Canker and crocuses

I enclose a root of mangold which has had some underground gnawing and regretfully I have suffered this with several of my root crops, i.e. parsnips and beetroot.

I enclose a root of mangold which has had some underground gnawing and regretfully I have suffered this with several of my root crops, i.e. parsnips and beetroot. This seems to happen every year and I wondered how can one fore stall this problem as it not only disfigures the crops but are loosing some as well. F Tays Ashby St Mary.

The problem to me looks like Parsnip Canker. This can be a serious disease of parsnips especially in wet soils or during rainy seasons. Although the splitting you are getting on your crops could be caused in part by irregular watering, this could have been worse last season due to the very hot summer.

Canker can manifest itself as spots, blotches and lesions that penetrate the crown, shoulder or sides of the parsnip root. Spores that are produced on foliage fall to the ground where they come in touch with the roots. There are 3 types of canker which can affect parsnips: Black canker Orange-brown canker and Black-brown canker.

The cause of black canker is fungal in origin Infection may be by Intersonilia pastinaceae or Phoma sp. Other pathogens may also be present.


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The cause of orange-brown canker has not been defined and may be physiological in origin. Brown-black canker is also caused by fungal infection Black canker is the most frequently occurring form.

Symptoms of black canker. On foliage small pale green or water soaked flecks which may have a paler halo. Lesions on the shoulders of the root, darkbrown/black or purple black in colour, frequently flecked with orange colouration.

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Lesion size can vary from a few millimetres to several centimetres. Young lesions are coarse or granular in appearance. Sunken lesions can occur on the root surface. The underlying tissue can have a rough scruffy appearance when exposed.

Invasion of the lesions by secondary rot bacteria or fungi can cause rapid decay of the whole root. Intersonilia can remain active after foliage dieback, increasing the risk of canker in late harvested crops. Crops already weakened or damaged by pests are more readily infected than strongly growing crops.

Preventative measures include crop rotation: Ideally do not grow on the same land within 4 years and avoid planting other susceptible crops such as beet, celery or carrots. Cereal breaks are the preferred option.

Control carrot fly attack to avoid secondary infection by the pathogen

Ridging up Ridge up just before foliage meets within rows, making sure there is no damage to roots. Prompt disposal of debris to remove source of infection.

Cleaning of machinery to avoid cross contamination to uninfected land

Good drainage. Regular monitoring of disease levels and appropriate control with fungicides. There are a number of resistance varieties that will be worth trying and limit the length of time you store your root crops.

Q I have always been a keen gardener who started when I was about 10 years old. I now live in Holt and the reason I am writing to you is that I have a lawn in my back garden and both last spring and this I have 2 large groups of purple crocuses, which I have never planted. They looked more like wild crocus, because the stems are longer than normal crocus and the flowers do not open.

Where do you think they have come from and how did they get into my lawn? Crocus don't have seeds in the middle, do they, if so I can only think that the birds have been busy in my garden.

C Durdin Holt

Crocus do set seed and these could well have been dropped on your lawn some years ago and have only just reached a flowering size. The most likely answer is that they were planted by squirrels that have dug them up from another garden and buried them in yours expecting to dig them up as winter food.

Crocuses are very easy to grow, requiring minimal maintenance, and are relatively disease free. They can be used at the front of a border, naturalised in lawns or under and around trees. They also look good when grown in containers.

These large flowering crocuses are the most commonly grown. They can often be seen in bedding schemes and growing naturalised throughout the gardens of England during March and April. All these Dutch hybrids are from C. vernus. They require well-drained soil in full or partial sun.

Spring-flowering bulbs are best planted from late September to November. A bulb planter helps to take out a core of soil, however, a trowel is just as suitable

Plant deeply at about 6cm to 10cm deep (3in to 4in) and the same distance apart add grit and general-purpose compost when planting in poorly-drained soil. Apply a general purpose fertiliser after planting and work it in lightly with a rake or fork

Always let plants die back naturally after planting crocuses unlike daffodils do not need deadheading. Crocuses that are in containers will require feeding with a low-nitrogen, high potash liquid feed (such as tomato feed) every two weeks during the growing season.

To create a natural look on less formal areas of a lawn, it is best to freely scatter the corms over the planting area and then plant them where they fall.

Division is the easiest method of propagation. After several years, clumps can be dug up in the autumn and the bulbs divided and replanted.

Seed propagation can be used for some species, such as C. tommasinianus, will seed freely around the garden. Seed can be collected from the plants. Species of crocus should produce plants that are true from seed. Seed from cultivars might produce some interesting variations. Sow in a well-drained compost when seeds are ripe. Most species will usually flower three years after sowing.

Crocuses aren't disease-prone and are fairly trouble-free. The main pests are squirrels, rabbits and rodents that dig the bulbs up. To prevent this it might be necessary to place chicken wire over the planting area. Plant crocuses deeply to deter squirrels. Some growers quickly dunk the bulbs in paraffin prior to planting as the smell deters the squirrels.

Events

t Garden design event Friday 4th and Saturday 5th 10am to 4pm the event will take place at the Forum in Norwich. Get your garden designed by students from Easton College and buy some unusual plants from a range of specialist growers from across Norfolk. This is a free event run by Easton College and BBC Voices project.

t How to be a gardener part 2 at Easton College Wednesday 2nd May 1-3pm.

The workshop session will look at sowing seeds for the best results and how to grow the plants you raise in the right place and how to plant them out for the best results.

Places on this workshop need to be booked in advance and cost £10. please call 01603 731219 to book and for further information on this and other courses at Easton College.

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