PIERIS FORMOSA VAR. FORRESTII
Article by David Marks
Pieris formosa var. forrestii are delightful small to medium sized trees with stunning white flowers which are produced in May. In March and April the new leaves are produced in a vibrant shade of light red.
If you can provide the correct conditions (explained in detail below) they are trouble free trees and there is a variety for even a small garden.
This is an easy and trouble-free tree to grow but there are a few points to be aware of. Use the list below to decide if this is the correct tree for you and your garden.
- This is an evergreen small tree. For most of the year the leaves are green but from March to May the new leaves are a beautiful shade of light red.
- It reaches full size after about 15 years, this a slow growing tree. Expect a maximum height of between 2.5m (8ft) to 4m (13ft) depending on the variety. Spread varies between 1.2m (4ft) to 2.5m (8ft).
- It produces a magnificent display of white flowers in mid May to early June which lasts three weeks. See the pictures below for an idea of what to expect. The flowers have a slight vanilla scent and attract bees.
- The leaves and the nectar of Pieris are poisonous to humans and animals if eaten. Less well known is that if the nectar of Pieris flowers is collected by bees, the honey produced is also poisonous.See the section near the end of this article about the extent of the danger. This is often wildly exaggerated.
- Pieris prefer slightly acidic soil and will not grow successfully on alkaline soils. Loam and sandy soils are fine but heavy clay soils are best avoided. The ground should be moist but not waterlogged, avoid very dry ground.
- They will grow in sun to partial shade will but grow best in dappled shade. Especially avoid full sun in the morning which may well damage the emerging new leaves.
- Hardy and will withstand temperatures down to -15°C. However, a combination of strong winds and frost can cause significant damage at higher temperatures. Pieris need to be planted in a sheltered position
- Aside from a mulch in May, these trees does not require any attention after the become established. Do not feed unless your soil is very poor in nutrients, especially not with a general nitrogen fertiliser.
Pieris formosa var. forrestii ‘Wakehurst’
VARIETIES OF PIERIS FORMOSA VAR. FORRESTII
There are two varieties of Pieris formosa commonly available in the UK. Each is described below in order of popularity. Other varieties are very similar.
PIERIS FORMOSA VAR FORRESTII ‘WAKEHURST’
Shortlisted for the Plant of the Centenary in 2013, this is probably the most popular Pieris variety in the UK. It has been awarded the RHS Award of Garden Merit.
Taking about 10 years to reach full size, height will be 4m / 13 feet and 2.5m / 8 feet wide. It will only grow well in acidic ground. It prefers dappled shade in damp, well drained ground.
The leaf shoots are produced in March to April and can be damaged by frost. Full exposure to early morning sun increases the risk of frost damage. It grows best in a sheltered position.
The leaves first appear in late March and are initially a dark red. They then turn pink, then almost white and finally medium green in mid May.
The white flowers appear in May lasting into June.
PIERIS FORMOSA VAR FORRESTII
Very similar to the ‘Wakehurst’ variety above. The principal difference is that it grows to a slightly larger final size – 5m / 16 feet high with a spread of 3m / 10 feet. This variety does not have an RHS AGM.
The plant was first introduced to the UK in 1905. The plantsman Mr. Forrest harvested seeds from plants growing in Yunnan (South West China) and cultivated them in the UK.
Ness Botanic Gardens in Liverpool claim they have the original Pieris Formosa Var. Forrestii from which all those now growing in the UK originate, including the ‘Wakehurst’ variety.
Planting a Pieris tree is no different most other small trees. But before you plant it check that it will have sufficient room to grow to its eventual maximum height of 5 metres / 16ft and a spread of 3m / 10ft. The best time to plant a Pieris is in early autumn.
The position of the tree is key to its future. Choose an acidic soil, dappled shade with no full sun in the early morning. The area should be moist but well-drained.
As a rule of thumb and to be on the safe side, plant your tree at twice its eventual height from any buildings to avoid damage. Dig a hole twice the width of the existing roots and set it into the hole to the same depth as it was in the container. Gently firm the soil around the roots and water well. Sprinkle a couple of handfuls of blood, fish and bone into the surrounding soil and work in gently with a trowel.
Your Pieris tree is unlikely to need any pruning throughout its life but if it does, the best time is in early summer soon after the flowers die down. This will maximise the number of flowers produced the next year.
According to the book ‘Poisonous Plants: a guide for parents and childcare providers’ by (author Elizabeth Dauncey) there is an average of 2 people killed in the UK by all plant poisoning. The plants most likely to be among those two each year are hemlock (not widely sold) and yew. Although eating any part of a Pieris tree can cause very unpleasant side-effects, the risks of death are minimal.
Compare that that to the estimated 6 children who were killed in bicycle accidents in 2015 (ROSPA) and it’s clear that there are far more dangerous things in life than Pieris trees.
PESTS AND DISEASES OF PIERIS
Pieris are strong growing plants and are rarely attacked by pests. Sometimes, but not often, they can suffer from leaf spot (see below).
Where problems are encountered with Pieris it is most frequently environmental. They need acidic soil, moist but not waterlogged and thrive in dappled shade.
The symptoms of this problem are dark spots on the leaves. Affected leaves eventually fall off and in bad cases the plant can be severely affected. The latest research indicates that in most cases the damage is caused by damp, humid and / or cold conditions rather than disease.
Where the plant is only partially affected the solution is to remove spotted leaves and burn them as soon as they are noticed. Where the damage is more severe you may need to accept that the position of your Pieris plants is just too damp.