Plant Doctor Archive

Unhappy hydrangeas

MY wife and I have a large hydrangea which used to flower well. For the last two years it hasn't flowered at all. We feed it and cut it back but still no flowers. Secondly, we have potted geraniums with leaves that turn yellow and drop off, again we have fed and sprayed them. Any ideas?

YOU can usually rely on hydrangeas to flower each year with little trouble. It could be because you've been cutting the plant back.

The best time to prune the common hydrangea (Hydrangea macrophylla) is in late winter. Cut out any dead, weak or thin shoots close to the base of the plant. Of the strong healthy ones that are left, look for those that flowered last year - they'll probably still have old dead flowerheads at their tips. Prune these back to a pair of the fattest buds you can find close to the top of the shoot. Don't cut them back too hard or you may get no flowers the next summer. You should still have some shoots left uncut - those that didn't flower at all last year. Leave them well alone as they'll produce the new season's first flowers - if you cut them back they simply won't flower.

Yellowing and dropping of geranium leaves can be caused by any one of a variety of problems, including rust, leaf spot, root disease or lack of nutrients.

To encourage healthy growth, repot your plants each spring or early summer using a good quality general potting mix. Cut the top growth back by at least half and prune the root system when repotting.

Feed them regularly during the growing season and, if any spotting occurs on the leaves, spray with a fungicide such as Bravo or fungus and mildew spray. Give them plenty of light and fresh air and don't keep the mix constantly wet - allow it to dry out somewhat between waterings.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.