When is the best time to plant?

This is a question that people ask us all the time: when is the best time to plant plants in your garden? It's confusing for people who aren't experts. There has been a campaign in Ireland for the last few years, every spring, called "It's Garden Time". This campaign is run by Bord Bia, the Irish Food Board and is also associated with "Bloom", the main garden show for the country, held at the start of June each year. "It's Garden Time" is heavily promoted, so it's no wonder that people are a litttle confused. Didn't we always learn that autumn and winter were the ideal planting seasons?

Of course, spring and early summer are lovely times to enjoy the garden, and there is plenty of work to be done then. This is a time for sowing seeds, filling gaps and tidying up. However, the best time to plant is actually at the end of the summer / autumn / early winter. If you think about it, the soil is still warm, the plants are preparing to wind down and there is less pressure on keeping things watered. The days are shorter, the sun is cooler and plants have some time to settle in and establish themselves before they need to reawaken again in spring and start using their roots.

Now that we have plastic pots for most plants (perennials, grasses, shrubs and smaller trees etc) they can be planted throughout the year - except when the ground is frozen solid, which is a rarity in this climate. The only down-side of planting in spring or summer is that you need to water things much more: they're growing, haven't developed any additional roots and are burning through water.  Newly-purchased plants are generally in very good health as they are still 'fresh' from the grower. By and large, newly-planted plants are not going to perish from diseases or pests in their first year. The main cause of their death will be lack of water.

If you do plant in spring or early summer you need to have a couple of things in mind. Do you have a tap and hose nearby? Will you be going away for a prolonged spell when there will be nobody to water? Even in Ireland it doesn't rain all the time! Have you planted properly and in a way that will make life easier for the plants? This would include watering properly after planting and top-dressing the soil with mulch such as garden compost, bark mulch or well-rotted manure. The addition of this layer on top of the soil does all sorts of good things: it stops the sun beating down on the soil and the moisture from evaporating; it rots down slowly and improves the soil structure, making in better and retaining moisture; it maintains the soil at a steadier temperature, ie cooler in summer and warmer in winter; and it keeps down weeds.

Some plants are only available at particular times of the year. Bare root trees and shrubs are just as they sound; they are grown outdoors, in the ground, and are then dug up without soil on the roots. This can only happen in the dormant season - between late autumn and late winter. Root-balled plants are grown outdoors in the ground. They are dug up with a 'ball' of soil around the roots and are then wrapped in hessian. Larger specimens also have their roots held together in a wire cage. These plants - normally larger specimen trees and shrubs - can only be dug in the dormant season, although they can be planted all the way into the summer. However, it's best if they are planted as soon after digging as possible, as this will allow them to settle in without watering for several months.

Below is a timetable of what can be planted when in the Irish climate:

  • Bare root trees and shrubs: These plants should be planted during the 'dormant season' which is between approximately November to March. This is an inexpansive and convenient way to plant woody plants and is ideally suited to hedges and forestry. Because these plants are sometimes in short supply, it's generally ideal to order and plant them before the new year rather than after it. Growers and suppliers can run out of stock in the new year and heading towards March.
  • Root-ball plants and mature specim trees and shrubs: These plants, generally larger than bare root plants, are also best planted the 'dormant season'. Because there is soil attached to teh roots, they do not dry out as quickly after being dug from the ground and they can be planted when i leaf in the growing season. However, this puts pressure on them as they have a greater requirement for water by this stage. Ideally, they should be ordered, dug and planted in the dormant season. As supply can be limited, it's a good idea to at least have these plants ordered adn booked before the new year.
  • Container-grown trees and shrubs: Container grown trees and shrubs range in size from smaller plants available in the garden centre to very mature specimens available form nurseries and suppliers. These plants have the advantage of being available all year round. If planted during the growing seasoon (April to October) extra care needs to be taken to keep them watered.
  • Container-grown perennials, grasses, ferns etc: A hundred years ago, before we had cheap plastic flowerpots, these plants would have been supplied either bare root or with a root ball attached - ie as divisions of larger existing plants. This can only happen during the dormant season. As it happens, this is probably still the best time for planting perennials etc as they haev plenty of time to settle in without the need for water. However, the convenience of plastic pots means they can be planted all year round, and it can be immensely satifying to turn an empty bed to one in full-bloom withing a couple of hours. Take the advice above if planting during tehvgrowing season: water and mulch well.
  • Bulbs: Bulbs are generally planted one or two seasons before they flower. Therefore, spring-flowering bulbs are planted in the autumn and early winter. Summer-flowering bulbs are planted in spring. There are a couple of exceptions to this rule: autumn-flowering crocusses (Colchicum) are planted in winter as they actually grow and send up leaves in the spring and then flower without leaves in late summer. Also, some bulbs can be planted 'in the green' (ie in leaf) as small plants in containers. This is frequently the case with Snowdrops (Galanthus) as some horticulturists argue that they take off better when planted first into pots and then into the ground.
  • Bamboos: Bamboos are generally cultivated in the following way. They are grown in the ground in specialist nurseries. Clumps are divided up and small sections are potted on into plastic pots. These pots are grown on for about a year and the plants are frequently potted on one or more time into larger pots. The end result is a healthy, established plant with a well-developed root system in a plastic pot. These plants can be planted at any time of the year. However, the same caution should be applied if planting bamboos during the summer as they are very 'thirsty' plants after planting. The large leaf-surface means they can dry out quickly. It's more important with bamboos than with almost any other plant to ensure that they are well watered and mulched, whatever time of year they are planted. If an ideal time for bamboo planting had to be given, I would suggest autumn and the first half of winter.
  • Lawns: Lawns (ie grass seed) is best sown at two times of the year: spring and autumn. September is generally considered the best month, when the ground is still warm, moisture or rain is more abundant and there is a long spell without onerous competition from weeds. The second best period is in mid-spring when it's starting to warm up. Generally, however, Ireland is a favourable climate for sowing grass seed and grass grows easily and fast.

 Useful planting tips and advice: