To plant garden tubs, add drainage, use peat-free mix, set by sun needs, water deeply, and feed on a steady schedule.
Big, roomy tubs grow lush food and flowers with less bending and less weeding. The trick is treating the tub like a mini bed: right size, free-draining base, quality mix, matched plants, and steady care. This guide walks you through setup, planting, and upkeep with clear steps and real-world tips that save time and wasted soil.
Garden Tub Basics: Size, Drainage, And Mix
Start with a container that’s wide and deep enough for the roots you plan to grow. Drill or confirm multiple holes in the base, keep them clear, and raise the tub slightly so water can escape. Skip garden soil; use a fresh, peat-free potting blend built for containers. These mixes stay airy, drain well, and hold moisture without turning heavy.
Pick The Right Container Material
Plastic, resin, wood, fiberglass, and galvanized stock tanks all work. Metal warms fast in spring and cools quicker on cold nights, so monitor moisture. If you’re using a stock tank, drill several 10–12 mm holes across the base. Don’t block them with trays or tight bricks.
Drainage Myths To Leave Behind
No rocks at the bottom. They create a perched water layer that keeps roots soggy. Use uniform potting mix from top to base. Elevate the tub on feet or pavers so runoff can leave freely.
Soil Mix That Performs
Choose a peat-free blend with ingredients like coir, bark, composted wood fiber, and perlite or grit for structure. If your mix has slow-release fertilizer, it feeds for the first two months; after that, plan a feeding routine. For sustainability and plant health, see the Royal Horticultural Society’s guidance on peat-free compost choices.
Tub Sizing And What Fits (Quick Planner)
Use this planner to match tub size to plant types. Depth helps keep roots cool and moisture steady.
| Tub Size (Dia/Depth) | What Grows Well | Notes |
|---|---|---|
| 30–40 cm / 25–30 cm | Herbs, salad leaves, radish | Lightweight; dries fast; water often in heat |
| 45–50 cm / 30–35 cm | Basil bushes, peppers, dwarf tomatoes | One main crop per tub for best yield |
| 60–70 cm / 35–40 cm | Tomatoes, aubergine, compact courgette | Stake or cage at planting time |
| 80–100 cm / 40–45 cm | Mixed flowers, shrub rose, small fruit bush | Heavier; add wheels or place before filling |
| Stock tank 120–150 cm / 45–60 cm | Tomato trio, climbing beans, pollinator mix | Drill many holes; mulch to cut watering |
How To Plant A Garden Tub: Step-By-Step
1) Set The Tub And Plan Sun
Six to eight hours of direct sun suits most fruiting crops. Leafy greens and many flowers thrive with four to six hours and a bit of shade in hot spells. Place tubs where a hose reaches and wind isn’t funneled.
2) Create A Free-Draining Base
Drill several evenly spaced holes. Lay mesh or a single sheet of landscape fabric inside only if pests come up through the base; it’s optional and can slow drainage if doubled. Lift the tub on feet so runoff clears the surface underneath.
3) Fill With Fresh Potting Mix
Pour mix to the rim, then settle it by tapping the sides. Top off, leaving 2–3 cm headspace for watering. Mix in a slow-release fertilizer if your bag doesn’t include one. Avoid compacting the surface; you want air pockets for roots.
4) Set Plants Or Sow Seed
Space transplants so mature leaves will just touch. Bury tomato stems slightly deeper than they sat in the pot; keep peppers and aubergines at the same depth as the nursery pot. Water seedlings in gently to remove air gaps.
5) Stake, Cage, Or Trellis Right Away
Insert supports before roots spread. Tie with soft ties that won’t cut stems. A simple cane tripod or a mesh panel gives vines a clean climb.
6) Water Deeply
Soak until you see steady drips from the base. Shallow sprinkles lead to weak roots. Morning watering is ideal; it reduces leaf wetness time and disease risk. For science-backed watering and feeding rhythm, see the University of Minnesota’s guide on fertilizing and watering container plants.
7) Mulch The Surface
Add 2–3 cm of fine bark, straw, or cocoa hulls. Mulch buffers heat, slows evaporation, and keeps potting mix from crusting.
Plant Matching: Easy Combinations That Work
Mix plants with the same thirst and light needs. Pair shallow-rooted herbs with leafy salad greens. Keep heavy drinkers—tomatoes, courgettes, cucumbers—in their own roomier tubs so you can water and feed as they demand.
Sunny, Warm Spots
- Tomato with basil and trailing thyme (large tub)
- Chilli with dwarf marigold and chives (medium tub)
- Aubergine with compact nasturtium as a living mulch
Morning Sun, Afternoon Shade
- Loose-leaf lettuce blend with parsley
- Spinach with spring onion
- Fuchsia and begonias for color without scorch
Fragrant Herb Tubs
- Rosemary (own tub), or with lavender in a wide, free-draining mix
- Mint (own tub with root barrier)
- Oregano, thyme, and sage together in a shallow, sunny tub
Watering, Feeding, And Routine Care
Container roots live in a small volume, so moisture and nutrients swing faster than in ground beds. A simple routine keeps plants even and productive.
Watering Rhythm
Check daily in summer. If the top 2–3 cm feel dry, water until runoff. In heat waves, big tubs may need a second soak in late afternoon. Group tubs to make watering faster and to raise local humidity a touch.
Feeding Plan
Use the starter charge in your mix, then shift to a balanced liquid feed every 7–14 days during active growth, or rely on a slow-release prill refreshed midseason. Fruiting crops respond well to steady nutrition; leafy tubs can get by with a gentler schedule.
Prune, Deadhead, And Clean
Pinch tomato side shoots on cordon types, remove yellowing leaves near the soil, and snip spent flowers to push new blooms. A monthly flush with plain water helps prevent salt buildup from fertilizers.
Safe Use Of Galvanized Or Metal Tubs
Galvanized planters are common and widely used for edibles. The zinc coating is stable in neutral potting mixes, drainage is the real driver of plant health, and good airflow keeps the container shell cooler. If heat is intense, shade the west side of the tub or mulch heavily to protect roots.
What To Plant By Season
Spring Starts
Salad greens, peas on a short trellis, radishes, beets, calendula, pansies. Sow little and often to keep harvests coming.
Summer Staples
Tomatoes, peppers, basil, bush beans, dwarf cucumbers, zinnias, petunias. Give fruiting crops full sun and steady feed.
Autumn Refresh
Switch back to cool-season greens, chard, Asian greens, violas, and mums. Shorter days mean fewer waterings; watch for overwatering.
Spacing And Depth Cheatsheet
Use this chart to set plants without crowding. Crowding means mildew and fewer fruits.
| Crop / Plant | Minimum Depth | Spacing In Tub |
|---|---|---|
| Tomato (indeterminate) | 40–45 cm | 1 plant in 50–60 cm tub |
| Tomato (bush) | 35–40 cm | 1 plant in 45–50 cm tub |
| Pepper / Aubergine | 30–35 cm | 1 plant in 40–45 cm tub |
| Courgette (compact) | 40–45 cm | 1 plant in 60–70 cm tub |
| Bush beans | 25–30 cm | 6–8 plants in 60 cm tub |
| Leaf lettuce | 20–25 cm | 10–12 plants in 45–50 cm tub |
| Basil (large) | 25–30 cm | 2–3 plants in 45–50 cm tub |
| Strawberry | 25–30 cm | 4–6 plants in 50–60 cm tub |
| Dwarf dahlia | 30–35 cm | 3 tubers in 50–60 cm tub |
Common Mistakes And Easy Fixes
Using Garden Soil
Garden soil compacts, drains poorly in tubs, and can bring pests. Stick to potting mixes designed for containers.
Too Few Drainage Holes
One tiny hole isn’t enough, especially in big tubs. Drill several and keep them clear of paving and leaves. Raise the container on feet so the holes aren’t blocked.
Watering Little And Often
That leaves the root zone dry below. Water until excess runs out, then wait until the top layer dries again. Add mulch to stretch the interval.
Packing Mixed Sun Plants Together
Sun lovers and shade lovers share poorly. Group by light needs so you’re not over- or under-watering half the tub.
Stock Tank Setup: Quick Notes
Use a step bit to drill holes across the base, 10–12 mm wide, spaced every 10–12 cm. Line edges with rubber trim if sharp. Fill only with potting mix. If heat bakes the tank, slide a cardboard sleeve or foam board between tank and sun-facing wall to cut radian heat. Mulch thickly and water deeply.
Simple Planting Recipes For Tubs
Salsa Tub
One bush tomato, one chilli, three basil plants, and a ring of spring onions. Stake the tomato and chilli at planting. Feed weekly once fruit sets.
Pollinator Party
Calendula, dwarf cosmos, alyssum, and a trailing thyme edge. Deadhead weekly to keep blooms rolling.
Cut-And-Come-Again Greens
Loose-leaf lettuce sown in bands with spinach and mizuna. Harvest outer leaves often and resow a small strip every two weeks.
Care Calendar: Month-By-Month (Adjust For Climate)
Early Spring
Set tubs, drill holes, clean, and refill with fresh mix. Sow hardy greens and peas. Add a light slow-release feed at setup.
Late Spring
Plant warm-season crops after frost. Install stakes and cages now. Start a weekly liquid feed for fruiting crops two weeks after planting.
Summer
Water daily in heat. Mulch deeper if the surface dries too fast. Side-dress long-season tubs with a small top-up of slow-release prills.
Autumn
Swap to cool-season greens and flowers. Reduce watering as days shorten. Check drainage holes aren’t clogged by falling leaves.
Winter
In frost-prone areas, wrap tubs with burlap or bubble wrap, or move them close to a wall. Empty cracked mixes and store clean and dry.
Quick Reference: Watering And Feeding Signals
- Wilting at midday that recovers by evening: raise mulch or water earlier.
- Leaf edges crisping: tub is running too dry between waterings; soak fully.
- Yellowing and slow growth midseason: resume balanced feed or refresh slow-release.
- White crust on the surface: flush with plain water to clear salts.
Why This Setup Works
Free drainage, fresh potting mix, matched plant needs, and consistent care let roots breathe and drink without stress. That combo shortens time to harvest, keeps flowers cycling, and makes watering simpler. Place tubs where you’ll see them daily, and the routine becomes easy: quick check, deep water, and a little feed on schedule.
Helpful Sources
For peat-free mix guidance, see the RHS page linked above. For watering and feeding rhythm in containers, the University of Minnesota’s article linked earlier lays out clear, research-based steps that match what works in tubs.