Architectural Plants

Some plants are much more successful in containers than others.

The staff at nurseries will also be experienced in wrapping and packing awkward or unfamiliar plants, and can usually arrange the delivery of any large specimens that you’re unable to take home yourself. Delivery is normally expertly done by strong young chaps, who are used to dealing with weighty palm trees and giant bamboos. These plants will be delivered to your door and manoeuvred to any part of the garden, as requested.

All in all, specialist nurseries are hard to beat and, because most of the plants are produced on site, the cost is reasonable and the full range of stock is usually available.

However, garden centres shouldn’t be automatically dismissed. Many of them are becoming much more adventurous in the plants they stock, and increasing numbers of architectural plants can be found on their premises. Garden centres are also convenient places for buying compost, garden tools, irrigation equipment, lighting and anything else that might be required for the garden, all of which can be bought at the same time as the plants.

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There’s a wide choice of exciting plants for growing indoors too.

Financial constraints

Gone are the days when everyone lived at the same address for several decades and was able to grow plants from tiny specimens until maturity. Nowadays, many of us are impatient for an ‘instant fix’, and television gardening programmes have encouraged us all to buy large plants for immediate impact. This is fine if your budget is open-ended, in which case buy the largest of everything. Most of us, though, can’t spend our hard-earned cash with such reckless abandon and need to be a bit more cautious.

If your budget is limited, work out from your list of requirements which are the fast-growing plants and which are the slowest. If a plant is a rapid grower, putting on several feet of new growth per season, such as a Eucalyptus, then buying a smaller, cheaper plant makes sense. For plants that are tediously slow, such as palm trees, put as much money as possible into buying a decent-sized specimen. Watching a small palm put on just a few inches of growth per year is a maddeningly frustrating experience, as you know that it will be years before it flourishes enough to become a focal feature in the garden.

One last thing to give some thought to is that some of the larger plants can be extremely heavy and quite tricky to plant. So, there is often the added expense of employing a professional team of capable gardeners to do the hard work for you. It’s a choice between parting with yet more cash or risking personal injury by doing the job yourself.

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Aeonium ‘Schwarzkopf’ is a popular and easy choice for a terracotta pot.

Plants in pots

Growing plants in containers has always been popular, but the difficulties of cultivating plants in this way are often glossed over. Magazine articles and advertisements for conservatories and terracotta pots make it look so easy, and gardeners usually blame themselves when plants become unhealthy or die. But it cannot be overemphasized exactly how unhappy plants can become when forced to spend their lives in such an unnatural environment.

Plants are at least a hundred times happier when planted in the ground, where they belong, than when they are planted in pots.

The roots of plants growing in containers are far nearer the elements than they were designed for, which is tucked away snugly underground. They experience more frost, more heat from the sun and more rain, which doesn’t always drain away quickly enough. So the chances of these plants suffering from freezing, drought and rotting are far higher than if they were growing in the garden. Plant roots also like to spread out, not to be cramped in a small space, which causes the plant additional stress. A stressed plant has reduced resistance to pests and diseases. Plants in containers have to be sprayed for bugs far more often than those in the ground. Insects can detect a weakened plant a mile off and zoom in for the kill with astonishing speed.

The most common cause of failure, however, is lack of water. Watering in the summer is something we all know has to be done, but sometimes watering twice a day in periods of extreme heat is too much of a chore. During the winter, when we assume that plants are looking after themselves more, watering is a task easily forgotten. Just because it has been raining for days on end doesn’t mean our containers are being adequately supplied with moisture. The rain can bounce straight off leafy plants without any water going directly into the pot.

Sometimes, though, containers are unavoidable. If your garden consists of a roof terrace or balcony, then they are the only choice. Pots on either side of the front door or along a terrace are always popular, too. By choosing suitable containers and understanding why certain plants should be avoided, the whole process can be turned into a successful venture.

Selecting suitable containers

The traditional flower pot is a carefully chosen shape, not because of its looks, but because of its practicality. The fact that it is wide at the top, narrow at the base and has smooth straight sides means that however pot-bound a plant becomes, it can always be pulled out. This should be given serious consideration when choosing a pot for your prize specimens.

Although there are some beautifully shaped pots on the market, containers with extravagantly curved sides should be used only as ornaments for the garden. Otherwise, when it is time for the plant to be moved into something larger, the only options are either to smash the pot or to chop off a considerable amount of the plant’s root system.

Whether a pot is plastic, terracotta, ceramic or stainless steel, good drainage is vital. Unless there are really good-sized drainage holes drilled into the bottom, leave it in the shop – it is useless!

Also, bear in mind that the larger the pot, the wider the choice of plants that can be grown in it successfully.

It is interesting to remember that the French king Louis XIV had figured all this out years ago with his famous Versailles pots. They were brilliant designs that enabled plants to be kept in them for decades. Each of their four sides could be removed, which gave his gardeners access to the roots. Every year, one side only was lifted off, any dead roots were cut out and the old compost was gently tweezed out with a specially made implement – something like a small curved fork. This was replaced with fresh compost, which gave the plant a new lease of life. This meant that every four years, all sides of the plant received this treatment, which ensured that the king’s precious Citrus trees remained healthy and in peak condition.

A genuine Versailles planter costs a small fortune, but there are some good replicas on the market. Before you buy, check first that they have removable sides, otherwise they rather miss the point.

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Versailles pots with removable sides allow root pruning to be done with ease.

Choosing plants for pots

Seasonal plants such as Canna, Zantedeschia, Agapanthus and Hedychium that die back each year after flowering can all live in pots for years. Once they become too large for their pots, haul them out, divide the clumps into several plants, replant what is required and give the rest away to a gardening chum.

However, the idea of buying a splendid new pot, often at considerable expense, is usually for it to be a permanently planted focal feature, looking attractive all year round, not for just a few months in the summer.

Plants that never get any bigger are ideal. Box (Buxus) balls, bay (Laurus nobilis) lollipops, yew (Taxus) cones and Japanese pom-poms such as Ilex crenata are perfect, as long as they are clipped regularly to keep them in shape. During the growing season, clipping must be done little and often so that the foliage doesn’t become straggly and unkempt. If the foliage is allowed to grow, more stress is put upon the root system as it struggles to support the extra leaves.

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Zantedeschia aethiopica ‘Crowborough’ can live in a pot for years if it is well watered.

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Japanese topiary such as Ilex crenata are blissfully content in large terracotta pots.

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Slow-growing plants like Trochodendron aralioides are happy to spend the first four years of their lives in containers.

For something a little more unusual, try the silver-leaved Corokia x virgata from New Zealand or the dense form of Euonymus japonicus ‘Compactus’.

Another category that contains some interesting choices are those that are very slow-growing and evergreen. There really is little point in choosing anything deciduous: nobody wants to look at a pile of sticks in the winter if the container is in a prominent part of the garden. The Dwarf Fan Palm, Chamaerops humilis, is happy in a pot for years. So is the dwarf Pittosporum tobira ‘Nanum’. This lovely glossy-leaved plant has highly scented flowers in the summer and can be grown in a pot quite easily. Tree ferns such as Dicksonia antarctica are happy enough, too, as their root system takes years to outgrow a large pot. Hebe rakaiensis is another good choice. This plant grows to a 90cm (3ft) mound and then stops, although clipping is still advisable to keep it extra tidy. Consider a rare tree as well: Trochodendron aralioides is slow-growing, tolerant of neglect and essential for any gardener wanting to grow something really unusual.

There is also a wide range of small succulent plants available, all of which are quite content to sit in pots. Try Aloe aristata, Echeveria glauca, Aeonium arboreum and the purple variety Aeonium ‘Schwarzkopf’.

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Euonymus japonicus ‘Compactus’ is an unusual leafy choice for a pot.

Finally, there are the strongly architectural spiky plants. Most of these come from desert regions, which mean they have had to adapt to burning hot sun during the day, freezing temperatures at night and long periods of drought, making them admirable choices for containers. Most hardy Yucca suit this purpose for the first few years of their lives, especially Yucca gloriosa and Yucca aloifolia. The wonderfully spherical Dasylirion acrotrichum can live in a pot for years. Probably the most spectacular of all is Agave americana. This plant and its various coloured forms all look stunning in terracotta pots.

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Agave parryi and most other desert succulents almost enjoy being in pots.

Compost

With the exception of tree ferns, which require a peaty compost, most plants are blissfully content in a loam-based compost, such as John Innes no. 3. Stir in up to 50 per cent of extra grit to provide really sharp drainage. This eliminates the need to fill the bottom few inches of your pot with large crocks as we are often advised to do. Loam-based compost is heavier than a peat-based mix, which helps to stop pots blowing over in the wind. It also has more nutrients and is easier to re-wet if the whole pot dries out.

Feeding

Plants in pots need all the help they can get, and this includes regular feeding throughout the growing season. In spring, start off by giving each pot a good dollop of something strong, such as a mix of blood, fish and bone. Thereafter, add a small dose of foliar feed to each watering can and use every time you water, even if it’s every day. Vital nutrients are easily leached out of pots, leaving plants prone to yellowing. The aim is to have handsome foliage that looks in the peak of health, not jaundiced and miserable.

Watering

The all-important task of irrigation must be taken seriously. The compost should never be allowed to dry out completely, which is quite an onerous task in the middle of a heat wave. Having pots within easy reach of a hose helps, so does having a garden tap. Plants in pots need watering virtually every day during the summer months, so careful planning is needed. Don’t wait for the summer to realize that each plant is a long way from a water supply – carrying heavy watering cans soon becomes a chore.

Alternatively, think about installing an automatic drip-irrigation system. Each pot has the recommended number of ‘drips’ pushed into it, all of which are connected to a long length of tubing plumbed into the water supply. The timer is then set to come on for as long and as often as you wish. The cost of these irrigation systems has decreased considerably as their popularity has increased, and they are now available at all good garden centres. Most are now fairly easy to install without expensive plumbing costs.

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Plants such as Azorina vidalii can stay glossy and healthy-looking if fed and watered correctly.

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With regular irrigation, Cycas revoluta can look fantastic in a pot.

Pests & diseases in pots

Plants in pots are much more prone to attacks from various beasts and general disorders than plants in the ground. Keep a constant watchful eye and catch them at the first sign. (See the chapter on pests, diseases and other disorders on pages 334–347.) One particularly nasty horror is the dreaded vine weevil. This sneaky, vicious brute lurks under the soil feeding on the roots of your precious specimens. One day, your plant collapses with no warning and the top comes off in your hand – no roots left at all! By scraping around under the soil, large fat white grubs can be found (they’re large and fat because they have been gorging on the entire root system). Other signs to watch out for are nibbled notched leaves, which are made by the adult form of this nocturnal creature.

Once found, dispose of the entire contents of the pot, fill it with fresh compost and start again. There are some exceptionally nasty chemicals around that can be added to the soil to ward off vine weevil, but using a loam-based compost and giving an occasional dose of a natural predator (a nematode worm that eats only the bad guys) works very well. Vine weevils are lazy things and prefer to burrow through soft, peaty compost rather than heavier loam.

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Echeveria glauca is a favourite snack for vine weevils.

Overwintering

No plant will stand having its roots frozen solid for weeks at a time. If you have a nice little courtyard garden in a warm inner city or if you live in a mild area near the sea, then this won’t be a problem. In colder areas, pots may have to be moved indoors or wrapped up. Choosing very hardy plants is obviously sensible, but the roots would still remain vulnerable. If cold winters are a regular occurrence in your part of the world, before planting, line the inside of each pot (excluding the bottom) with a thick layer of bubble wrap. This is completely invisible once the pot is planted up and much more pleasing to the eye than an old blanket wrapped around the outside of the pot.

Moving a heavy pot that has been planted up to less cold conditions indoors can be rather a nuisance. There are various trolleys and sack barrows on the market, but the best one I’ve come across has a beautifully angled shape and heavy-duty pneumatic tyres, which make light work of the whole procedure.

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Canna indica can easily be overwintered under glass if it is planted in a container.

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Aspidistra elatior is a nice leafy choice for a pot.

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The blue form of Agave americana looks beautiful next to the colour of terracotta.

Conservatories

Conservatories have never been more popular. Having a garden room attached to the house, where one can wander into a different climate and enjoy all the leafy and floral delights that are too tender for outdoors, is a splendid idea. The image often includes reclining in comfy chairs and occasionally reaching out languidly to pick a home-grown juicy citrus fruit or maybe a ripe fig. A place where the last rays of the setting sun can be observed at the end of the day …

If only reality could match the dream. Nothing prepares conservatory owners for the difficulties of growing plants in this kind of environment. The glossy adverts are taken at face value, and the fact that there are myriad problems to overcome can be a bit of a shock. The previous pages dealt with growing plants in pots, but growing plants in pots and under glass takes the art of cultivation into a new league altogether. Plants hate the excessive heat, dry atmosphere, lack of ventilation and the extreme variations of seasonal temperatures often found in conservatories.

The better the environment in the conservatory, the larger the range of plants that can be grown successfully.

Choosing a conservatory

Buy the largest conservatory that you can accommodate and afford. The larger the space, the easier it is to maintain a balanced climate. Instead of automatically siting a conservatory on the sunniest side of the house, consider a shadier spot where the heat of the summer is less intense. If possible, choose a structure with a door at each end. This will allow a good flow of air during the summer to help keep the interior cooler. Gentle breezes are what we are aiming for, not howling gales, so a sheltered part of the garden is required, not an exposed corner.

Ventilation is a boring, but essential, subject to think about as well. It is almost impossible to have too much ventilation, especially in the summer. Most conservatories are not well designed in this department, offering just one or two feebly inadequate vents in the roof, if you’re lucky. It is worth paying extra to have as many fixed panes of glass in the roof as possible converted into movable ones that open. If the design allows, have some side vents fitted as well, to catch the breeze from all directions.

Flooring

As all plants are much happier growing in the ground than they are in containers, leaving some space in the conservatory floor, where small trees and faster-growing plants can be planted directly into the soil, is something worth thinking about when you are planning your conservatory. The roots would have the benefit of being able to spread out naturally, while the glass overhead would protect tender foliage from the frost.

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Tropical, lush verdancy is what we’re aiming for in a conservatory.

Also consider choosing the sort of flooring that can be hosed down in the summer. This would help to lessen the heat while increasing the humidity, both of which would benefit the plants. Fluffy rugs might look okay flung on the conservatory floor, but they are not exactly practical.

Watering

Having a hose pipe right where it is needed will make watering much less of a chore, and your plants are therefore more likely to be irrigated when they need it, rather than having to wait until it is convenient.

Automatic irrigation systems have improved hugely during the last few years. Available from all good garden centres, they are easy to install, reliable and reasonably priced. A main pipe is placed all around the conservatory, and from this numerous drip nozzles can be pushed into each container. The timer is as easy as any domestic central heating or hot water system. They are the perfect solution for anyone who is frequently away from home or who would prefer spending their time doing other things.

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Strelitzia reginae adds an exotic air to any conservatory.

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The size, aspect, ventilation and maintenance of a conservatory have a direct bearing on what can be grown successfully.

Heating

From being boiling hot in the summer, the temperature in many conservatories plummets during the winter when the heat is quickly lost through the glass. Many plants can cope with almost freezing conditions, but a few degrees above freezing will make life more pleasant for plants and humans alike.

Whether the conservatory is heated by leaving the door to the adjoining house open, or by radiators, hot pipes, portable gas heaters or anything else, it is important to remember that plants do not like direct heat, so keep them some distance away from any heating source. Avoid heating systems that blow hot dry air directly onto the plants’ foliage as this can make the leaves turn brown and crispy.

If possible, avoid underfloor heating as well. Although this is nice for cats and people to walk on, plants hate this much heat so near to their roots – they will start to shed their leaves almost immediately. The only plants able to tolerate underfloor heating are spiky and succulent ones that are used to coping with the heat of their native habitats, such as the Sonoran Desert in Arizona or the warm plains of South Africa. Lovely though these plants are, most gardeners prefer to grow a variety of plants under glass, and the sharp spines of Yucca and Agave can be inconvenient indoors.