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What to plant in September in Dublin
Seasonal Gardening
What to plant in September in Dublin
September can be one of the most useful planting months in Dublin. The soil is often still warm from summer, while cooler days can make it easier for new plants to settle in.
Is September a good month for planting?
That does not mean every plant should go into the ground immediately, or that autumn rain will do all the watering for you. Good September planting still depends on four things: light, drainage, wind and available space.
Yes, provided the ground is workable and you can keep an eye on moisture while new roots establish.
Warm soil can support root growth, and plants usually face less heat stress than they would in midsummer. This can make early autumn a good time to plant hardy trees, shrubs and perennials.
Conditions still vary from garden to garden. One Dublin border may be sheltered and free-draining, while another stays wet, exposed or shaded for much of the day.
Before planting, check:
- Light How much light the area receives
- Drainage Whether water drains away or sits in the soil
- Exposure How exposed the position is to wind
- Mature size How large the plant will eventually become
Trees and shrubs to plant in September
Container-grown trees and shrubs can be planted in September when the soil is moist but not waterlogged.
When to wait
- The soil is waterlogged
- The weather is unusually hot and dry
- You cannot water regularly during establishment
- The plant is tender or unsuitable for the exposure
- You have not allowed enough space for its mature size
Hardy perennials for borders
September is also a useful time to plant many hardy perennials.
The soil can still be warm enough for roots to begin establishing, while cooler conditions reduce the pressure on newly planted foliage. Perennials planted now can settle before winter and begin growing again when conditions improve in spring.
Choose plants according to the border rather than simply choosing what is flowering on the day.
Trees and shrubs to consider
- Deciduous shrubs
- Hardy evergreen shrubs
- Container-grown hedging
- Small ornamental trees
- Container-grown fruit trees
What to consider for perennials
- Full sun, partial shade or deep shade
- Moist or free-draining soil
- Shelter or strong wind
- Eventual height and spread
- Whether the plant tolerates winter wet
Spring bulbs to plant now
September is an important month for planting many spring-flowering bulbs.
Bulbs to plant in September
- Daffodils
- Crocuses
- Hyacinths
- Suitable alliums
For containers:
- Use pots with clear drainage holes
- Avoid leaving containers standing in water
- Use a suitable, free-draining compost
- Check occasionally that the compost has not become completely dry
Hardy annuals to sow in September
- Cornflowers
- Pot marigolds
- Poppies
- Larkspur
- Ammi
- Poached egg plant
Biennials to plant out
- Pansies
- Honesty
- Foxgloves
- Wallflowers
- Verbascums
Vegetables and salads for September
- Spinach
- Winter lettuce
- Rocket
- Salad leaves
- Radishes
- Overwintering onion sets
- Spring cabbage plants raised earlier
For the best chance of success:
- Sow earlier rather than later in the month
- Choose a sheltered, well-drained position
- Keep seedbeds evenly moist during germination
- Protect young plants from slugs, pigeons and harsh weather where needed
- Avoid sowing into cold, saturated ground
What still needs watering in September?
- Newly planted trees and shrubs
- Hedges planted in recent months
- New perennials
- Plants added during summer
- Containers and hanging baskets
- Plants beneath walls, eaves or dense tree cover
- New seedbeds
- Large-leaved plants in exposed positions
How to check whether a plant needs water
- Water thoroughly after planting
- Check the soil regularly during dry or windy weather
- Water more slowly on compacted ground so it can soak in
- Check containers more often than borders
- Keep grass and weeds away from newly planted trees and shrubs
- Do not add more water when the soil is already saturated
Do established plants still need watering?
- Trees and shrubs planted this year
- Recently planted hedges
- Large container plants
- Fruit and vegetables still producing
- Plants in rain shadows
- Anything showing wilting, dry leaf edges or early leaf drop
Four checks before planting in a Dublin garden
- Light Work out how many hours of direct sun the space receives. A bright-looking wall is not necessarily a full-sun position. Watch the area at different points during the day where possible.
- Drainage After heavy rain, does water disappear or remain on the surface? If the ground stays wet, choose plants that tolerate those conditions or improve the planting area before adding plants that need free drainage.
- Wind Open, elevated and coastal gardens may need tougher plants than sheltered urban spaces. Wind also increases moisture loss, so newly planted specimens may need more frequent checking.
- Mature space Check the eventual height and spread, not just the size of the plant in its pot. Leave enough room from paths, windows, boundaries and neighbouring plants. Moving a shrub later is possible, but it is not usually anyone’s preferred Saturday.
Common September planting mistakes
- Assuming autumn rain will handle the watering Rainfall can be patchy, and it may not penetrate deeply enough to reach new roots.
- Planting in waterlogged soil Roots need air as well as water. Saturated soil can slow establishment and cause root damage.
- Planting tulips too early Daffodils and crocuses can usually be planted in September, but tulips are generally better left until later in autumn.
- Ignoring mature size The supplied plant is only the starting point. Check what it is expected to become.
- Filling every empty space A gap is easier to live with than a large, unsuitable shrub planted 30 cm from a path.
- Watering by calendar Check the soil. The weather, plant, container and garden conditions all affect how often watering is needed.
Plant now, wait or reconsider?
September planting is not about putting as much as possible into the garden. It is about using the season well and giving each plant a sensible start.
Plant now when:
- The soil is workable
- Drainage is suitable
- The plant matches the position
- You can water while it establishes
Wait when:
- The soil is saturated
- The weather is unusually hot or dry
- You cannot provide establishment care
- The planting area is not prepared
Reconsider and choose another plant when:
- The mature size is too large
- The site is too exposed
- The soil stays wetter or drier than the plant prefers
- The available light is unsuitable
September planting checklist
- Check light, drainage, wind and space
- Confirm the plant’s mature size
- Prepare the soil and remove weeds
- Water the plant before taking it out of its pot if the root ball is dry
- Plant at the correct depth
- Water thoroughly after planting
- Check moisture regularly during establishment
- Avoid planting into saturated ground
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