Telegraph

Thorny problems: jacaranda (Filed: 27/10/2001)

Helen Yemm on leylandii, worms and what to do with a balding lawn

Up a gum tree

I need to hide the 45ft mobile phone mast that dominates our garden. I know that leylandii would do the job, but someone has suggested I transplant a 15ft poplar instead. Do you have any suggestions? Michael Dodd, East Horsley, Surrey

I AM glad you have hesitated before giving the world another leylandii.

Hiding something 45ft tall is hard. In a way, it is easier to distract the eye by planting something really beautiful, even if it fails to obliterate the eyesore completely.

Transplanting the poplar would not be without risk. However, you would end up looking at a fairly ordinary tree that would have no leaves in the winter.

You do not say how much space you have to play with, but since you have rejected the idea of the conifer and are considering the poplar, how about planting a eucalyptus tree instead. Eucalyptus is palely evergreen, extremely vigorous and can be easily manipulated by periodic hard pruning. If you would like to see some of the many varieties growing, you are in the fortunate position of being only a stone's throw from the RHS garden at Wisley, where there are masses on Battleston Hill.

Worm works

How and why are worm casts formed in lawns and why do they appear only in the autumn and winter? Is there a cure? David Jackson, Seaton Sluice, Northumberland

Earthworms spend their lives channelling through topsoil (the layer near the surface that contains humus and all the useful micro-things), feeding by taking in earth at one end and passing it out the other. The earthworms in an acre of ground may shift 18 tons of soil a year.

In dry weather worms work farther down, where the soil is still moist and edible. Come the autumn rains, they shimmy up to the surface, often pulling leaves and other vegetable matter down into the soil, where it will eventually rot to make food. It is at this time that all the worm casts, those little curled up piles of processed soil, appear on our lawns - and in our flower beds, where they are less visible.

When considering a "cure", it is as well to keep in mind the benefits that worms bring to our gardens - aerating the soil, which so easily gets compacted, and fertilising it by pulling down that vegetation. There is no chemical treatment for worms. Carbaryl (the chemical that was in the old-fashioned treatment for head lice) has been taken off the market for safety reasons and any other treatment is so temporary it is hardly worth the bother.

All we can realistically do is sweep the casts off the grass, if it is ever dry enough. But there is no getting away from it: wormy autumn lawns, always damp and still growing enough to need cutting, do look awful. Is this what is meant by global worming?

Bare repair

I have recently raked my mossy lawn and it now has unsightly bare patches. I want to reseed these areas but would like to go about it in the correct way. Can you help? Guy Allan, Old Coulsdon, Surrey

There is still enough warmth in the soil to reseed the bald patches, but you will have to be quick. Grass seed germinates best between March and early November. As you are probably aware, the moss you so carefully removed will inevitably return without treatment.

To reseed, rough up the soil with a lawn rake or lightly fork over the top two or three inches, adding sand where the soil is badly compacted. Mix some grass seed (about a handful per square yard) with a little seed compost, sprinkle it over the patch and pat the area down with the back of a spade. This will hide at least half of the seed from marauding pigeons.

At this time of year, you will not need to water the patches, but you could put small pieces of chicken wire over them to protect them. Depending on the weather, the grass should germinate in about 10 days, but it will not grow robustly until the spring.

Seed success

Hats off to James Taylor from Cheltenham, who has grown a jacaranda tree from seed (presumably Jacaranda mimosifolia, a deciduous tropical tree with pretty leaves and stunning blue flowers). It is now 3ft high in a large pot and has not flowered. He is wondering about its future. It probably won't flower unless it grows to double its present size, and it must be over-wintered indoors.

Blueberry pots

John Haydon emailed with a similar question about his little blueberry (Vaccinium) plants, presently in pots. These natives of North America are just about hardy here and can be planted outside in a sheltered spot as long as they can be provided with an acid, moisture-retentive soil. Otherwise, they should be potted on into larger containers with ericaceous compost and watered with rainwater.

Kindest cuts

Tara Buckley from London wants to know if she can prune her potted Japanese maple, now seven years old and getting a little too big. Yes - but do it sensitively so as not to ruin the shape of the tree. Cut out over-long branches, rather than giving the tree an all-over "haircut". The same advice goes to readers who are worried about ruining their magnolias by pruning them. A magnolia given a "haircut" would also be reluctant to flower.

Write to Thorny Problems at helenyemm1@aol.com or Gardening, The Daily Telegraph, 1 Canada Square, London E14 5DT. Helen can answer queries only through this column.

-- Anonymous, October 29, 2001