If you've read the first half of this, you've spent a couple of weeks watching: which plants moved first, which pots started drying faster, where the light is landing that it wasn't a month ago. This is the second half — what to actually do about it.

The short version: spring changes four things for an indoor plant, and they arrive in a particular order. Light comes back first. Water follows, because the plant is using more of it. The mix gets read, not replaced. Feed comes last, once there's growth to feed. Most spring advice runs that list backwards — starts at the fertiliser and the new pot — and that's where the trouble comes from.

One thing before the list. "Growing season" is a useful shorthand, not a law. Plenty of indoor plants in bright, warm homes never really stop over winter, and plenty in dim ones won't wake up on the first of September just because the calendar did. Everything below is triggered by what the plant is doing, not by the date.

Light: check where it lands now

The days are getting longer and the sun is getting stronger, but that doesn't mean every spot in the room is getting brighter. Winter sun sits low and reaches deep into the house. As the sun climbs through spring, that patch of direct light pulls back towards the window.

So the plant that was getting plenty of light a few metres back in July might need to move closer now — and the plant that's already at the window is about to get more direct sun than it's had in months. Leaves that grew through winter are softer than the ones that grew last summer, and the spring sun strengthens quickly, so any move towards stronger light happens over a couple of weeks, not an afternoon. Scorched patches in September are usually this: the right spot, reached too fast.

Before you assume last summer's spot is still the right one, check the light where the plant actually sits. The Shadow Test is the quickest way: hold your hand about ten centimetres above a leaf during the brightest part of the day for that spot and look at the shadow. A distinct shadow means light the plant can use; a faint one means lower light; barely any shadow at all means the plant is running close to the bottom of its range. You're not looking for direct sun, and the edges of the shadow don't matter — you're checking whether enough light reaches the leaf to cast a visible shadow at all.

The lean you noticed over the last fortnight is the plant's own version of this test. A plant that's tilted hard towards the window has told you the light in that spot has changed. Turn it a quarter each time you water, and it'll grow even again.

Water: the dry-back shortens, so recalibrate

More light and warmer mix mean roots that are drinking again. The gap between waterings closes — not because you've decided it should, but because the pot gets light faster. If you've been reading pot weight through winter, you've already felt it happen.

What changes is the rhythm, not the method. Keep letting each plant dry back as far as it likes between waterings; just expect to get there sooner. If your reference weight has drifted over winter, reset it now: water thoroughly, let the pot drain, then lift it. That's full. Everything lighter than that is the plant telling you how far it's dried down. There's a full walk-through in the dos and don'ts of watering.

The trap in spring is the opposite of the winter one. In June the risk was watering a plant that wasn't using it. In September the risk is assuming the winter rhythm still holds and letting a plant that's actively growing sit dry for a week longer than it wanted. Wilting on a plant that's just pushed a new leaf is often that.

Mix: read it before you replace it

This is the season everyone gets told to repot everything. Most plants don't need it. Some are root-bound and want a size up; plenty just need the top few centimetres refreshed; a lot need nothing at all. The difference is in the mix, not the date — so run the Finger Probe Test before you reach for a new pot. Loose and crumbling apart rather than packed into a dense mass means the structure is still working. It's one good sign, not the whole diagnosis — a root-bound plant can be sitting in perfectly good mix — but a plant whose mix is still working doesn't need disturbing just because it's spring.

We've covered the decision properly — potting up versus refreshing, and how to tell which one your plant is asking for — in repotting indoor plants in spring. The line that matters from it: spring is the window, not the reason. If the plant needs repotting, spring is a good time to do it. If it doesn't, spring isn't an argument.

Feed: once there's growth to feed

Feed comes last on purpose. Fertiliser doesn't start growth; it supports growth that's already happening. A plant with one tentative new tip can't use much. So the trigger for stepping the feed back up isn't the season — it's clearly active growth: new leaves coming through, and a pot that's drying noticeably faster.

When you're there, keep it simple: feed in the watering, at the rate on the label, every second time you water. Tying it to the watering rhythm means the feed scales with the plant automatically — a plant that's drinking more gets fed more, and one that slows down gets less, without you having to think about it.

If you kept a light feed going through winter, hold it there until the growth is obvious, then step up. If you stopped altogether, start again at the rate on the label rather than trying to catch up.

What to leave alone

• The feeding calendar. There isn't one. Growth sets the pace, and the watering rhythm carries the feed. If a plant isn't moving, more fertiliser won't move it.
• Every pot, all at once. Repot the plants that need it. The rest will grow just fine in mix that's still working.
• The big move. Stronger light in stages. The window will still be there in three weeks.
• The full haircut. Prune what's dead now, shape as the growth comes through.