Example of a root bound plant (above and below).
Note how the roots have grown out of the
bottom of the pot and are circling around the pot.
Teasing out the roots
Ready for planting - dig the hole to the right size
Add water to the well around the plant
Planting correctly will not only get your garden off to a flying start, but it will also ensure that your plants' root systems develop as healthily as possible, maximising their long-term stability. The ideal method depends on the type of plant you are putting in and to some extent the purpose of the planting.
Choosing the right plant
A common mistake made by gardeners is in assuming that large potted plants will always be the quickest way to fill a gap in the garden. There is a lot of evidence that small plants (often known as tubestock) will rapidly overtake much larger plants of the same species that have come from bigger pots. The explanation for this is that large plants are often rootbound in their containers (i.e. their roots have become twisted and kinked and this leads to a weaker root system overall). The bottom line is that smaller plants, say 10-15 cm tall, are a very viable alternative for rapid establishment of new plantings.
When looking for planting stock of trees and shrubs particularly, always check the drainage holes at the bottom of the pot. If there are lots of roots trying to escape then the plant is highly likely to have permanent damage to the root system and it is best avoided. If in doubt ask a sales person at the nursery to remove the plant from the pot and show you the root system. Avoid plants that have roots curling in a circular fashion around the base of the pot.
Considerable damage can occur to the root system of a plant that has been kept in a pot that is too small. The roots curl around the bottom of the pot and continue to do so long after they have been planted in the ground. As the plant grows, the root system slowly but surely strangles itself, and the top of the plant gets too big for the struggling root system. Usually this results plants blowing over in storms.
The following steps should work for any type of plant:
1. When preparing the planting hole, ensure that it is significantly wider than the root ball of the plant going into it. Loosen the soil in the base of the hole and in the pile of topsoil you will use to backfill around the sides of the root ball. You can mix in an appropriate compost, as well as a suitable quantity of fertiliser (follow the directions on the pack). The clay breaking substance gypsum can also be a good addition to the bottom of the planting hole if you have clay that sets hard like concrete when it is exposed to the sun. A large handful of gypsum should be sprinkled over the clay at the bottom of your planting hole and mixed in with a garden fork. If you know the soil in your hole is also acidic (courtesy of a pH test or local knowledge) then you could also use a handful of lime (unless you are growing acid-loving plants such as azaleas, camellias and some natives).
2. When you are digging your hole always test the depth by placing the plant into it while it is still in its pot. If the hole is too big or small it is then a very simple matter to remove the plant while you adjust the depth.
3. Carefully remove any weeds that may have invaded the pot.
4. Immerse the whole pot in a bucket of water until bubbles have stopped rising from the potting mix. This is one of the best tips for ensuring that your plant does not die of moisture stress in the first few weeks, particularly in very hot weather.
5. If there are any roots curling around the bottom of the pot when you remove the plant, don’t be afraid to tease the roots out and cut away any that are badly curled. And resolve never again to patronise the retailer that sold it to you unless you can inspect or be shown plants’ roots to make sure they are not pot-bound.
6. Place the plant into the hole and backfill with the topsoil ‘cocktail’ you have already prepared.
7. Create a 'well' around the plant that will hold water there while it soaks into the soil.
8. Mulch around the plant but leave a gap of five to ten centimetres around the stem to minimise the potential for collar rot.
9. Water the plant to remove any air pockets around the roots. Stimulating faster root growth can give an extra boost to important plantings. Root promoting substances such as the various seaweed based products are based on a group of plant hormones that stimulates root formation in plants generally and cuttings in particular. The effect is the same on new plantings in the garden; simply use a watering can to spread it around them at recommended rates.
Frequently asked questions about planting
What if you do end up with a pot bound plant?
Most plants will cope with some judicious root pruning that will give them a chance of regenerating a new, unrestricted root system. The first step is to find where the roots start to curl and cut off the offending coil. Also gently tease the root system out of the mould that the pot has created. At the end of this process the roots will be pointing outwards from the root ball rather than inwards in a circle.
Should I put compost in planting holes?
The standard advice for planting in most gardening literature is to dig a hole that is much deeper than the root ball of the plant you are putting in. The advice usually goes on to recommend a generous application of compost that is dug into the soil at the bottom of the hole. Advice from professional landscapers is now suggesting that this approach can cause serious problems, especially in poorly drained soils.
We can get a clue by looking at how Mother Nature applies organic matter to soils. Leaves, manure and other organic materials fall on the soil surface and form what is known as an organic horizon that slowly breaks down to nourish plants and build up topsoil. Thus it is rather unnatural to dump a whole lot of organic matter into the bottom of a hole. This practice can lead to a couple of problems. Firstly the composting process may continue if the compost is not ‘mature’ – this will rob the soil of nutrients and valuable oxygen, needed by the roots for respiration. Secondly if the organic matter continues to decay it will decrease in volume and cause the plant to sink in the planting hole. If the soil is poorly drained the plant will effectively be sitting in a sump with its roots constantly sodden – a recipe for root rot.
Should I stake my new plant?
If you use smaller plants (tubestock) that are around 10 and 15 cm tall then there is much less need for staking if at all. It is best to do without a stake if the plant is quite stable after planting – this is the normal situation in natural situations after all. An unstaked plant blows around in the wind and this stimulates the plant to strengthen its stem naturally. If, however the plant is a little floppy then a small bamboo stake (or similar) is all that is required. Use a tie such as an old stocking that has some flexibility and leave the plant with a little room to move after it is tied up. Once the plant has started to grow and is stable in the ground the stake should be removed. When planting taller specimens from pots, the bigger they get the greater will be the chance they will be ‘top heavy’, and rootbound leading them to blow over even if they do establish. So staking these large plants is essential until their roots start to establish in the surrounding soil.
What is the best way to water my new plant?
A handy way to water new plantings is with a 2 litre plastic drink bottle. Remove the cap and cut the base of the bottle off as close as possible to the bottom. Then upend the bottle and bury the neck beside your newly planted tree or shrub. The bottle can then be filled with a hose every few days and the water will slowly permeate into the root zone. Solutions of liquid fertilisers can also be applied in this way. The excellent growth, as well as the savings on your water bill that result from using this method, will pleasantly surprise you.
What is the best material to mulch my new plant with?
Mulches come in many shapes and sizes and are undoubtedly very beneficial for saving water and increasing establishment and growth of new plantings. There is a basic question to ask when selecting mulch. Is it composted or not? Mulches such as pine bark and sawdust are normally composted before use (you can tell by their very dark brown or black colour) will be best used where a gardener is trying to build up organic matter to improve the soil such as in vegetable gardens and flowerbeds. For more extensive areas where water conservation is more of an issue, uncomposted materials such as wood chip or straw will provide mulch that lasts much longer as it composts very, very slowly. This can be an advantage in larger scale plantings such as driveways.
About the author
Angus Stewart is the author of several horticutural books including "Creating an Australian Garden". Angus also appears regularly on Australian television and radio shows. Angus's website is called "Gardening with Angus".