Every garden needs different kinds of plants. There are those that form the background and add a little for a long time. I would count hardy geraniums in this category. They gently look after themselves and add some beauty for months. And then there are plants that have a brief, but glorious moment of impact. These include delphiniums, peonies, lilies and lupins.
Philadelphus are in this latter category too. They can be rather uninteresting for most of the year but, when they are in full bloom, they are truly spectacular and their rich, sweet fragrance is so delightful that I could not bear to be without at least one in the garden. Their common name is mock orange because of their wonderful perfume.
Philadelphus are rather old-fashioned garden shrubs and, until recently, the selection was rather limited but there are now many new kinds being introduced that have significant advantages over the older kinds, mostly because they are smaller in habit. And not all are dull in summer with some having variegated foliage. As always, I will be brutally honest in my descriptions so I will deal with the problems first and then describe your options. All are deciduous, losing their leaves in autumn.
Pruning
The biggest problem with philadelphus is pruning. Because they flower in early summer, a very useful period when few other shrubs are in bloom, they do not fit into the pruning regime of spring-flowering shrubs or autumn-flowering shrubs. They should be pruned immediately after flowering. Pruning must be restricted to cutting out a few of the oldest, flowered shoots, near the base. These are then pulled out and any excessively long shoots can be slightly shortened. This is all that should be done.
If you prune in autumn, winter or spring, to radically reduce the size of the plant, it will reduce or prevent flowering. You should not hard prune to try to keep your philadelphus small if you want flowers. And you must never clip them over to make cubes or domes or you will end up with a mass of weak twigs that will flower poorly.
This pruning to restrict size is a major problem because the most widely sold philadelphus is ‘Virginal’. This is a massive plant that quickly reaches 3m high and it will not bloom until these tall stems have produced lots of sideshoots. This will take at least three years after planting. Well before this, most people panic at the sight of strong, vertical stems and hack them back, ensuring the poor thing rarely blooms. The answer is not to plant ‘Virginal’ unless you have plenty of space. Choose the right philadelphus for your site.
Pests
Philadelphus rarely suffer from pests apart from blackfly on the vigorous shoots immediately after pruning. Do not panic. Ladybirds will quickly move in and devour them but you need to keep the faith.
Site
Most philadelphus prefer a sunny spot to bloom well. They are not fussy about soil and will grow on clay and chalky soils but they will not tolerate wet soil, as I have discovered myself after this wet winter and spring.
The choice
Now onto the interesting bit! If the idea of a shrub that flowers for a month and is then dull green is a concern, there are three philadelphus that have coloured leaves.
The most common is Philadelphus coronarius ‘Aureus’. This large (2m) shrub has glorious, zingy lime and lemon leaves. The flowers are small and, like all philadelphus, are white with yellow stamens, and deliciously scented. I have to admit that they are not as showy as some others, against the yellow foliage. There is another issue: like most yellow-leaved shrubs, the leaves can scorch in dry soil in full sun. And in too much shade the leaves become lime rather than lemon. I have mine facing west in a border, partly shaded by a hedge but facing east is also an option, getting sun for half the day. Just avoid a hot, dry, sunny spot.
Even brighter, P. coronarius ‘Variegatus’ (or ‘Bowles Variety’) has large leaves suffused with grey and edged with white. It withstands full sun and flowers well but, of course, the flowers hardly show up at all – but they smell wonderful. It is said that E A Bowles, after whom the plant is named, was allergic to the smell of philadelphus and had his gardeners pick off all the flower buds so he must have thought the leaves were beautiful!
The other variegated kind is ‘Innocence‘ which is a much smaller plant and only reaches about 1.5m. The leaves are dainty and splashed and speckled with yellow. The flowers are quite large and pure white and it is a wonderful, though rather uncommon, shrub.
Avoiding the larger-growing philadelphus for a moment, another you should consider is Philadelphus microphyllus. This is a Mexican plant and unlike the others mentioned so far, it relishes a hot, sunny spot. It is compact, about 1m high and wide, with small leaves, greyish on the back and produces masses of small, dainty flowers that are richly scented of pineapple and orange blossom. It is just the right thing for an urban plot with lavender and buddleias.
‘Belle Etoile‘ is the most popular of all philadelphus and rather unusual because the flowers have a purple stain at the base. It is quite large and will reach 2.4m high and wide but worth the space because of the fragrance and spectacular blooms.
If I had to choose one philadelphus for the garden it would be ‘Manteau d’Hermine’. This is fairly compact, reaching only 1.2m high and has fragrant, double flowers, giving you the look of ‘Virginal’ but on a very manageable plant.
In recent years many new philadelphus have been introduced and most are compact and beautiful. Remember to check the labels before you buy because it is very difficult to restrict the size of a philadelphus without impacting the floral display.
And if you already have one that does not bloom, put the loppers and secateurs away for a couple of years and you will get flowers!
Weekly reminders
Although it is a dull, chilly day, you should complete the planting of your patio pots soon. Add controlled-release fertiliser to the compost before planting to feed your plants all summer.
There is still time to sow some veg, including peas, French beans, lettuce, beetroot and leeks.
Fill gaps in borders with pots of annuals and lilies
Spray roses every two weeks with fungicide to prevent blackspot infecting the foliage and weakening the plants