Why Autumn is the Best Time for Planting

Published on October 10th 2020
A plant, spade and fertilizer in a garden
Autumn is the best time to plant most garden plants. Recently, there's been a shift to planting in the spring, but there are plenty of good reasons why you should be getting your plants in the ground as the leaves turn.

Why is autumn the best time for planting?

In autumn the soil remains warm as air temperatures are drop, encouraging new roots to grow quickly.
By contrast, in spring, the soil is still cold. As a result, roots have to play 'catch-up' as the plant tops shoot up, using up all the plants' reserves before the root system is fully functioning.
Deciduous trees and shrubs - that's those that lose their leaves in autumn - will continue to grow new roots in autumn and early winter, even though those parts above ground have become dormant in preparation for the cold.
Autumn leaves on the ground
Fallen autumn leaves from deciduous trees
In addition to this, garden soils in autumn generally have plenty of moisture. With the inevitable winter rains, this reduces the need for watering, whereas trees and shrubs planted in spring will need regular watering to get them established.
Of course, whether planted in autumn or spring, newly planted items will need adequate watering for a few seasons until they become fully established.

What can be planted in the autumn?

There's one word to sum this up, and that's HARDY! Any hardy plant planted in autumn will be able to get established better.
The list includes shrubs, trees, climbing plants, conifers, fruit trees canes and bushes, roses and of course hedge plants.
If you have a cold garden, then I would caution against planting those plants that are often lumped together as "Mediterranean plants". By this, I mean lavenders, rosemary, thyme and many plants that have grey leaves. These are best planted in spring.
Lavender plants in a garden
Lavenders might be better planted in spring

Autumn is a great time to reorganise

Autumn isn't just the best time for planting. This time of year is also great for reorganising and improving your garden!
This could involve moving plants to a new position. However, remember to move evergreens with as little disturbance to the roots as possible by trying to dig them up with a root ball.
A person digging up a palm tree
Digging a root ball to move evergreen plants
I find that pruning the tops back a little helps plants settle in. This pruning helps the roots catch up with the top growth, as you will inevitably leave some roots behind! This trim goes some way to restoring the all-important root to shoot balance that healthy plants have.

What effect has spring planting had on our gardens?

In short, I believe that spring planting has had a detrimental effect on our gardens.
A shift to buying plants in spring has led to many gardens becoming dominated by spring bloomers, which then lack real seasonal interest during the rest of the year.
Spring buying isn't that surprising, since we are naturally drawn to those things in flower, and retail nurseries and garden centres are full of flowering plants in spring. I should know since I owned one for 35 years!
A few visits during autumn and winter will redress this balance. It will result in a much more exciting garden that is less focused on spring.

Tips on autumn planting

Thorough soil preparation will pay off!
Don't dig a shallow hole - I like to make the hole at least twice the size of the new plant's root ball.
Check that your new plant will be at the same level or just a couple of centimetres below the natural ground level when it is settled in the hole.
Don't leave the top sticking out as that could lead to the roots losing water. I use my spade handle laid across the hole as a guide.
a spade, plant and a hole in a garden
Checking planting depth with a spade handle
Dig the surrounding soil so that your new plant has the best chance to spread its roots.
Break up any compacted sub-soil in the bottom of your hole. Don't bring it up to the surface to avoid mixing it with the topsoil, where all the life is.
Mix some organic matter into the soil that you put back into the hole. This is especially important for soils in poor condition. Use garden compost, recycled composted green waste or even potting compost.
Planting a tall Camellia plant
Back filling the hole with soil, compost and fertilizer
I always add a slow-release fertiliser to the planting hole. I usually use Vitax Q4 fertiliser or Osmocote.
Make sure that the root ball, pot or bare roots are soaked before you even think of planting!
Some autumns can be dry, so it will pay to fill any planting hole to the surface with water. When you've done this, go away and have a cup of tea before returning to plant! The water will have soaked into the surrounding soil.
Backfill with the topsoil fertiliser and organic matter mix.
Firm the backfilled hole with the ball of your foot. Make sure that no voids are left.
Firming a plant in with a boot
Gently firming soil around a bamboo plant
If the soil is very wet, do not overdo firming it up. It might pay to delay until the soil has dried out a bit.
Water your plant to settle it in.
Finally, you might want to consider adding a ring of mulching material of about 5-10 cm deep to trap water in and prevent weeds from competing with your new plant for water and nutrients. Composted bark and garden compost are suitable for this.
For trees, it's good to keep the mulch away from the trunk, as sometimes voles burrow under it and chew the bark off. An un-mulched area of 10-15 cms seems to be enough to prevent this. I guess that they feel threatened by predators if exposed.

Let the fungi help

Virtually all plants have a symbiotic association with beneficial fungi, with no damaging effects.
The mycelium of these mycorrhizal fungi grow over plant roots and connect with them, sharing both water and nutrients. In return, the mycelium receive food from the plant's roots.
These root friendly fungi are now widely available to buy, such as the product Root Grow. It contains root friendly fungi to inoculate the root system and kickstart the natural process.
To apply, simply rub the dry powdered root friendly fungi onto the roots of the new plant.
Rubbing Root Grow onto plant roots
Rubbing root friendly fungi onto plant roots

Plant choice and advice

In autumn the choice of plants to buy is generally much more extensive than at other times of the year.
You may also notice in autumn that garden centre and nursery staff have a bit more time to give you good advice and help you choose wisely!
In spring, staff are often so busy answering everyone's queries, watering, restocking and completing a hundred other tasks that they can only spend limited time with you.
Two ladies buying plants in a garden centre
Gardeners shopping for Clematis
So what are you waiting for, don't waste the opportunity, get planting this autumn! Your plants will be established and growing when everyone else's are still playing 'catch-up'!
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