Plants for the hottest window

Full sun indoors means direct sunlight falling on the leaves for four hours or more. That is the brightest window in the house with nothing in front of it, and it depends on which side of the equator you live. North of it, the window is the south-facing one. South of it, the window is the north-facing one. A west window also gets direct sun, in the hotter and harsher afternoon, in both hemispheres.

Very few houseplants want this. The ones that do are mostly succulents, along with a few herbs, and a jade plant is happy on a sill that would scorch almost anything else. The rest of the house holds plants that would burn there, so the sill needs a tenant chosen for it, not the plant that happened to be left over.

The mistake that kills them

Treating the hot sill as one condition when it is three. The first is light, which these plants want in quantity. The second is heat, because glass concentrates the sun. The third is water, and it is the one that kills them. A pot on a hot sill dries fast, which tempts a daily drink, and a sun-loving succulent wants the compost dry most of the way down before it gets any. Meanwhile a herb on the same sill may want a drink every few days. The entries give each plant’s own interval, and on one sill those can differ several times over. The guide to telling whether a plant needs water shows how to check by finger and by weight.

The second mistake is in the season. The sun is lower and weaker in winter and the days are short, so the same sill is a different place in July and in January, and a plant that spent the winter in a dim room will scorch in the first strong sun of spring. Even a jade plant burns after a winter indoors. Bring plants to the glass gradually, as the guide to moving plants between seasons sets out for the move outdoors, and keep leaves from pressing against the pane. Turn the pot a quarter turn each week so the plant does not lean.

How the list was chosen

An entry is listed here when it is recorded at the brightest light level, when it can live indoors, when it is tagged for a windowsill, and once it has been reviewed. The tag keeps the list to plants that fit on a sill, so the larger sun lovers, which stand on the floor beside the window, are not here. The list is sorted with the easiest first, then by name.

The succulents and cacti shelf is wider, and gathers every succulent in the journal whatever the size. If a plant here starts to stretch, fade or lean, it is asking for more light, and a move to a brighter window is more likely to help than any change to the watering.