Chrysanthemum: Growing Advice

Few plants provide so much colour in the greenhouse in autumn as late-flowering chrysanthemums. High temperatures are not required but some form of heat is necessary to overcome cold, damp conditions which can spoil the blooms. The plants can be grown in pots through-out their life or be planted outside for the summer, in which case they are lifted carefully in the early autumn and re-planted in the greenhouse border. I prefer the former method. Varieties

A bewildering number of varieties come into flower from October until the end of the year and new ones are constantly appearing. They are classified according to flower formation and time of flowering. The incurved types have almost globular blooms with tightly packed petals while the reflexed varieties have outward pointing petals. Some reflexed types have reflexing outer petals and inclining inner petals. There are also single, pompon and anemone-centred types.

Heat Treatment

Part of the reason why new varieties are constantly being produced is that stock gradually loses vigour. Virus diseases, for which there is no cure. Can cause this weakening. However, heat-treated plants are obtainable from specialist nurserymen and these will overcome the virus problem.

Stools

After flowering, the stems of the best plants of each variety should be cut back and, after some of the old soil has been shaken off, the stools packed close together in boxes of potting compost. Kept in a light place in a cool greenhouse new shoots soon develop around the base of the old stems. Cuttings can be made from these in January and February.

Cuttings

Use only sturdy, short-jointed shoots, about 3 in. long. The lower leaves are removed and each cutting trimmed below a joint at the base with a sharp knife. Rooting powder is helpful.

A suitable compost consists of 1 part loam, 2 parts moist peat and 3 parts coarse sand. Insert the cuttings round the edge of 3-in. pots filled with this mixture and place them in a propagating frame, or put them directly into a bed of sandy soil in a propagating frame. Water them thoroughly and label all batches of cuttings with their variety. They will root in a temperature of 7°C. (45°F.). Shade with newspaper if there are bright spells of sunshine, and wipe the condensation from the glass of the frame each day. Little water will be needed, but the compost must not be allowed to dry out.

The First Potting

Use 3-in. pots and John Innes No. 1 Potting Compost for the first potting. Afterwards, give the plants a good watering and stand them on the staging, well spaced out and in full light. Encourage sturdy growth by maintaining a temperature of 7°C. (45°F.) and opening the roof ventilators each day unless there is severe weather or fog.

In March the plants may be moved to a cold frame, provided protective material. Such as sacking or straw, is available to cover the frame on cold nights – if the frame is heated so much the better. Water carefully. After potting little water will be needed until new roots develop. When cold, keep the soil on the dry side.

Stopping

The term stopping means re-moving the tip of the shoot to induce sideshoots to form. It is not always necessary as some varieties ‘break’ or produce side stems naturally. These will produce flower buds at their tips in due course called first crown buds. Some varieties, mainly late-flowering ones, are given a second stopping to induce more side growths to develop. The buds which form on these are called second crown buds.

One cannot generalise about stopping: each variety must be treated individually. Most chrysanthemum specialists give stopping dates in their catalogues which can be followed or varied slightly.

The Second Potting

When the young plants begin to fill the 3-in. pots with roots, pot on into 5- or 6-in. pots using John Innes No. 2 Potting Compost. Give the plants a good soaking first so that they can be knocked out of the pots easily. Firm the new compost well around the root ball and leave about I in. of space between the compost and the rim of the pot for watering. Label the pots with the varietal names immediately, then return the plants to the frame and give little water for the first few days after the initial watering. As the plants become re-established, open the frames fully by day to encourage sturdy growth. The Final

Potting

This is usually carried out in early June, as the roots begin to fill the 6-in. pots. Water the plants well a little while before repotting. Use 8-in. pots and John Innes No. 3 Potting Compost which must be made firm with a rammer. Leave space for later topdressing with fresh compost. Remember to transfer the labels.

Staking

It is convenient to stake the plants at this stage. I place three stout bamboo canes in each pot, looping raffia around them to keep the plants secure. Make further ties as the plants grow.

Standing Out

The plants are stood out-side in rows for the summer on an ash base or on pieces of slate to prevent worms getting into the pots. To secure the plants. Stretch wires between strong posts at a height of about 4 ft. and secure the canes in the pots to them.

Watering and Feeding

Inspect the plants at least once a day in summer; two or three waterings may be needed each day in very hot weather. As the plants fill their pots with roots, topdress with fresh potting compost and feed with dry or liquid fertiliser to keep them growing steadily. Feed only when the compost is moist to avoid scorching the roots. Water dry fertiliser in well.

Pest and Disease Control

Regular spraying with a suitable insecticide or fungicide will prevent most troubles.

Capsid bugs, leaf miners and aphids are common pests – all can be checked with BHC. Mildew, causing a white powdery deposit on the leaves, can be controlled with thiram applied as a spray, or dinocap as a smoke under glass. Another suitable fungicide is sulphur, applied as a dust.

Sideshooting and Disbudding

The young growths forming in the joints of the leaves on the flower stems must be removed as they appear except for varieties grown as sprays. Do this with the fingers or a sharp knife. Also disbud to leave one bud on each stem, pinching out the surplus ones while they are quite small.

Housing

The plants must be taken into the greenhouse in the latter part of September, first removing all dead or shrivelled leaves and spraying with a combined insecticide and fungicide. Allow them plenty of space and keep the ventilators fully open whenever the weather permits. A little heat at night in the autumn will keep the air circulating.

01. March 2012 by Dave Pinkney
Categories: Featured Articles, Greenhouse Gardening, Plants & Trees | Tags: , | Comments Off on Chrysanthemum: Growing Advice

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