It is traditionally said that on 25 November, Saint Catherine’s day everything that is planted will take root and grow !
Effectively the earlier a plant is planted in the season the quicker its roots will develop and therefore its growth will be better in the first year.
If you forget to plant on this date, bear in mind that plants will always benefit in terms of growth from being planted today rather than tomorrow. The best period for planting is really when you are ready to plant, when you have the time and the desire to plant and follow a few basic rules. In this case do not hesitate to give the plants additional water during their first year (see the chapter on How to water properly).
Generally speaking it is best to plant when the climatic conditions are favourable.
In the mountains, planting usually takes place early, either in September or October or in the spring once the snow has melted.
If you chose plants that are not particularly hardy for you region it is best to plant them in the spring so that they avoid the very cold spells. This is especially true for evergreen plants and when plants are young.
Balled or container grown plants
Unlike plants with bare roots, these plants suffer very little stress when they are planted. They can therefore be planted throughout most of the year.
However planting should be avoided when the ground is unworkable; such as in winter when the ground is frozen, or during a very dry period when the soil is rock hard.
Truffle favouring plants
The planting period for these balled plants is basically the same as those described above. However it is best to avoid planting between June and August as the lack of water may damage the mycorrhiza. A drip watering system would help narrow down this period.
Bare rooted plants (without soil or root ball)
Bare rooted plants suffer high levels of stress when planted. They are therefore best planted when the plant is dormant, autumn is the ideal period.
For plants that are deciduous, this period starts as soon as all their leaves have fallen and stops as soon as the buds begin. For evergreen plants their planting period is even more restrictive as they never have a real dormant period.
There are basically two periods for planting bulbs.
Spring flowering bulbs (crocus, tulip, hyacinth...) are planted in the autumn from September through to the beginning of December. This gives them the whole of the winter to settle in and be ready to start growing when the first rays of sunshine arrive in the spring.
Summer flowering bulbs (canna, dahlia, lily...) are best planted in the spring. If they are planted in the autumn they can be damaged by the winter frosts and this would have a harmful effect on their subsequent flowering.