regular repotting.
Choosing the right sized pot is also important, too small and the plants soon run out of root space, and they also lack the ability to hold enough moisture and fertiliser for good growth.
Too large and the excess surrounding potting mix runs the risk of becoming too wet, as there are no roots to draw on the moisture.
If you need to pot a plant into an oversized container, pay close attention to the plant’s water requirements, watering in and around the root zone only, in the early stages.
To prepare the plant for repotting, gently remove it from the existing container. You may find it easier if you can squeeze the old pot first to loosen it.
Lightly tease out any tightly bound roots, particularly in the lower part of the root ball around the drainage points of the old pot.
It will depend on the type of plant you are potting up as to how brutal you can be with this, but you should try to keep the root damage to a minimum as you go about it.
Trim off any damaged, dead or girdling roots that spiral around the root ball, leaving clean cuts rather than just tearing them off.
When you are ready to place the plant into the new container, start by adding a layer of potting mix in the base of the new pot so that the top of the root ball sits about 20 to 30mm below the rim of the pot.
Holding the plant in the centre of the pot, gently fill potting mix around the root ball, taking care to get it in and around the roots.
Fill the potting mix to the top of the root ball and firm it all down.
Then add a final layer of potting mix to just cover the root ball.
Avoid planting the plant too deep and having potting mix coming too high up the stem, as this can lead to collar rot, which is the rotting away of the cambium layer on the stem.
To help compensate for any roots that were trimmed off or damaged in the potting process, you can give the plant a light prune over.
It is also a chance to build the correct structure in the framework of the plant, so don’t be afraid to prune it harder if required.
This will ensure that the new growth that the plant is about to put on will be in the places we want it.
A small amount of additional slow-release fertiliser can be applied at this stage if you feel that it needs it.
Otherwise, be sure to add some in the weeks to come as the plant begins to grow.
Once you have finished all this, it is critical to water the plant in. By giving the plant a good soak, it will settle the new potting mix around the roots, remove excessive air pockets and help hydrate the plant after the ordeal of the transplanting.
It is a great idea to incorporate Plant Starter in with the water when doing this.
Plant Starter is a root stimulant containing naphthalene acetic acid and indole acetic acid to help encourage new root growth and limit transplant shock.
It is a great product to have on hand whenever you are potting up, transplanting or planting out plants in your garden.
Next time you are in the Garden Centre, and you are not sure about what you need to be doing or how to go about it, be sure to ask the questions.
Because gardeners are always keen to help each other out.