Top 100 Gardening Questions; another ten frequently asked questions

This is the second post in my series of your top 100 gardening questions. I’ve had lots of positive comments on twitter from fellow gardeners, but I also want to hear your gardening questions so please post them on the blog. These can be questions you want answered, or questions you frequently get asked. I’ll answer them in future posts and we will gradually build up your top 100 gardening questions and my top 100 gardening answers.

Q1. I would really like to know how to get rid of invasive weeds safely. I have what I think is ground elder. (posted by Alison on the blog)

A. Most invasive weeds have extensive, brittle roots that are difficult to remove without leaving fragments in the ground which regrow. Ground elder, Aegopodium podagraria is notoriously stubborn always leaving plenty of pieces of rhizome in the soil. You’ve either got to be totally persistent and keep digging it out meticulously, or you use a systemic weedkiller containing glyphosate. This must be applied when the weed is in full leaf, not when you have already removed the foliage. It will regrow and them you hit it again. It’s virtually impossible to remove ground elder from amongst herbaceous perennials; my advice is to sacrifice them and start again. Glyphosate is not residual in soil, but you should only apply it to the leaves and use it in accordance with manufacturer’s instructions. Wear protective clothing and wash after use. (Note: there are some concerns over the persistence of glyphosate; if in doubt then I’m afraid it’s down to digging)

Q2. Have you got any hints on growing auriculas? (posted by Elspeth on the blog)

A. Auriculas are such arresting flowers, but are not the easiest things to grow. They like cool conditions, but not wet. They like light, but hate baking sun. In reality they are best grown in pots for good drainage with alpine grit on the compost surface to prevent rain from splashing soil back onto the leaves. Traditionally they are grown on slatted wooden benches with an open shade cover over them; these structures are called auricula theatres. In my experience they will grow happily in terracotta pots close to the house wall where they are overhung by the eaves. A wooden table on any aspect where the pots get morning or evening sun and shade for the rest of the day is ideal. Use loam-based compost and add extra grit. The single-flowered varieties are the easiest.

Q3. Last winter I grew an amaryllis bulb and it produced three magnificent flower stems. The leaves appeared and grew to gigantic proportions. I put the plant on the patio for the summer and brought it indoors in early autumn. Will it flower again this year? Should I feed it?

A. Whether the leaves have died down or not withhold water completely. Keep the bulb on a windowsill or in a frost-free greenhouse or conservatory in plenty of daylight. Do not be tempted to water until a new flower stem emerges from the bulb; then water normally throughout the flowering or growing season. The bulbs can be fed as soon as the leaves emerge and throughout the summer. A high potash fertiliser such as tomato feed will encourage the formation of flowerbuds. If by any chance your bulb does not flower this year do not despair; just water and feed as suggested from the time the leaves appear.

Q4. I have several Carex oshimensis ‘Evergold in the garden. They have been in for several years and now have ugly brown streaks on many of the leaves, a bit like wind or frost burn. Is it possible to cut the plants back to near the base in spring in the hopes that new growth will sprout?

A. Thanks for your enquiry about Carex. The foliage does tend to get tatty, particularly if the plants get dry or are in sunnier positions. You can trim them back in the spring with a pair of scissors and they will then produce clean, fresh leaves. It’s a good idea to feed at the same time with a slow release fertilizer and do keep the plants well watered.

Q5. Three years ago I planted a Parrotia persica for its extraordinary fall colours. The tree has doubled in size (now 1.2m, 4 ft tall) and although it is pleasant in autumn the leaf colours are not particularly vibrant. Is there anything I can do to improve the colours?

A. It's disappointing when a Parrotia does not colour well, although I have to say mine was quite poor last year and is not good this. Parrotia colours better in an open sunny position. The colour is best on poorer soils; hence it is good on chalk. Avoid too much high nitrogen bulky organic manure and give it a feed with a slow release balanced fertilizer with lots of potash which helps to harden the foliage and should produce better colour.

Q6. I have had a good crop of runner and climbing French beans. I have left some of the older pods on the plants to swell and produce seed. Can I dry these and save them for next year?

A: The simple answer is yes. You can leave the pods on the plants until the pods wither and start to split; then lay them out on newspaper indoors in an airy place until completely dry. Open the pods and remove the seeds. Store them in a cool dry place in a paper envelope. If you store in an airtight box as often recommended you must make sure the seed is completely dry.

Whether it is worthwhile is always debatable. If rust or other diseases have been a problem the seed may carry them to next year’s crop. As the beans will have been open pollinated, the offspring will not be identical to their parents, they will be variable. Next year they will probably be fine but, if you save seed in subsequent years, quality will gradually degenerate. Personally, I would go out and buy a new packet every year.

Q7. I would like to plant a purple-leaved Japanese Maple but I garden on alkaline soil. Will I have to grow it in a pot? Does it need shade?

A: Many gardeners are afraid of Japanese maples (varieties of Acer palmatum) imagining them to be delicate and difficult creatures. The Japanese maples are generally easy to grow plants that are tougher than you think. They are quite hardy and do not need protection from frost. The only cold damage they suffer is from late frosts, when the new leaves are soft and they catch the early morning sun. Their worst enemy is cold wind early in the season when the leaves are unfurling, so plant in a sheltered position or shield them with another larger, wind resistant, evergreen shrub. Although they are not keen on shallow soil over chalk they will grow in alkaline soils, and they are happy on chalk if there is reasonable soil depth. The purple leaved varieties such as Acer palmatum ‘Bloodgood’ need plenty of direct sunlight for best foliage colour, so position in full sun or semi-shade. Acers do not like to dry out at the roots, this causes browning and curling of the leaf tips.

Q8. Please can you give me some suggestions of fast growing evergreen shrubs to provide screening and shelter in a very windy area. There is a small wall, but we want to block out the view of some ugly houses and to protect the patio from a westerly wind. I hate leylandii and am not over keen on laurels or the brown look of a beech hedge. Any suggestions would be very welcome.

A. Here are a few possibilities for fast growing screening shrubs:

Griselinia littoralis. This is an attractive upright evergreen with, pea green foliage. It grows quickly to 3 metres or more and is excellent in windy situations; however it is not ideal for alkaline soils.

Elaeagnus x ebbingei. A strong-growing shrub quickly reaching 3 metres or more with arching branches and leathery dark green leaves, silver on the undersides; tiny fragrant flowers appear in autumn. It succeeds on any soil and is very wind tolerant.

Escallonia macrantha. A vigorous shrub with shiny green leaves and red-pink flowers over a long period in summer. It is an excellent choice for coastal gardens and lends itself to pruning.

Pyracantha can be grown as free standing evergreen or against a wall or fence. It has white flowers in spring and orange, yellow or red berries in autumn.

Q9. I have a lovely Magnolia x solangeana in the middle of my lawn that has grown to 2 metres, 6ft high and bloomed wonderfully for the past five years. I now realise it is in the wrong position; it blocks the view down the garden and gets in the way of the mower. I would like to move it to one side and further down the garden, is this possible?

A. This is quite a large plant to move, but it is possible. It would be best to start preparing in spring. Use a sharp spade cut around the tree vertically to the depth of the head of the spade in a circle 45cm or so from the stem. Repeat this in autumn when the leaves have fallen and then create a trench around the tree using this line you cut as the inner wall of the trench. Start undercutting the tree aiming down slightly below the depth of the trench. Gradually work a heavy polythene sheet or polypropylene tarpaulin under the rootball of the tree, taking care to keep the soil and roots intact. Once the tree is on the sheet, use the sheet to drag the tree from the hole. In the meantime dig a hole large enough to accommodate the rootball. If possible drag the plant and slide it into the hole without lifting. Aftercare is vital: regular watering, mulching with compost and firm staking are the secrets of success.

Q10. I want a rose to grow on a shady wall. Will it succeed, and most importantly will it flower?

A. Most roses will grow and flower satisfactorily if they get more than four hours of sun a day. In shadier situations yellow roses are often the best bet. The old climbing rose ‘Golden Showers’ is often recommended for a shady wall. I’ve had great results with the old favourite English rose ‘Graham Thomas’. This is an upright shrub which also makes an excellent climber or pillar rose. Deep golden blooms and a wonderful fragrance too. The English rose ‘The Pilgrim’ is also a good choice as a shrub rose or a short climber. This has flattened rosette shaped blooms of soft yellow. ‘Teasing Georgia’ is a lovely shade of golden yellow as is ‘Golden Celebration’ which makes a wonderfully full shrub rose or again can be grown as a short climber. If you want a different colour try ‘The Generous Gardener’, a lovely soft pink with a wonderful fragrance. This is a versatile rose that can be grown as a shrub in the open ground, in a large pot or as a climber.