The Problem SOLVER
Q
My hippeastrum has flowered twice this year. Will it flower again in the new year? Sue Clarke, by email
A
As your plant flowered twice in one year, it may skip flowering in late winter/early spring because it may have used up much more of the bulb’s reserves. To enable hippeastrum bulbs to reflower, they need a temperature of 9-13C (48–55F) from mid-November for around 10 weeks. In this cool period, keep the compost just moist and stop feeding. Remove old, yellowing foliage, but don’t dry bulbs off or cut back healthy foliage. Once the cool period has ended, repot plants if they’ve outgrown their containers or have been in the same compost for two years. Use an open, well-drained compost, adding one part Perlite to every three of multi-purpose compost. Move plants back into a bright position with temperatures of 18C (64F) to initiate flowers. After flowering, and throughout spring and summer, water and feed once a week with a balanced liquid fertiliser. Plants can be placed outdoors in summer, but take care to protect the foliage from slugs and snails.
Q
Why are my sweet pea seedlings so leggy? Abbey Hughes, Swindon, Wiltshire
A
Autumn-sown sweet peas produce stronger plants and earlier flowers than spring-sown ones. However, excessive leggy growth is a common problem, particularly if sown during a mild autumn or sown too early.
You need to get them in a cold frame now. You’ll probably find that growth slows as the winter progresses and as temperatures in your greenhouse fall, you could move seedlings back once this happens, delaying further development. Autumn sowing often means you can dispense with pinching out the growing tips. I wouldn’t worry too much about them having reached 15-18cm (6-7in) and you should find that adjusting temperature slows further growth anyway. However, if they don’t show signs of slowing down, then pinching out may be necessary.
Q
Are pests damaging the leaves of my choisya now? Andy Humphrey, by email
A
The damage to your shrubs looks like it has been caused by caterpillars or slugs and snails. The symptoms of damage can appear very similar and unless you find the culprits there’s no method of determining which has caused the holes. Many species of caterpillars will feed on a wide range of plants. Much of this feeding takes place after dark, so you need to examine the plants by torchlight on a mild evening. If you find caterpillars there may be relatively few and these can be picked off by hand. By now, it’s possible that any caterpillars that have been causing damage have come to the end of their feeding period and have entered the soil and pupated. However, slugs and snails can be a persistent problem throughout the winter during mild, damp weather.
Q
What’s the suede-like covering on the underside of leaves of my holm oak? John Brill, Didcot, Oxfordshire
A
The gingery-coloured hairs that you’ve noticed on the undersides of your Quercus ilex leaves are caused by the holm oak felt gall mite, Aceria ilicis. This is a microscopic pest that feeds by sucking sap from the undersides of the leaves. At the same time, it secretes chemicals into the foliage which induce the growth of the hairs. This growth is sometimes known as felt gall and is common on this species of tree. The mites live and feed among the hairs on the undersides of the leaves until late summer, when the hairs begin to darken and dry up. At that point the mites move on to the bark, where they overwinter in crevices. Apart from creating the felt galls, these mites have no adverse effect on the tree. This is fortunate as it would be very difficult to spray a mature tree and, in any case, none of the pesticides available to amateur gardeners is likely to give effective control.
Q
What do I do with the flowered stems on my dendrobium orchid? Margaret Hanley, by email
A
Dendrobiums are less commonly grown than phalaenopsis or cymbidium orchids, but are quite easy and, with their upright growth, fit well in smaller spaces indoors. Most species produce flowers on new flowering canes, with the old ones gradually dying off after flowering finishes. You can cut the old cane down to the base as it won’t reflower, and support the new developing canes by tying them to stakes.
Dendrobiums prefer being pot-bound and resent disturbance so it’s best to repot plants only when necessary (typically after three or four years of growth). Your plant is still fairly young so I’d continue growing it in its current pot, just ensuring you feed and water regularly in the growing season. When you do come to repot, it’s best done in spring.
Q
Why is the flesh of my ‘Bramley’s Seedling’ apples speckled? Be y Carpenter, Oakham, Rutland
A
This is a disorder known as bitter pit, caused by a calcium deficiency. Calcium is essential to the formation of plant cells and if it’s in short supply, the cells collapse, giving the distinctive small, brown spots, most often found just under the skin. Vigorous varieties are particularly prone. Acidic, sandy soils are naturally short of calcium. In other soils, dry conditions may limit the uptake of calcium via the roots.
If it’s not usually a problem I’d ignore it, but if it’s a regular occurrence, it can be treated. Watering and mulching under trees will help. Sprays of calcium nitrate can also be applied to the foliage from mid-June to September but it may not be practical to spray very large trees. Calcium nitrate is available mail order from Garden Direct (Tel: 0845 217 0788).
Affected fruit can be peeled and used as normal, but won’t store well.