Growing Trees in Containers

Re-Potting and Aftercare

 

Growing trees in containers is ideal for commercial settings, small gardens or where space is limited, or areas where planting in the ground is not possible, such as on a patio or terrace. They can bring height, fruit, bark and autumn colour into these small spaces.

 

 

Repotting and aftercare of trees for exterior settings

- Make sure the compost in the present tree isn’t too wet when repotting.

- Loosen the compost at the edges of the pot and pull the tree out by the base of the main stem.

- If the tree is very tight in the pot you may have to carefully cut down the length of the pot on at least two sides to release the root system.

- Once out of the pot, if your tree has become root bound, it may well benefit from some root thinning and pruning.   

- Add a 5cm layer of clay pebbles at the bottom of the pot for improved drainage and aeriation of the roots (Click HERE and HERE for              suppliers).

- Add some extra compost mix on top of the clay pebbles before you insert the tree. You need to add sufficient compost so that the top of the rootball will be 2 to 3cm below the top of the pot to allow for a top dressing. (See below* for our recommended composts).

- It is essential to ensure that the trunk of the tree is slightly proud of the surrounding compost. This will enable the plant to naturally settle into the fresh compost without sinking below it, which is very important to avoid. Otherwise, the trunk may be vulnerable to wet rotting and soil-borne fungal diseases.

- Fill in around the plant with the compost mix in small amounts at a time, tamping it down to ensure that there are no air pockets.

- Top dress with decorative stones, clay pebbles or bark mulch. This not only looks attractive, but also reduces water loss from the soil by evaporation.

- Remember that it is essential to keep the compost moist, and always avoid the planter ever drying out, which can happen in a single day during the hottest periods of the year. Even in winter keep the soil moist, as evergreen trees, in particular, are constantly losing water by transpiration from the leaves.

 

Composts for Trees in containers

 

As trees prefer to be in the open ground it is critical that the correct compost to optimise the health of trees. The soil should maintain sufficient aeration and drainage while retaining suitable amounts of moisture. Good container soil retains adequate levels of water without becoming waterlogged.

Most trees will grow well in the loam-based compost, heavy enough to provide good support and a source of minerals. However, we recommend a high quality blended Peat Free potting tree compost, such as Westland Peat free tree and shrub potting compost or Melcourt Sylvagrow Peat Free compost with added John Innes loam based compost with clay pebbles in the base of the pot, both of which will provide good drainage and improved aeration.

Avoid cheap fluffy composts, often found on offer in garden centres and larger stores.

 

Compost for most tree species

 

We recommend Melcourt Sylvagrow Peat-free with John Innes No3 (JI3) . Click HERE

• A unique blend of fine bark, woodfibre (by-products of sustainably managed British forests) and coir (from known, ethically-approved sources) plus sterilized loam and sand.

• Contains balanced nutrients sufficient for the first 4 - 6 weeks of growth.
This growing medium is based on one widely used throughout the UK by professional growers and is suitable for a wide range of uses around the garden.

• Contains no peat or green waste compost.

 

Compost for Ericaceous trees  

Acid-loving trees such as Azalea, many Acers, Camelia, Most Magnolia spp*, Rhododendron, the Strawberry tree, (Arbutus unedo), Taxus should be planted in loam-based John Innes Ericaceous compost.

We recommend Melcourt SylvaGrow Ericaceous. Click HERE.

*See appendix – Growing Magnolia species in containers.

Two other good options are John Innes Ericaceous Compost, and Westland John Innes Ericaceous Peat Free, which are both excellent for Rhododendrons, Azaleas and Camellias.

 

Compost for fruit tree species

You may want to consider pure Organic compost. We recommend  SylvaGrow Organic. Click HERE

 

Additional Slow Release Tree Fertilizer

Most composts have limited nutrient supply, so we recommend With all the above we recommend after the first month to add 6 month slow release feed and added zinc complex, this blend ensures your best ever trees and shrubs. Osmacote. Click HERE

Your tree may need to be re-potted after a few years if it has outgrown the planter. Over time, trees in pots deplete the nutrients in the potting soil making it important to either repot the plant or replace up to 25% of the compost every couple of years.

 

 

Select the right tree.

Trees suitable for planters exterior settings

·         Japanese maple.

·         Amelanchier

·         Myrtle

·         Magnolia varieties  

·         Topiary specimens of box, yew, bay, privet or holly, cloud trees

·         Conifers, such as Italian Cypress

·         Dwarf conifers such as Yew, Pinus mugo, Chaeycyparis and Juniperus

·         Palm trees, including Trachycarpus fortuneii, Chamaerops humils, Brahia armata, Butea capitata Phoenix canariensis and Cordyline                    australis

·         Something unusual like Sophora microphylla or Albizia julibrissin.

·         Fruit trees including crab apple, Fig, Olive, Peach

·         Tender trees, Pomegranates and Citrus are ideal in pots

·         Banana trees, including  Musa basjoo and the striking Musa Red Abyssinian Banana – Ensete ventricosum Maurelli

 

Reliable Tree Suppliers - Contact Barcham Trees (Click HERE) and Chew Valley Trees (Click HERE) for advise and available options.

 

Fastigiate Olive trees in Self-Watering Planters

 

Many people are over ambitious, and choose a species that will quickly outgrow the container, requiring a lot of water and nutrients and prove difficult to keep upright. Excellent slow growing options include Olive trees, Magnolia stellata, hollies, Buxus, compact conifers, Japanese maples and Viburnum.

Chew Valley Trees and Barcham Trees both have an excellent range of smaller slow growing species, and will give you good advice for the best species and variety to choose.

Select the best style and size of container

   

Polystone Tree Planters

 

Choose as large a planter as possible for the setting, as small containers dry out more easily, become root-bound quickly, constricting the roots.

They are also prone to fall over more, particularly if the sides taper inwards. Anchoring top-heavy young trees in pots is tricky, so you really need a deep container to attempt this feat. If space allows, substantial planters are the best bet. Bear in mind that most trees and shrubs want to send roots down between 30 and 60cm, at least.
 

Tree Planter options that are available in larger sizes include:

   

Aftercare for container trees in exterior settings

 

Watering

Lack of water is the main cause of poor growth, and the associated disease of the leaf, which inevitably occurs as with any plant, if the  plant continuously dries out.

It is essential to never let them dry out, as this can be fatal, and is the main cause of losing trees grown in containers. Your tree in a container is more at risk of drying out due to high temperatures and drying winds as they are usually exposed to more warmth and wind than those in the ground, as there is a limited supply of water in the container, and the roots cannot grow towards water sources, as they would in the ground.

It is advisable to water every day in spring and summer. Self-watering planters, or the use of water reservoirs inserted when planting can significantly increase the time between watering sessions. Use of water-retaining granules and mulch on top of the pot will similarly also help reduce the risk of drying out. Bear in mind that hardly any rainfall gets into the containers in the quantities required, particularly if your tree has dense foliage overlapping the sides of the planter. Apply plenty of water, as opposed to a light sprinkling, which will only penetrate the top few centimetres at the most.

At the same time that drying out is essential, you must avoid water logging or flooding of the compost. This will not happen if you provided good drainage when planting your tree.

To ensure that the water gets into the root ball water at the base of the trunk, and thus avoid it overflowing down the sides of the pot, gently make five or six 1 cm diam x 2cm deep holes in a circle with a dibber into the surface of the rootball about 15-20cm away from the trunk, so that the water passes into the plant rootball. It is quite a good idea to dress the surface with decorative grit. The lighter coloured the better.

If the top inch of soil becomes dry, give the tree a nice deep watering and make sure the excess water can drain away.

Over winter reduce the watering. Remember that evergreens can lose water from the plants throughout the year, so take care to avoid the pot drying out during winter.
 

Feeding

Give trees a boost, by refreshing the top layer of compost annually in spring. Carefully scrape away about 5cm (2in) of compost from the surface and replace with fresh compost – mix in some controlled release fertiliser granules, as described below

Trees, in particular evergreen species, will easily deplete the compost of nutrients, and it is essential to top them up each year. Feed your trees with ‘Oscacote’ in spring. Click HERE for a supplier.

If your plant has lost leaves in winter and you want to give it an additional boost, apply ‘Maxicrop Complete Garden Feed’ fortnightly over the Spring to ensure the tree stays healthy and vigorous. Using the earlier recommended loam based compost will help to retain and release nutrients.
 

Alternative organic fertilizer enriched with Biochar.

Carbon Gold Tree Fertiliser blends enriched biochar* with potassium phosphite to grow healthier, more vigorous plants in the harshest conditions. Carbon Gold Tree Fertiliser contains Potassium phosphate which delivers essential nutrients for tree health, mycorrhizal fungi maximises nutrients and water uptake, the seaweed provides essential minerals and trace elements, and the organic wormcasts are full of beneficial bacteria crucial to healthy root systems.​ Click HERE for a supplier

The Nue-Tree 16-25-6 CRF Tree Planting Fertiliser is a high quality, Controlled Release Fertiliser (CRF) developed specifically for planting hole application. It is suitable for all trees. Click HERE for a supplier

*Biochar –For more information Click HERE.

 

Coping with excessive winds

It is important to be aware that trees and tall shrubs are vulnerable to blowing over in high winds when planted in containers. Also, animals and children can topple over container planted trees. We therefore always recommend to use either a cube shaped planter, or circular planter with vertical sides. Also position the tree in a sheltered location away from extreme winds. Alternatively, use a planter that has substantial weight, such as the Terracotta style. If you still feel that it is vulnerable to toppling over in high winds, either use additional heavy stones in the base of the planter, before repotting, or if appropriate, secure the tree or planter to an adjacent structure such as rails of posts.
 

Protection over winter

In exposed gardens, plants in containers will need protecting during winter as the roots growing near the edges are vulnerable to freezing temperatures. Wrap the container with bubble wrap, fleece or hessian, held securely in place with twine. This particularly applies to tree in Metal planters.

Pest and Disease Control

Although trees are naturally vulnerable to a whole range of pests and diseases, if you have kept them watered and fed, as advised above, you will have limited problems. However, some species are particularly vulnerable, and it is important to seek advice for treatments. We recommend natural methods, which are usually very affective. There are some root pests that can be devastating, and only noticed when the tree unexpectedly shows dramatic symptoms. These include pests such as vine weevil, slugs and snails, which can munch away at roots or leaves. These infestations require immediate action, including finding the source of the predator, such as under the pot or in the compost itself. Again, in most cases there are natural pest control methods available, such as application of vine weevil nematode predators. Click HERE
 

What to do if your tree outgrows the planter

There may come a time when your tree outgrows your planter and it's time to consider root pruning, and/or increasing the size of the planter. To stimulate smaller feeder roots to grow and control the plant’s size, the tree should be root pruned every 2 to 3 years. This is important because over time, roots will circle inside the pot and may girdle the trunk, which constricts the flow of water and nutrients to the canopy and could kill the tree. Root pruning will remove circling roots and encourage a healthier root system. Click HERE for a good YouTube video to demonstrate root pruning.

Alternatively, you may wish to move your tree or shrub into the ground. If the roots are already tangled and pot-bound, it might be too late, but if there's a nicely branched root system which can be teased out to stop it circling, your plant may enjoy a future in the soil, its feet will be free to roam through the wide expanse of cool and nutritious earth!

If you have planted your tree as described above and kept up the maintenance, it will thrive for many years of healthy growth, providing you with endless pleasure.