The Complete Guide to Growing Plants in Pots and Containers

Most people treat container gardening as a compromise — the fallback when there is no border to plant into. That thinking sells it short. Some of Britain's most striking outdoor spaces are built entirely from pots, with every bit of the drama of a planted garden and a flexibility that ground planting can never match.

The difference between a container display that looks extraordinary year after year and one that struggles through a single summer comes down to a few decisions made early. Get the pot right. Get the compost right. Build a watering habit that fits the plant. Everything else — feeding, overwintering, repotting — follows naturally from those foundations. This guide covers each in plain terms, so you spend less time troubleshooting and more time enjoying what you have created.

Choosing the Right Pot

The pot is doing more work than it looks. It is the entire root environment — regulating temperature, holding moisture, and either draining freely or holding water that will rot roots if it sits too long. Material, size, and drainage all matter, and not every pot is equal.

Material: What the Walls Are Made Of

Terracotta breathes. The porous clay walls allow moisture to evaporate from the sides, which helps prevent waterlogging and keeps roots cooler in summer. That same porosity means compost dries faster, so terracotta suits plants that prefer to dry out between waterings — bay, olive, lavender, and most Mediterranean species. It is heavy and can crack in hard frosts unless frost-proof grade is specified. Look for the words "frost-proof" on the label before buying. Ordinary terracotta is not guaranteed to survive a British winter intact.

Plastic is lightweight and retains moisture longer than terracotta — useful in hot summers but risky in wet winters if drainage is poor. A good-quality plastic pot with large drainage holes works well for most plants and will not crack in frost. The trade-off is that cheaper grades become brittle after a few years of UV exposure, and the aesthetic rarely flatters a considered display.

Fibreglass and glassfibre-reinforced concrete (GRC) are the premium choice for large statement planters and matched entrance pairs. They handle frost without cracking, hold their shape indefinitely, and weigh far less than stone or cast concrete — which matters on balconies and decking with weight limits. Aesthetically, they can replicate lead, brushed zinc, or aged stone convincingly and at a fraction of the cost.

Stone and cast concrete last a lifetime and look the part, but they are cold in winter — roots suffer when pot walls stay near freezing for extended periods — and very heavy to reposition. Raise them off the ground on pot feet to improve drainage and reduce the cold travelling upward from the ground through the base.

Size: Almost Always Bigger Than You Think

The most common pot-sizing mistake is choosing one that looks right today, not one that will support the plant through a full season of growth. A pot that looks proportional when a plant goes in will typically be congested within a season and struggling within two. The general principle: the pot should be at least 5 to 7 centimetres wider than the current root ball, and proportionally deep. For standards, shaped lollipops, or large shrubs, plan for a pot of at least 40 to 50 centimetres in diameter to keep the plant fed, hydrated, and anchored without blowing over in wind.

Drainage: The Detail That Cannot Be Skipped

Every pot needs holes in the base. If you have a decorative planter with no drainage, drill it — or use it as a cachepot, placing a plastic pot with drainage inside it on a layer of gravel or pot feet. Water sitting in a sealed base will rot roots within days in warm weather. Raise pots on feet when they sit on flat paving, to prevent drainage holes being blocked by suction against the surface.

Compost: Not All Bags Are Equal

The cheapest bag of multipurpose compost is not automatically wrong, but understanding what each type actually does will save you a lot of unnecessary replanting.

John Innes vs Multipurpose

Multipurpose compost is light, affordable, and good for annuals and short-term seasonal planting. The problem is that it breaks down quickly — typically within one to two years — compacting, shrinking, and losing its open structure. For anything permanent, it is not sufficient on its own.

John Innes No. 3 is loam-based, heavier, and far more stable for long-term plantings — shrubs, standards, shaped evergreens, and anything you plan to keep in the same pot for more than one season. Its structure holds for several years. A reliable starting point is mixing John Innes No. 3 with multipurpose in a 60:40 ratio. This gives good drainage, structural stability, and a nutrient reserve to support the first season of growth.

Specialist Mixes and Additives

Ericaceous compost is acidic and essential for rhododendrons, camellias, pieris, and other acid-loving plants. Using standard compost for these will cause yellowing leaves within a season as the plant cannot absorb nutrients at the wrong pH. For Mediterranean species such as bay and olive, adding horticultural grit to the mix — around 20% by volume — improves drainage and substantially reduces the waterlogging risk that is the most common cause of decline in those plants. A 3 to 5 centimetre layer of grit or broken crocks placed at the base of the pot before adding compost helps excess water escape freely and reduces the chance of drainage holes silting up.

Watering: The Skill That Separates Success from Struggle

Overwatering kills more potted plants in the UK than underwatering. That surprises most people, but it is consistently true. Roots need both water and air. When compost stays wet for days on end, roots begin to rot, the plant wilts, and the owner — seeing a wilted plant — waters it again, completing the problem.

The most reliable method is the finger test. Push a finger 3 to 4 centimetres into the compost. If it feels damp, leave it. If it feels dry at that depth, water thoroughly until it runs freely from the drainage holes, then stop. Never give plants a shallow daily dribble — water deeply and less frequently. This encourages roots to grow downward, producing a stronger and more drought-tolerant plant over time.

In summer, established plants in full sun may need watering daily. In autumn and winter, most will need watering once a week or less, if at all. Let the season drive your frequency, not a fixed routine. Compost that stays wet in cool, dark conditions is the single most common cause of root rot over winter.

Feeding Your Potted Plants

Plants in containers depend on you for nutrients in a way that ground-planted specimens do not. Rain, drainage, and regular watering constantly leach nutrients from compost. Within six to eight weeks of potting, most of the plant-available nutrition in a fresh bag of compost has already been washed through. From that point, the plant is running on what you give it.

A balanced slow-release granular fertiliser applied in spring — worked lightly into the compost surface — is the simplest and most effective approach for most ornamental shrubs and shaped plants. Products such as Osmocote, or any similar coated slow-release formula, will feed consistently for three to six months. Supplement with a liquid feed every two weeks through the growing season (March to September) if you want to push performance — a seaweed-based feed or balanced NPK liquid both work well.

Overwintering: What Actually Needs Protecting

Potted plants are more vulnerable to cold than the same species planted in the ground. In the ground, the surrounding mass of soil buffers roots against frost. In a pot, the root ball can freeze solid when the pot walls are thin and temperatures drop below minus three or four degrees Celsius. Most UK-hardy evergreens will handle brief frosts without damage, but extended cold spells are different, especially for borderline-hardy species.

The most effective actions: move vulnerable pots to a sheltered spot — against a south or west-facing wall, or under an overhang — wrap pot walls in hessian, bubble wrap, or fleece to insulate the root zone, raise pots off the ground to stop cold travelling upward through the base, and cut back watering dramatically. A frozen wet root ball is the most destructive combination a container plant will face over winter.

Fully hardy plants — box, yew, holly, Portuguese laurel — rarely need pot wrapping in most UK regions unless temperatures are forecast below minus eight. Semi-hardy plants — olive, bay, phormium, cordyline — benefit from protection whenever temperatures are expected to fall below minus five. Truly tender plants such as citrus or bougainvillea should come inside entirely once temperatures consistently fall below zero. Be honest about what a plant is. Labelling something as "hardy" does not mean it is happy in a frozen pot on an exposed north-facing terrace in January.

Repotting: When and How

Roots growing through the drainage holes, slow growth despite regular feeding, and compost that dries out within hours of watering are all signs that a plant has run out of room. Most container plants benefit from repotting every two to three years, moving up one pot size — roughly 5 to 7 centimetres wider — each time. Jumping too far up in size in one go is a common mistake: excess compost around the roots holds moisture the plant cannot use, which increases rot risk rather than solving the problem.

Spring — as the plant comes into growth — is the best time to repot. This gives roots an entire growing season to establish in fresh compost before the next winter. When repotting, tease apart any circling roots at the base of the root ball, remove the bottom third of exhausted old compost, and fill around with fresh John Innes No. 3 mix. Water well after repotting and place in light shade for a week to reduce transplant stress.

When a plant has reached its final pot size — as often happens with large shaped standards or architectural specimens — top-dressing is a practical alternative to a full repot. Scrape away the top 5 to 8 centimetres of old compost and replace it with fresh, then apply slow-release fertiliser to the surface. This refreshes the nutrient profile and improves surface drainage without disturbing the established root system.

Frequently Asked Questions

What plants look good in pots all year round?

Evergreen structural plants are the backbone of a year-round container display. Box balls, shaped Portuguese laurel, yew cones, or holly standards give consistent form and presence in every season. Around them, rotate seasonal interest: spring bulbs underplanted at the base, summer lavender or ornamental grasses, autumn sedums, and winter heuchera or euonymus for low colour. The evergreen anchor stays; the seasonal layer changes around it. One good structural plant in a generous pot is worth more than three struggling ones in undersized containers.

How often should I feed plants growing in containers?

Apply a slow-release granular fertiliser once in spring, then supplement with a liquid feed every two weeks from April through to mid-September. Stop all feeding by late September to allow the plant to harden off before winter. Over-feeding in late summer produces soft growth that is disproportionately vulnerable to frost damage, which undoes the preparation you put in elsewhere.

When is the best time to repot a plant in a container?

Spring — March to early May — is the ideal window. Plants are coming into active growth, roots re-establish quickly in fresh compost, and the whole growing season lies ahead for recovery. Avoid repotting in autumn or mid-winter when growth has slowed and the plant has little energy to adapt to a new root environment.

Whether you are starting your first container display or refreshing an established entrance, our shaped evergreens and architectural plants arrive ready for potting in generous root balls. Browse the full range in Architectural Collections and Entrance Bundles. Delivered free to your door.