When it stops raining
Dry spells
Who gets the hose first when it's been dry for a fortnight. 7 plants genuinely need it; the rest range from "if there's time" to "please don't".
Water these first7
Thin leaves, shallow roots or a lot of flower to support. These are the ones that suffer first and show it fastest.
- Border phloxThe mildew that arrives in August is the bill for a dry fortnight in July, so keep the water going once it is in flower rather than stopping when the heads open. Bare soil around a phlox bakes within days — if the spring mulch has thinned, put more on before you water, not after.
- Canna lilyThis is the one plant here you cannot overwater in a heatwave; stand a pot in a tray of water and leave it there. Dry at the roots and the rolled new leaves open ragged and half-sized, and the flower stems come up short — neither recovers, you just wait for the next shoot.
- Cherry tomatoThe first plant to suffer in a heatwave and the least forgiving about it. A pot left to dry out completely will drop its open flowers, and any fruit already swelling will rot at the base whatever you do afterwards. Water in the evening, into the soil rather than over the leaves, and mulch the surface.
- DahliaA dry week while it is in bud gets paid a fortnight later in buds that brown and drop without opening, and catching up afterwards brings none of them back. Two full cans at the base twice a week through a heatwave, in the evening, and keep a mulch over the tubers so they are not sitting in soil that bakes.
- Double daylilyIn real heat the flowers crumple by lunchtime instead of lasting the day, which looks alarming and is not worth watering over. The watering that decides the display happened weeks earlier while the flower stems were forming, so by the time an August heatwave arrives this one can go to the back of the queue.
- Japanese mapleScorched leaf margins are permanent for the season, so the watering that counts is the one done before a hot windy week rather than after it. Water the full spread of the canopy rather than the base of the trunk, and keep the mulch topped up — the fine surface roots dry out first and a bare, baked root zone does the damage on its own.
- Lacecap hydrangeaJudge it first thing in the morning rather than mid-afternoon — a plant still flat at 7am has genuinely run dry, and it then wants a full 10 litres poured slowly over the whole spread of the canopy, not a splash at the stems. The roots are shallow and wide, so keep the mulch topped up and the soil under it covered.
Then these, if there's time8
A deep soak every few days in a long dry spell. They will survive without it, but they won't look their best.
- Climbing roseThe ground at the foot of a fence is the driest in the garden — the fence throws a rain shadow and the roots are sharing it with the posts — so it needs more water than the free-standing roses despite asking for it less obviously. Put the can an arm's length out from the stems rather than straight down the middle.
- HollyhockA dry spell strips the lower leaves before the top of the spike has opened, which makes the rust look far worse than it is. The plants actually at risk are the first-year rosettes — one that dries out in its first summer never makes a spike at all, whereas an established plant already in flower is mostly a cosmetic problem.
- Japanese snowball viburnumNext spring's flower buds are being formed through this summer's heat, so a long dry spell now shows up as a thin display next May rather than as anything visible at the time. Water it before the margins crisp rather than after — the browning is a record of something that has already happened and it stays on the leaf all season.
- Morning gloryIn a container it will dry through in a day in real heat and the flower buds are the first thing it drops. Water in the evening and mulch the surface. In open ground it is far tougher than it looks and can be left to get on with it.
- Pale pink shrub roseDrought is what makes a repeat-flowering rose stop repeating — it shuts down quietly and the second flush simply never arrives, with no visible damage to warn you. If it is only a season or two in the ground, treat it as high priority instead, because a rose that has not yet got its roots down cannot go and find its own water.
- PenstemonIt flowers through a dry spell without much complaint, and keeping up with the deadheading does more for it than the hose will. If you do water, put it on the soil around the clump rather than into the middle of it — a crown kept wet in warm weather is how the woody base goes soft.
- Shrub roseLeaves that yellow and drop in a hot August are as often drought as black spot, so check whether the ones on the ground are actually marked before assuming the worst. Mulch earns more here than extra watering — bare soil round the base dries to a spade's depth inside a week of real heat.
- Shrubby salviaIt is a Mexican plant and built for this, so the heatwave symptom is a pause rather than a decline — flowering stops and the small leaves go dull and start dropping. One good soak and a light trim of the spent spikes restarts it within a fortnight; do not let that turn into a habit of regular watering, because it flowers better kept lean and dry.
Leave these alone5
Drought-adapted and established. Watering them is usually counterproductive — soft growth, floppy stems, and rot in the ones that want sharp drainage.
- Bear's breechesLeave it alone. The roots go down well over a metre and reach water nothing else in the border can, and the worst a heatwave does is scorch a few lower leaves and make it look shabby until the fresh autumn flush. Watering and feeding it in a dry spell buys nothing but soft, floppy foliage and mildew.
- Hardy geraniumThe right answer to a scorched, collapsing mound in August is the shears rather than the hose — cut it back hard, leave it, and it makes a complete set of clean new leaves once the rain returns. Watering a tired clump only draws out the tatty stage.
- Rose campionThe silver felt on the leaves is its own sun protection, and a plant that gets watered loses it — greener, softer, floppier, and far more likely to rot at the base. Leave it off the watering round altogether. The single exception is a seedling moved in spring, which wants a couple of soaks to take and nothing at all after that.
- Wild roseIn a dry summer it sheds its lower leaves early and sets a smaller crop of hips, and both are the plant managing itself rather than anything to correct. It is a hedgerow shrub with a hedgerow root system, and there is genuinely no job to do here.
- YarrowThis is the weather it was built for, and it will be standing up straight while everything around it sulks. Skip it on the watering round entirely — and if the clump is already lying open, cut it back hard now rather than soaking it, because water and rich ground are what made it flop in the first place.
Indoors, in a hot room8
Unaffected by the weather, affected by the room. Compost dries out faster in summer, and dry air near a sunny window is a separate problem from dry compost.
- AnthuriumDry air hurts it faster than dry compost. Brown crisp margins and new leaves that come out small and stall are humidity, not thirst, and watering harder in response makes the root problem worse. Stand it on a tray of damp gravel in a hot spell and keep it out of the path of any fan.
- Chinese money plantA drooping pilea is a nuisance rather than an emergency and it will come back from a proper soak. What it does not come back from is a fortnight of the stem being wet at soil level, so in hot weather water it more often but no more heavily, and never leave it standing in a full saucer to cope while you are away.
- Christmas cactusSegments that have gone soft and creased are thirsty; segments that are soft at the base and darkening are not. In a hot room check it weekly rather than monthly, and if it dries out badly water it in stages over a couple of days rather than flooding a shrunken rootball at once.
- Heartleaf philodendronOne of the last things in the house to need attention in a hot spell. Trailing stems dry faster than the pot suggests because they are all leaf and no reservoir, so check the compost rather than reading the droop, and do not repot into something bigger to fix it.
- MonsteraIn a hot room the compost can dry through in half the usual time, so check it with a finger a couple of times a week in a heatwave rather than watering to a schedule. Brown crisp edges and new leaves that stall half-open are dry air though, not dry compost — move it back from a sun-baked window instead of reaching for the can.
- PalmBrown, crisp leaflet tips are almost always dry air or hard tap water rather than dry compost, and watering harder in response is how a tip problem becomes a root problem. In a hot spell check with a finger, move it out of any draught from a fan or an open door, and if the tips keep browning try rainwater or filtered water for a few months.
- Rubber plantA hot room dries the pot through faster than a cool one, so check with a finger weekly in summer instead of holding to a fixed interval. Crisping leaf edges are dry air rather than dry compost, and the fix for those is moving it back from sun-baked glass, not more water.
- White princess philodendronThe white parts of each leaf go crisp and brown at the edges first, and once they have they stay that way. In a hot spell that is usually dry air rather than dry compost, so check with a finger before watering and move it away from any sunlit glass, which scorches white tissue in an afternoon.