How to grow philadelphus
Often you can smell the delicious scent of Philadelphus (mock orange) before you spy them in a garden. These medium to large shrubs produce masses of white blooms in early summer, and are easy to grow, so why not see if you can make room for one in your garden?
- Heavily scented flowers in early summer
- Medium to large shrubs
- Deciduous, losing their leaves in winter
- Easy to grow in sun or light shade
- Grows well on most soils
- Prune after flowering
- Propagate by cuttings in early summer
All you need to know
What are Philadelphus?
These easy-to-grow shrubs produce clusters of white flowers in early summer. These only last for a few weeks, but usually perfume the air beautifully, creating a lasting impression in early summer.
Choosing the right PhiladelphusThe vast majority of Philadelphus are hardy so can be grown throughout the UK. As a result, the main choices come down to selecting a plant that will be the right size for your garden, as well as choosing a flower form you particularly like. If you go to a nursery or garden centre in early summer, you will often see the plants in bloom, which can be more helpful than looking for pictures in books or online, since you can smell them too!
Eventual sizeThe most important thing is to select a
Gardeners often use the word variety when referring to a specific plant, but the correct botanical term is 'cultivar'. Whichever word you use, it means a distinctive plant or plants, given a specific cultivar name and usually bred to enhance certain characteristics, such as flower or fruit size, colour, flavour or fragrance, plant size, hardiness, disease resistance, etc. Additionally, it is worth knowing that, botanically, variety has another meaning - it refers to a naturally-occurring distinct plant that only has slight differences in its looks. For example, Malva alcea var. fastigiata differs from typical plants by having an upright habit.
- Large cultivars reach around 2.4m (8ft) tall, so are suited to the back of borders, or can be used as a substitute for a small tree in a tiny garden. A popular example is Philadephus ‘Beauclerk’
- Medium-height Philadelphus, for example P. ‘Belle Etoile’, which grows to around 1.5m (5ft), are ideal for planting behind other summer-flowering shrubs such as roses, or growing among tall perennial plants
- Small cultivars with compact and weeping habits include P. ‘Manteau de Hermine’. These are around 75cm (30in) tall and good at the front of a border or in a large container
Flowers and foliageAs far as flower differences go, some are double or have coloured centres, but generally, the overwhelming impression is of a profusion of white blooms. Choose one that appeals most.
If you like coloured foliage, there is the golden form P. coronarius ‘Aureus’ and also a variegated form, P. coronarius ‘Variegatus’.
Bear in mind that after their early summer glory, mock oranges revert to being backdrop plants – green and leafy shrubs – until they shed their leaves in autumn. While they are valuable in the chorus, it’s probably not best to place them in a starring role in your garden, for example as a focal point.
Buying a PhiladelphusThese shrubs can be bought from garden centres and nurseries as container-grown plants. They are normally for sale in 2-litre pots, but larger sizes are sometimes available in garden centres and nurseries, and from online suppliers, with a larger choice available by mail order.
Plants can sometimes be bought
These have been lifted from the ground while dormant, with little or no soil around their roots. Various plants may be available bare root, including fruit trees, hedging plants and some perennials. They are generally cheaper than plants in containers, but are only available in winter/early spring, while dormant
When to plant
- You can plant container-grown plants at any time of year, but they establish best when planted in autumn or spring
- Plant bare-root plants in the dormant season (winter), when the ground is not frozen or waterlogged. Alternatively, pot up into a container to grow on
Where to plantChoose a sunny or semi-shaded site in fertile, well-drained soil.
- Avoid planting golden-leaved forms in full sun as it can damage foliage
- Check on the label for eventual width of the plant, to give plants enough room
- Also check eventual height when considering placement, as some are short and suitable for the front of the border, while a few can grow to the height of a small tree
How to plantPlant container-grown and bare-root Philadelphus as you would any shrub, by digging a hole deep enough to take the rootball, but around twice as wide as the rootball.
Improve the soil that goes back in around the sides of the rootball with well-rotted compost or manure. Water in well and keep moist if you plant in spring or summer. Mulching newly planted shrubs will help retain moisture in the ground.
If you’re unsure, follow our step-by-step guide.
FeedingA general-purpose fertiliser, such as a handful of Growmore per square metre (sq yd), can be applied in spring if your plant needs a boost or the plant is growing on poor soil.
MulchingApplying a mulch of organic matter is a good way to improve soil conditions and add some nutrients. It also keeps weed competition down and preserves moisture in the soil.
Once established, a Philadelphus shrub is unlikely to need watering unless your soil is very free-draining and there is a prolonged period of drought.
Philadelphus don't need deadheading, as they only flower once a year and removing the flowers doesn't improve the next flowering or promote growth in a noticeable way.
Pruning young plantsCut out any dead, diseased or damaged branches after flowering. If there’s a branch that’s crossing through the centre of the plant, you might want to prune that out too – that way you’ll get an open shrub without congestion and branches that rub against each other.
Philadelphus are best pruned after flowering in summer. It’s not vital every year, but it does promote development of new flowering wood.
Pruning established plants
You do this simply by cutting back some of the older growth to new shoots lower down a branch, and by thinning out from the base, removing a few of the older stems entirely (limit yourself to removing one in five each year).
Both greenfly and blackfly can appear in early summer. You may notice these sap feeders when foliage starts to curl in response to their saliva. Interestingly, Philadelphus are one of the winter/spring hosts of the black bean aphid, the blackflies that can cover the tips of your broad beans a little later in the season. They don’t need to be controlled and are usually tolerated.
If you’re a member of the RHS, you can use our online Gardening Advice Service, via MyRHS, for any gardening queries and problems.
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.