At a glance
The first thing an indoor garden needs is honest light. Not “good light” in the estate agent sense, not “bright enough to read in,” not the kind of light a room has when every window faces roughly south-ish and the sun occasionally makes an appearance. The actual measured light falling on the actual surface where you plan to grow things. Everything else follows from that one number, and the reason most indoor growing fails in UK homes is that people skip this assessment and go straight to buying plants.
A houseplant collection, a windowsill herb garden, a tray of microgreens, salad leaves in pots: all of these are achievable in a British home with no outdoor space and no specialist equipment. Which of them are achievable in your specific home depends on your windows. Get that right first and the rest is sensible decisions. Ignore it and you will wonder for years why your basil keeps dying and the peace lily in the corner never flowers.
Light: the only thing that actually matters first
UK homes are darker than most people realise, particularly from October through to March. A living room 2-3 metres from a south-facing window in winter gets roughly 500-2000 lux of light: enough for low to medium-light houseplants, not enough for herbs that want full sun. A north-facing room in January gets even less. Plants that thrived all summer on the same windowsill can slowly decline from October onwards not because anything changed in how you care for them, but because the available light halved.
Distance from the window matters almost as much as the direction it faces. A plant 50cm from a south-facing window receives substantially more light than the same plant 2 metres back in the same room. The difference can be a factor of four to ten. Before buying anything, do the hand shadow test: hold your hand 30cm above a white surface in the spot where you plan to grow. Sharp defined shadow means bright light. Faint shadow means medium light. No discernible shadow means low light, and in low light your options are genuinely limited.
The other thing UK growers have to reckon with is central heating. In winter, heating drops indoor humidity from the 50-60% that most tropical houseplants prefer to 30-40%. Brown leaf tips that appear through the winter months are usually this: not overwatering, not underwatering, just dry air. Bathrooms and kitchens are naturally more humid, which is why moisture-loving plants tend to do better there.
Grow lights: when natural light is not enough
A regular desk lamp or ceiling light does not help plants grow. This surprises people, but ordinary bulbs do not produce the right spectrum or intensity for photosynthesis. What does work are full-spectrum LED grow lights, which are now widely available, relatively cheap and much more energy-efficient than older fluorescent systems.
A grow light added to a north-facing windowsill herbs can turn a space where herbs just about survive into one where they actually produce. I added a clip-on grow light to my herb shelf two winters ago after watching my parsley produce about one usable leaf per fortnight in January, and the difference was immediate enough to be embarrassing in retrospect.
Leggy pale growth reaching upward means the light is too far away. Brown crispy patches on leaves mean it is too close. Plants need darkness too. A timer is not optional.
The houseplant collection
The number one cause of houseplant death in UK homes is not neglect. It is overwatering. More plants meet their end from soggy compost and rotted roots than from being forgotten about. The signs are often misread: a wilting houseplant usually prompts more watering, but a plant wilting in wet compost is drowning, not thirsty.
The reliable method is to push a finger 2-3cm into the compost before every watering. If it is still moist at that depth, put the watering can down and come back in a few days. If it is dry, water thoroughly until it drains from the bottom and do not water again until it dries out. In summer this might be every few days for some plants. In winter it might be every two to three weeks. The pot, the plant, the room temperature, the compost mix and the season all affect this. The only constant is checking before watering.
Winter is the period most houseplants are killed by their owners. Growth slows or stops, which means the plant is using almost no water, which means the compost stays wet far longer than it did in summer. Continue summer watering habits through October to February and you will drown them.
None of these are exciting but all of them survive the conditions most UK homes actually provide rather than the ones people imagine they provide. Once you have a feel for watering and light levels, the more demanding plants become manageable. Monstera needs medium to bright indirect light and consistent watering. Calathea and Maranta need humidity and filtered water. Hard tap water causes brown leaf tips. Fiddle leaf fig is difficult: it drops leaves when moved, when the light changes, when you look at it wrong. Begin with the reliable ones.
Windowsill herbs
Herbs on a kitchen windowsill look easy and often are not, and the reason is almost always light. The herbs that need full sun (basil, rosemary, thyme, oregano) are the ones people most want to grow indoors, and they are the ones most likely to fail on anything except a south-facing windowsill. Basil in particular is unforgiving: below about 10 degrees it sulks, below 6 hours of direct daily sun it produces leggy stems and sparse leaf. I have killed enough indoor basil to know that a bright south-facing sill in summer is fine and anything else is an exercise in disappointment unless you supplement with a grow light.
Mint must always be in its own pot. Planted alongside anything else, it colonises the entire container within a few weeks. Rotate your pots every few days so all sides get equal light exposure. Never buy a supermarket herb and try to keep it going as-is. Those pots contain several seedlings compressed into a volume of compost designed for kitchen use over a week, not ongoing production. Either split them into individual pots with fresh compost when you get home, or accept them as a one-week supply and grow long-term plants from seed. Take no more than a third of the plant at any one time: cut regularly and you get a bushy productive herb; take more than that and you get a damaged plant that takes weeks to recover.
Microgreens: the indoor growing shortcut
If there is one indoor growing activity worth recommending to anyone with any amount of window space, it is microgreens. Seed to harvest in 7-21 days depending on the variety. No outdoor space, no specialist equipment beyond a shallow tray. Cost of entry under ten pounds. Year-round regardless of season.
Microgreens are seedlings harvested young, before the plant develops beyond the seed leaves and first true leaves. They have concentrated flavour and nutritional content compared to the mature plant. Fill a shallow tray with 3-4cm of seed compost or coir, water it, then sow seeds thickly, much denser than you would sow outdoors, because these are harvested long before they compete for space. Cover with another tray for the first three to five days for darkness and warmth, uncover when shoots are 2-3cm tall, place on a bright windowsill, and mist daily. Harvest with scissors just above soil level when the first true leaves appear.
The soil cannot be reused for the same crop. Cut the microgreens, compost the root mat, start a new tray. A rotation of two or three trays at different stages means a weekly supply of fresh greens with almost no effort.
Salad leaves indoors
Loose-leaf lettuce, rocket, baby spinach, mizuna and mustard leaves all grow well in pots on a bright windowsill without specialist equipment. Shallow pots work fine. 15-20cm deep is enough. Cut-and-come-again varieties are what you want: harvest the outer leaves and the plant regrows from the centre. Iceberg and head lettuce types do not work well indoors: they take too long, produce too little and need more light than most UK windowsills provide in winter. In winter even a south-facing sill may produce slow, leggy growth because the light hours are short. A supplemental grow light on a timer is the single most cost-effective improvement for any indoor edible setup.
Containers, compost and feeding
Do not use garden soil inside the house. It compacts badly in pots, drains poorly, weighs more than it should, and introduces pests and pathogens that thrive in warm indoor conditions. Use proper houseplant compost for decorative plants, and seed or general-purpose peat-free compost for herbs and edibles.
Every container needs drainage holes. Saucers underneath protect surfaces and let excess water drain away, but empty them after watering rather than leaving water sitting under the pot. A saucer full of standing water is root rot building slowly from below. When repotting houseplants, do not jump to a much larger container thinking more space is better. A plant in a pot significantly larger than its root ball sits in compost that retains moisture it cannot use, and root rot follows. Move one pot size up and no more, in spring when the plant is actively growing.
Problems
Most indoor growing problems come back to light or water. Sort those two things and the list below becomes much shorter.
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