Gadenin日本語Get the appThe shape of the year
The geranium year has two halves, and the second one is the part most people never see. From late spring to the first frost the plant grows and flowers hard outdoors. From the first frost to the following spring it should be kept cold, dark enough, and above all dry, doing almost nothing. The plant is not an annual; it is a tender perennial being treated as one.
The four decisions that shape the year are when you bring plants in, how ruthlessly you cut them back, how little you water them through winter, and when you start them again in late winter. Everything else follows from those.
Work from your own first and last frost dates rather than from months, and the same plan reads correctly in either hemisphere.
| Point in the year | Main job | The judgement to make |
|---|---|---|
| Late winter | Start plants back into growth, water lightly | Wait for lengthening light, not warmth alone |
| Early spring | Repot, cut back, take cuttings | Move up only one pot size; keep them snug |
| Mid spring | Grow on frost free, pinch young plants | Pinch once at five or six leaves for branching |
| After the last frost, nights above 50F (10C) | Harden off and plant out | Cold nights stall the plant; waiting costs nothing |
| Early summer | First flowers, start removing spent stalks | Snap each stalk off whole at its base |
| Midsummer | Water by weight, feed containers lightly | Nothing high in nitrogen; dry between waterings |
| Late summer | Take cuttings, cut leggy plants back a third | Root them while there is still warmth and light |
| Before the first frost | Lift and bring plants under cover | One frost through the stems is enough to kill them |
| Winter | Keep cool, bright and nearly dry | Water only when leaves start to shrivel |
Bringing plants in before the first frost
Do this before frost touches them, not after. Geranium stems are full of water and a single hard frost bursts them, after which the plant collapses to slime within days. Watch the forecast in autumn and act on the first night predicted below about 37F (3C).
Lift plants from the ground with a fork, shake most of the soil off the roots, and cut the top growth back hard, by about half, removing every flower, bud, yellow leaf and spent stalk as you go. Anything soft or dying that goes into storage with the plant becomes gray mold by midwinter. Pot the trimmed plants into the smallest pots that will hold their roots, using free draining compost, and water once, lightly.
Plants already in pots need the same cut back and tidy but not repotting. Check every one for vine weevil grubs before it comes in, and hose the undersides of the leaves to knock off whitefly, or you will be nursing an infestation in a warm room all winter.
- Cut back by half and strip the plant clean Remove all flowers, buds, yellow leaves and stalk stubs. A bare stubby plant stores far better than a full leafy one and regrows perfectly well in spring.
- Pot small and gritty Trim the roots if you must to fit a small pot. Restricted roots in free draining compost stay dry, and dry roots are what survive winter.
- Water once, then leave for a fortnight One light watering settles the compost after repotting. After that give nothing at all for two weeks while the plant adjusts to being under cover.
- Check for pests before it comes inside Look under the leaves for whitefly and tip the pot out to check for white grubs in the compost. Both multiply unchecked in a warm winter room.
Winter: cool, bright and nearly dry
The winter target is a plant that is alive but doing almost nothing. Aim for 45 to 55F (7 to 13C) with as much light as you can give it. A frost free greenhouse, an unheated porch, a cool spare bedroom or a bright garage window all work. A warm living room is the worst place, because warmth without light makes long pale weak growth that collapses in spring.
Water far less than feels comfortable. Once every three or four weeks is typical, and only enough to dampen the compost rather than soak it. The right signal to water is the leaves beginning to go slightly limp or the lowest ones starting to shrivel. A geranium that is a bit too dry recovers in a day; one kept damp all winter rots at the base and cannot be saved.
Give no feed at all between autumn and late winter. Pick off yellowing leaves whenever you pass, ventilate on every day that is not freezing, and expect the plant to look shabby. It is supposed to. A stubby stem with a few tired leaves in midwinter is exactly right.
The bare root method also works if space is short: shake the soil off, hang the plants upside down in a cool dark frost free place, and soak the roots for an hour every few weeks. It looks alarming and the survival rate is lower, but plants that come through it grow away strongly.
Waking plants up in late winter
As the days visibly lengthen, start the plants moving again. Increase watering gradually to normal, move them into the best light you have, and raise the temperature if you can. Within two or three weeks new shoots break from the old stems, usually low down where you cut in autumn.
Once growth is clearly under way, cut each stem back to a strong new shoot to shape the plant, and repot into fresh gritty potting mix, going up only one pot size or simply refreshing the compost in the same pot. Start feeding at half strength once new leaves are expanding. Every piece you cut off is a free cutting, and spring cuttings root in two to three weeks and flower the same summer.
Then harden off and plant out only once nights are reliably above 50F (10C). An overwintered plant put out into cold nights sulks for a month and undoes the whole winter's work.
Keep a short record each year: the date you brought plants in, how often you watered through winter, how many survived, and the date they broke into growth. Two winters of that record will tell you far more about your own conditions than any general advice.