Gareth Carter: Shade trees to provide shelter from scorching summer sun

The silk tree (Albizia julibrissin) has distinctive soft, ferny foliage that lends itself to providing a good dappled shade from its naturally spreading branches. Photo / Supplied

As I write this I am reflecting on the excellent rainfall last weekend. Rain in February is a great gift for gardeners and farmers.

While the deluge was intense, it has really refreshed gardens, lawns and water tanks, and will have lasting effects into autumn.

The heat returned quickly after, and it is during the heat of summer that the value of shade trees is recognised. In a carpark, the spot under a tree becomes the favoured park for the car. At places like Bason Botanic Gardens or Virginia Lake, under a tree is the favoured picnicking spot.

Around the home, a tree can be planted and grown on the north and western aspects to shade the house during summer, providing a cooling effect and reducing the need for heat-pump cooling, or simply reducing discomfort from an overheated house. If a deciduous tree is chosen the leaves will drop in autumn, providing welcome winter sun into those same areas.

If you have ever thought a shade tree in the backyard would be nice then it's probably during the hot summer days like we are having now. A tree to dapple the strong sunshine, to provide some relief from the heat, a tree to sit under and read a book or for the kids to play under without getting sunburned.

You know that a shade sail could provide the same sun protection, but it does have not the same cooling effect as a tree. The mass of water stored in a tree that travels from the soil into the roots through the trunk and branches then evaporates out the leaves, provides a cooling effect that is unsurpassed.

In situations where you need the tree to also provide privacy from neighbours or remove an object from view, an evergreen may be a better choice.

There is a great selection of trees that will provide excellent shade. The skill is to choose one that will meet the needs and requirements you want from it. Things to consider are what size you would like, what space is available, would you like it to flower and would you like something with good autumn foliage colour for seasonal interest. These need to combine with the practical implications such as soil type, exposure to wind, frost, cold, coastal salt spray etc, to ensure the tree's successful growth.

For a smaller town section, consideration needs to be given to the shade a tree may create for a neighbour, so smaller-growing trees or those that respond well to pruning will make a better choice.

Cercis Forest Pansy is a stunning smaller-growing deciduous tree suitable for many town gardens. Popular for its deep-burgundy foliage colour, Forest Pansy can be kept tidily to about 3m tall and 3m wide, providing a wonderful shade tree for a small courtyard situation. If left untrimmed, Forest Pansy will grow to about 5m.

Flowering cherries (Prunus) are a very popular choice of shade tree. There are several varieties that all have slightly different growth habits. This means if it's a flowering cherry you want, then you can usually find one that will grow to the size you have available.

Kanzan is a taller-growing variety with spectacular double pink flowers and forms a vase-shaped head, while Pink Perfection has a very similar flower but its growth habit is far more spreading so it forms a better shade tree if it's width you need. Jim's Delight is a relatively new release and reaches only 3m high. A real little gem if you want a small shade tree for a tight corner, it has spectacular single pink blossom in the early spring as well as spectacular autumn foliage as the leaves turn shades of red and orange.

Flowering cherries are a popular choice for a shade tree. Photo / NZME

A top-selling flowering cherry tree is Shimidsu Sakura. This has an excellent spreading umbrella-shaped growth habit. It will grow about 4m high by 5m wide and, as well as being an excellent shade tree for the summer, it puts on a spectacular show in October with deep-pink buds opening to double white flowers toned pink. Shimidsu Sakura also has a good display of autumn colours with leaves turning tones of orange and yellow before dropping.

Another excellent shade tree is the silk tree (Albizia julibrissin). In flower at the moment, you will be able to spot them around the city with their mass of fluffy pinky-red flowers covering the trees. Hotter summers seem to improve the flowering of these trees. The silk trees have distinctive soft ferny foliage that lends itself to provide good dappled shade from its naturally spreading branches. These trees, if left to grow, will reach about 6m tall and 5m wide but are easily pruned to a much smaller size. They grow quickly so good shade can be established in three to four years.

Driving around the city I have also seen some magnificent jacaranda in flower with their cool bluey-purple blooms. These, too, can be kept smaller with pruning.

Fruit trees can also make good shade trees. A plum tree at the bottom of the garden can make an excellent shade tree, with a mass of white blossom in the springtime and then an abundant crop of fruit around Christmas. The added bonus is the fast growth rate of plum trees from which shade can be established as well as being able to prune them to size. So why not make your shade tree productive and choose a plum or another fruit tree?

Other fruit trees that make good shade trees are cherry trees. We have already talked about the beauty and good growth habits of flowering cherries but you can also consider a fruiting cherry. The blossom isn't as spectacular but the bonus of growing your own cherries is an option worth weighing up.

Evergreen shade trees tend not to change through the seasons and, apart from flowers and sometimes berries, they will offer a very similar look year round. If you want to use your shade tree as a year-round screen to offer privacy then an evergreen tree will be a better option for you. A lot of the larger-growing native trees, such as the puriri, karaka, pohutukawa and titoki, make spectacular shade trees but in a town section these will usually grow too big for the space available.

There are some good evergreen trees for smaller and town sections. Leptospermum Copper Sheen forms a good shade tree when its lower limbs are pruned. It has a lovely weeping habit with its coppery-burgundy red foliage making it an attractive tree. It also becomes covered in a mass of white flowers in summer. Being very fast growing makes it a good option for quickly establishing privacy. It responds well to trimming and can also be grown as a hedge.

Some michelia varieties form lovely shade trees. I say some, because there are varieties that simply don't grow large enough and their habit is shrubby. However, the dolstopa variety and its hybrids form good evergreen trees. These varieties will form a trunk with a rounded head of branches and foliage that will offer good shade from the hot summer sun. A real feature of michelia is an amazing display of highly fragrant, white flowers in late winter and early spring.

So if you are feeling the summer heat, consider a good spot to plant a suitable shade tree.

• Gareth Carter is general manager of Springvale Garden Centre.