It is so lovely to have a tree in close proximity and even if you don’t have a massive garden, it is possible to grow a tree in a planter box. The most important aspect of a tree planter is that it must be deep enough to allow the trunk to stretch and grow as it’s nourished by the soil.
Another factor is whether your tree will be grown indoors in a centrally heated environment or if it is located outside. You may be planning to have a planter box on roller wheels, which can be placed in a protected environment during a harsh winter.
Read on to discover how to keep a planter box tree happy and healthy for many years to come.
What materials can I use for my tree planter box?
Terracotta clay planter boxes
Terracotta clay planter boxes are a great choice for trees. As clay is porous, it creates an ideal environment for tree roots. The only downside is its weight so if this is to be placed on a balcony, think about the combined weight of the planter, tree and soil before you buy one.
Wood is an excellent natural material for planter boxes but it will need to be regularly maintained and possibly lined as well. Pine, larch, cypress and oak all offer individual characteristics and you may want to take your time choosing one you like. You can also visit your local wood supplier and take advice from them about durability and sustainability.
Aluminium and galvanised steel
Metals like aluminium and galvanised steel are also suitable for a tree planter and their durability ensures elegance for many years to come. Some are scratch-resistant too which is practical in a busy family garden. Make sure you choose a rust-resistant metal planter box or you may have to replace your planter sooner than you think.
Composite planter boxes
Composite planter boxes are constructed from recycled materials and they offer more flexibility in terms of shape and colour than more traditional materials. They are also lightweight and within most people’s price range. Some of these also have LED lighting incorporated into them so your tree planter box can be a light source at night. However, as darkness approaches, trees photosynthesise the light their leaves have absorbed during the day, so nocturnal lighting may not suit the tree you choose. Try to make sure the lighting is aimed at the ground not upwards – this will help.
Glazed ceramic planter boxes
Glazed ceramic planter boxes for trees look really attractive but if weight is an issue, for example on a patio or balcony then check before you buy. This type of material is heavy which is steady for a growing tree but if you have to move this pot, you may need help and/or a roller system. These can be more expensive than composite plastic tree planter boxes so if cost is an issue, maybe consider a different option.
Brick is another possibility for a tree planter box and will offer solid support for a growing tree. However, it is very permanent so consider well where you build one.
Once you have chosen your material, let’s get started! There are some plans for building your own planter box (and greenhouse!) available here.
Read on for suggestions for the best trees to plant in a planter box below but first, let’s consider what conditions your chosen tree will need for good growth. It’s also important to think about where you will sit to view this tree.
If it’s outdoors will you sit on some decking or in a courtyard to look at it? Is it sheltered there? The tree will go through every season in this planter box and some trees offer year-round interest, whilst others are famous for their glorious spring blossoms.
Position your planter box where you can view it all year round, you don’t want to miss the gorgeous autumn foliage that many trees will offer. Before you plant your tree, place it in a bucket of warm water and allow the roots to spread.
Gently, ease any roots into a natural shape if they have become pot-bound and let them sit happily in the water while you read the rest of this article.
What factors should I consider for my tree planter box?
Height and spread of the tree
When you buy a small tree, calculate how tall it is going to grow and ensure that the location will allow it enough space to grow. The planter box should be calculated to be twice the depth and width of the root ball of the tree you choose.
You also need to allow for future growth so make sure the height of the box allows for this by adding an extra 30cm (1 foot) for approximately 4 feet of trunk growth.
Next look at how far the tree will grow in width and then decide if there is enough space for the tree to be comfortable. If it is in a conservatory, how tall is the roof? Will it be shaded by other plants? Is there direct sunlight? If it is outdoors, does it need protection from winter frost and snow?
I’ve been surprised by a grapefruit seed I planted which grew tall enough indoors to become my Christmas tree, so consider this one carefully!
The sturdiness of your planter box
You will be adding a living plant to your planter box so remember that it needs to be sturdy. No tree will thank you for falling over every time somebody bumps into it.
Choosing a heavy planter will help but if it is a composite or lightweight planter, make sure you add some large stones or bricks to the bottom to help balance the tree. Any broken crockery will also help to add weight and assist with drainage.
Some trees will need manure and lots of rich soil. Soil is heavy which helps to secure the tree in place but a huge planter box will require a lot of soil!
You can fill up your planter box by adding weighty items at the bottom and then consider adding pebbles and some sand to aid drainage. Any garden topsoil you have available will help too, then place your tree in the planter box carefully. Fill all around the root ball top with compost, either homemade or bought. Then water the tree thoroughly and allow the soil to settle.
Trees will have different watering needs but all of them need some water. All will like good drainage, which can be achieved by adding either a layer of charcoal or some pebbles. Self-watering systems are one option but visiting your tree every few days to check is a pleasurable activity so enjoy it.
Check which type of light your tree prefers. If full sunshine is needed, you can position the planter box near a south-facing wall, enabling it to retain heat for longer.
If you buy a shade-loving tree, then find a spot where the afternoon sun is shaded by a building or another tree so that your tree benefits from cooler afternoon light. Check the label carefully and then choose a spot that suits the growing needs of your chosen tree.
This is an important question that determines if your tree will be placed in an interior or exterior planter box. Cherry trees don’t mind a bit of frost and snow whereas a citrus tree, like lemon or lime, will die if it snows. So let’s take a look at the types of trees recommended for a planter box:
Types of trees that can be grown in a planter box
- Bay is a tree whose leaves are used in cooking, it’s happy in a pot but it can grow as tall as 23 feet (7.5 m).
- Flowering trees like cherry and magnolia are hardy and offer gorgeous foliage during one season. Their size will depend on the size of the planter they grow in.
- Hardy fruit trees such as cherry, pear and apple grow well in containers. Try to make sure they are grafted on dwarf rootstock which limits their eventual height.
- Citrus trees, like lime and lemon, are fine in planter boxes but must have some winter protection. Their scent is heavenly when in bloom and the fruit is excellent too.
- Colourful trees like red maple and Japanese maple grow well inside or out but may need some protection from winter weather.
- Yucca is regarded as a hardy shrub but it can grow to over 10 feet when in flower and its striking foliage is fabulous in a container planter box.
- Decorative leaves such as Salix integra – the dappled willow, are beautiful in a planter box.
- Nut trees with flowers, foliage and fruit like the cobnut hazel tree are a delight in every season. Yellow catkins in spring are followed by lush green foliage which turns to scarlet red in autumn, followed by a harvest of nuts. Buy one on dwarf rootstock to keep it to a manageable height or you will be pruning vigorously every year.
- Palm trees can be bought as dwarf varieties and offer calming foliage in any environment. Some varieties need to be indoors.
- Trees such as lilac and buddleia, loved by pollinators for their amazing scent, are great for anybody who loves watching bees and butterflies.
- Eucalyptus offers a delightful scent all year round and it’s worth growing for the patterns on the trunk alone. It won’t grow huge in a planter box but it is a delight.
- Tender trees like olive and pomegranate grow well in planter boxes but will need a warm, cosy patch for the winter.
- Bonsai trees will give you endless pleasure and slow growth indoors and they do not need a very big planter either. You could double up a bonsai with another tree which would complement it, in a deep planter box and then enjoy both.
- Fir trees like Nordman fir, Norway spruce and the beautiful blue spruce can grow happily in pots. They won’t like to be brought inside for Christmas and put back out into the cold so keep your potted tree outside and decorate with twinkly lights for some festive cheer.
Plant your tree carefully, cover the roots with soil and press it down gently to ensure it is happy in its new home. Water it well and leave it alone for a few days. Once you spot some new leaves growing, you know your tree is happy. Finally, here are some tips to help your tree and planter box stay trouble-free.
What maintenance will my tree planter box need?
Depending on the material chosen:
- Metal, ceramic and composite plastic planter boxes may need hosing down every few months and dirt tends to build up if the weather has been very wet and muddy.
- Brick may need some moss removal during the spring.
- Wood needs an annual coating of varnish, stain, paint or protector to ensure it stays waterproof.
What maintenance will the tree inside my planter box need?
- Prune to keep the size and shape manageable. Some trees can only be pruned at a particular time. eg. cherry must not be pruned later than the end of the summer because the sawn branches need time to heal. Apples can be pruned during spring or autumn.
- Fertilise to help it to flower or produce fruit or nuts. Ash applied in the winter will give you excellent cherries and many other trees benefit from the goodness it provides too.
- Mulch to help it retain moisture in dry periods or to increase the fertility of the soil. You can use well-rotted leaf mould or a thin layer of compost, but not bark as this depletes the soil underneath.
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