Planting and Growing Hedge Plants in Containers
This guide will help you with planting and growing hedge plants in containers. To skip to a particular section click on the links below:
For those gardens that do not have the bare earth for direct planting (and this includes far too many front gardens and, of course, patios), the container comes to the rescue. Fortunately, many hedging plants will happily grow in a container. But, to paraphrase Mrs. Beaton: first choose your pot…
Containers are available in many different materials but it is essential that whichever you choose, it has drainage holes. Each type has advantages and disadvantages:
Clay and Terracotta
The most traditional of materials, clay and terracotta have the added advantage of suiting just about every garden style. However, they are prone to crack when the frosts come and also dry out quicker in the spring and summer, and therefore you will need to water them a little more frequently when the sun’s out. For added reassurance and insurance:
- Always choose frost-proof pots
- Protect them in winter by wrapping in bubble-wrap, sacking or a similar material
- Stand them on feet and remove saucers in winter. This will help protect against waterlogging – an equal, if not bigger, threat, than frost damage. (You can, of course, keep the feet in place throughout the year)
- Move them to a more sheltered spot for winter (If your containers are too large and therefore too heavy to move easily, make sure their location is not over-exposed)
- In dry periods during summer, check the compost regularly and water if dry
Plastic containers are lighter than clay or terracotta and can therefore be more easily moved – an important consideration if heavy lifting isn’t your forte or you simply don’t fancy it. They also retain moisture better and less watering is generally required.
Aesthetically, plastic containers now come in such variety that you should have little difficulty in finding pots to suit your taste and garden – the mock terracotta ones are particularly popular and the best are virtually indistinguishable.
Probably the material of choice for the modern-style garden. Always choose a galvanised (or other rust-proof) metal.
While frost won’t crack them, they do get colder in winter and particularly sensitive hedging plants should be protected with bubble wrap and/or sacking. In the summer they will retain moisture well but if placed in full sun can overheat.
Wooden containers are an excellent compromise – they won’t crack in winter and retain moisture in summer. But wood is a natural material and will, therefore, eventually rot. A wood preservative can add decades of life but make sure that the preservative cannot permeate into the compost and poison it. A plastic lining is advisable – but do remember to make holes in the bottom for drainage.
The traditional half-barrel works well (especially with a lining), though the metal hoops can rust. It is therefore worthwhile painting the hoops carefully with a weather proof paint or other coating.
Raising a wooden container so it does not touch the ground will also help prevent premature rotting.
Stone: Stone containers can make an attractive alternative, though they tend to be on the heavy side. Choose only frost resistant containers and protect in winter as above. They retain moisture reasonably well.
Over the last few years, these large bags normally used to deliver sand, gravel etc in bulk have become increasingly popular as garden ‘containers’. They’re cheap, provide more than enough depth but only come in white and, once they’re in position and filled, impossible to move. If you go this route, remember to puncture the base with at least a dozen drainage holes and to use gravel rather than crocks (which could puncture the bag) for drainage. Rather than filling with just proprietary compost, you can put 10-15 cm of garden waste and compost on top of the gravel before filling with compost.
Having chosen your preferred pot material, the next (and more important) decision is to buy pots of the correct size. Although it is tempting to put small plants in large containers, the plants, counter-intuitively, won’t thank you for it. Instead, start off with containers large enough to take the roots with 6-8cm spare at the widest point. This will encourage the plant to grow strongly and you will not need to repot into a larger container for 2-3 years.
All of the hedge plant suggestions that follow in the next post will be happy in a loam-based compost such as John Innes No 3 or similar. First though, you must add some broken crocks and/or gravel at the base to a depth of at least 5cm. This is essential to help good drainage. In larger pots (and particularly builders’ bags), a good layer of garden compost or waste can be added.
If you are using proprietary compost you will not need to add any fertiliser for 4-8 weeks (see, as they say, the pack for details). In spring, once the fertilizer in the compost has run out, add a general purpose, slow-release granular feed according to the pack instructions. Nitrogen is the key nutrient for growth. Don’t over-feed. Organic granular feeds are available. There should be no need to feed from late summer to the end of winter.
At the beginning of their second spring, top dress the containers by carefully removing around 5cm of the compost and replacing it with fresh, mixing in fertiliser granules as above.
Trees and shrubs in containers will dry out far more quickly than those growing in the ground which is why watering correctly is the make-or-break of container gardening. Remember that the plant’s own foliage can prevent rain from reaching its soil, so don’t assume that if it has rained, your plants have been watered.The compost should always be moist, but not sodden – even during winter when the wind can dry it out. From April to September, you should, ideally, check containers daily, especially during hot weather. Watering, whether with hose or can, should be done twice- fill the container to the brim and allow the water to filter down. Then repeat. This is the best way to ensure all of the compost has been wetted.
If the water is not draining freely, check the drainage holes and unblock as required. Mulching will help deter weeds and moss but will only have a minimal effect on water retention.
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 or hessian, held securely in place with twine.
In winter, the two main enemies are frost and waterlogging.
The smaller the container, the more at risk will its plant be from cold weather. Wrapping in bubble wrap or sacking offers good protection as does moving the container to a more sheltered spot, putting feet under it and removing saucers. The last three preventative measures will also help prevent waterlogging during particularly wet periods.
Fortunately, container grown hedging plants can tolerate cramped conditions providing they are otherwise well-cared for. Indeed, a compact plant may grow more slowly, but it will also grow strongly and produce better foliage.
Nonetheless, the time will come when your hedge plant will need to be re-potted into the next size of container or, at least, given completely fresh compost. This will generally be after two or three years and though a plant can be kept alive in the same pot and compost for much longer, it will be increasingly at risk from adverse weather, pests and diseases.
Here’s how to re-pot:
• Repot in early spring as soon as there are signs of new growth
• Remove a little of the compost, tease out the plant and its roots – don’t be afraid of cutting the roots if necessary
• Use fresh crocks and/or gravel to prevent transferring any disease that may be present
• Replant in fresh compost
• Once your plant is in the optimum size container, replace he compost every other year – in extremely large containers, simply replace at least one third of the compost every other year
The following hedging plants will all happily grow in containers:
- Beech (Fagus sylvatica): One of our most popular trees, the Beech can be container-grown and still give of its best
- Box (Buxus): Box Balls and Pyramids make excellent container plants, adding structure and a sense of simple formality to a garden. Often used in pairs or rows either side of a door or bed
- Dwarf Box (Buxus sempervirens ‘Suffruticosa’) makes a perfect container centrepiece for companion planting with annuals, low-growing herbs or dwarf Lavender
- Escallonia macrantha Rubra ‘Crimson Spire’: Will need repotting sooner than most – but worth it for decorative glossy foliage and a dark red floral display that lasts from summer through autumn.
- Euonymus fortunei ‘Emerald ‘n’ Gold’: This dwarf evergreen with green and yellow-gold foliage looks great in a smaller container
- Euonymus fortunei ‘Emerald Gaiety’: More subtly variegated than its cousin above, Emerald Gaiety makes an elegant and bushy container shrub
- Hornbeam (Carpinus betulus): Like Beech, the Hornbeam makes a superlative container-grown focal point
- Cherry Laurel (Prunus laurocerasus ‘Rotundifolia’): As robust as it is attractive, the container-grown Laurel may need a stake or two to keep its shape
- Leylandii (Cupressocyparis Leylandii): Grown in a container, the Leylandii’s growth can easily be kept in check
- Perovskia Blue Spire (Perovskia atriplicifolia ‘Blue Spire’): Although not normally grown in containers, if this is the only way you can get this stunning plant into your garden, take it. As it looks its best in a clump, choose a medium to large container and plant five or more as space allows. Even better, take a larger container, surround a central clump with dwarf lavenders – one of the great horticultural pairings
- Photinia Red Robin (Photinia x fraseri ‘Red Robin’): The choice for a vibrant splash of red.
- Privet ( Ligustrum vulgare): Faster growing than Box, container-grown Privet is best when shaped and is the plant of choice for first-time topiarists
- Purple Copper Beech (Fagus sylvatica ‘Purpurea’): The showiest of the Beeches is perfectly at home in a container.
- Yew (Taxus baccata): Like the Beech above, Yew too will grow well in a container. Every garden can, and should, have one
And finally: The Cheat’s Hedge
For those who want the benefits of a hedge but whose back and/or front plot does not allow direct planting (patios are an invaluable element of most gardens, but are not a replacement for a garden), container planting is the solution. A closely spaced row – straight or curved – of container-planted hedging plants will, as the plants grow and their branches ‘knit’ together, provide the aesthetic and screening effect of a hedge.