A new broom?
I have a broom bush, planted in a crowded site against an east-facing fence. It is quite straggly and I would like to reduce it in size. This year it flowered poorly having done well in previous years. It is about four years old. Should I prune it now, or have I left it too late? If I do cut it back, what will it do in the future?
Stuart Bliss, via email
Your picture showed a lopsided shrub (Cytisus x praecox, I think) with a mass of dead twiggy shoots at its base, not exactly a thing of beauty.
The sad fact is that, at four years old and without any regular grooming, your broom has probably had its day. These are short-lived shrubs, making up for it in the wild by seeding around freely. If you can spare just a little more space, replace it this autumn with another. This time, however, take the shears to it immediately after flowering each year, cutting back about half the greenery. It will look like a green hedgehog for a week or three, but will soon bush out and flower along the length of the young drooping branches the following year. As it gains stature, remove dead shoots from the base and stake the emerging “trunk”. Treated thus, this broom will last an extra year or two and look more attractive too.
Some of the leaves of my astrantias have small, dark-brown specks and brown patchy blisters on them. What is causing this? Will it kill my plants and how can I cure it/stop them?
Bridget Farmer, via email
The small dots are made by the mouth parts of a tiny fly, Phytomyza astrantiae (astrantia leaf miner) that then lays eggs on the leaves which hatch out into tiny larvae that feed within the leaf tissue, causing the irregular brown patches. This leaf-mining fly is specific to astrantia, and two generations are produced each summer. But while the damage to leaves becomes increasingly unsightly, it will not kill plants. Apart from removing affected leaves as soon as you notice the brown dots or patches, the only option is to use a systemic spray – Bug Clear Ultra – as early in the season as possible. Astrantias will leaf up and flower a second time in early autumn if cut back after their first flush. Thus you may help control this pest by severely axing your plants. I might add that it seems to have been a bad year for leaf miners (of which there are many, specific to plants from chrysanthemums to holly and chestnut trees).
Dogs and chemicals
A friend of mine runs kennels and the dogs have access to all the land within the property. Weed control is a big problem and she is reluctant to use anything “toxic”. The main weeds are nettles, groundsel and grasses.
GSO, via email
Despite all the recent hoo-hah, glyphosate (as in Roundup) is still with us so I spoke with vet Pete Wedderburn about this. He confirmed that it is deemed safe to use where pets and children play, once it is dry. (see petethevet.com).
Glyphosate does not prevent subsequent germination of seeds already in the soil – so inevitably weeds reappear in due course. Nettles, being shallow-rooted, are easy to dig out in winter. Now in flower, they will shortly set seed. Being easiest to treat with glyphosate while about 9in (23cm) high, there is just about time this season to strim them, let them regrow then knobble them with the weedkiller in very early autumn. But I hate recommending such a “scorched earth” course of action. Wouldn’t an occasional selective strim be better – and not much more trouble?
A new winter front garden
It has been “all change” for Elizabeth Weaver, who exchanged her high-maintenance front lawn for gravel and decided to go for winter colour by planting leathery-leafed bergenias that colour up in winter and flower in spring, as well as a cornus 'Midwinter Beauty’ for its orange-red winter stems. Having never grown these plants before, she asks for advice on how to keep them looking their best: when should she feed and divide the bergenias and prune the cornus?
The bergenias will more or less manage themselves and should gradually expand in all directions, putting out chunky, leafy shoots and producing upright candles of spring flowers. An annual grooming to remove old dry leaves from the evergreen “undercarriage”, where hibernating snails tend to congregate, will keep things smart. In time, any wayward stems can just be cleanly removed, shoved in trays of sandy compost to root and provide new young plants to further expand the colony or give away. An annual sprinkle of blood, fish and bone would be beneficial, though nitrogen-rich feeds will tend to produce larger leaves but fewer flowers: it depends on what Elizabeth has in mind. The cornus, too, is easy to manage. Young stems become colourful in winter, so spring pruning, cutting back a lot of the previous year’s growth to encourage the production of new shoots during the coming summer, is best. However, in its first spring, Elizabeth should prune the shrub sparingly, doing so simply to create a good shape and framework for the future.
In the picture Elizabeth sent me, the area looked really promising, although it had me wondering, since this is intended to be even more “low maintenance” than the grassy garden it replaces, why she doesn’t run the gravel right into the beds that now contain her new plants to give the area a more unified look. Before doing so, she could add hellebore or two (left) and snowdrops perhaps.
Send your questions
Write Helen Yemm, Gardening, The Daily Telegraph, 111 Buckingham Palace Rd, London SW1W 0DT
Email [email protected]
For more tips and advice from Helen Yemm, visit telegraph.co.uk/helenyemm
Helen Yemm can answer questions only through this column