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Chrysanthemums
Chrysanthemums are familiar as gift-wrapped pot plants or the florists'
standby. But there are also many easy going outdoor chrysanthemums to
cheer up your garden as winter approaches.
The early flowerers usually start blooming in February - a time when many other plants are past their best - and continue until severe frosts cut them back. Heights range from about 25 150cm and there is a wide variety of flower colours and shapes. They make a welcome splash inside too lasting two or three weeks after cutting.
Where to Buy
In garden centres you are most likely to come across potted chrysanthemums.
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"Bronze Starlet"
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However, you may also find some of the other types here.
For the widest selection you're best to go to a specialist grower. However, we've managed to find only one specialist, mail-order nursery - Coulter's Chrysanthemum Nursery in Christchurch. Their catalogue comes out around June/July, after which time you can put in an order. Plants are sent out bare-rooted in late September, October, November.
You may also be able to buy plants from your local chrysanthemum society. If you want to see before you buy, check when they're holding their chrysanthemum show; Aucklanders could visit the late March/April display in the Auckland Domain Winter Gardens.
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"Irene Arnold"
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Bloom Time
Most of these types are available as early- or late-flowering varieties. Early-flowering chrysanthemums bloom from February onwards. Interestingly, they will only produce flower buds once there have been a certain number of days around 1 15-16°C. From April, the late-flowering types will bloom, but only when they've been growing for a certain number of days with less than 12 hours' daylight. If you live in an area that gets early frosts, you're best to go for the early-flowering ones.
Growing Guide
- Open mail-order plants as soon as you receive them and plant into 7.5-10cm pots with a general potting mix. Plants from garden centres and chrysanthemum societies should already be in pots.
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Grow on until the plant is well rooted and then plant out into the garden in late October/early November. Prepare the soil by digging in plenty of organic matter and add a general or slow release ferriliser. Or use an organic fertiliser like blood and bone, but as it's low on potassium you'll need to add potash as well.
- Plant them in a sunny spot with good drainage, and water in thoroughly. Ideally they should be sheltered from winds while young, but it's a bit of a compromise because air circulation helps deter fungal diseases and mites.
- About three or four weeks after planting, the plants need to be "stopped" (see diagram). This involves pinching out the growing tips to encourage lateral shoots or side branches which will eventually bear flowers.
- Stop them again once the new growth gets to about 15-20cm, and then as needed to shape the plant.
- Cut them down to the ground after flowering.
- Take cuttings from the new growth (see Cuttings) or lift and divide the plants. The advantage of replacing plants by cuttings each year is that you reduce the chance of pests and diseases carrying over.
Stopping - Remove the tip of the main stem to encourage the formation of more flowering stems. |
For a Good Show
Feeding
Apply compost and fertilisers before planting. You can also give them a boost with a liquid fertiliser in January/February. Reapply a general or slow release fertiliser, or blood and bone with potash the following October/November.
Watering
Chrysanthemums resent wet feet, so keep them moist but not waterlogged. This may mean watering daily for those in terracotta pots, and maybe once a week for those in the garden unless there's been a good rainfall.
Pests and diseases
As always, good garden hygiene, the right growing conditions and strong healthy plants will go a long way to resisting pests and diseases. If you have a plant that succumbs to everything in its first year, discard it and try something else.
Rust is the most likely disease. Brown rust causes yellowish spots on the upper leaf surface and rusty brown spore pustules beneath - often appearing as a ring. It tends to spread when conditions are warm and wet. Try to keep the leaves dry and not too shaded and keep plants well spaced and well aerated. Make sure all dead and dying plant material is removed to prevent the disease carrying over from one year to the next. It's best to destroy seriously affected plants. Otherwise remove and destroy affected parts, and if you want to spray, try a fungicide Spray - or the combination insecticide/fungicides. Copper sprays can be used to help prevent it occurring.
Although not very common, white rust is particularly nasty; and plants with any symptoms should be destroyed. It shows up as circular white or yellow waxy spots, later turning brown, on the underside of the leaf. A slight depression develops on the upper leaf surface, which is a lighter green than the surrounding leaf.
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"Margaret"
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Aphids are most likely to be a problem early in the season. Try dousing plants with soapy water or use an insecticide. Check the label claim to make sure it controls aphids.
Flowers and leaves may be chewed by caterpillars. Try picking them off by hand - but you might need to hunt for them in the blooms. If you want to spray, most insecticides will control them - check the label claim.
Cuttings
After plants have been cut down to ground level, take cuttings about 6-7.5cm long from the new growth in September/October. Trim to about 6-7.5cm cutting just beneath a node or leaf joint and making sure there is at least one pair of leaves below the growing tip. Treat with rooting hormone - - we recommend and insert into a 50:50 combination of potting mix and river sand or potting mix and perlite. Water your cuttings in with a fine rose, but from then on restrict watering to a minimum to avoid rot. Cover the pot or tray with plastic and place in a warm spot out of direct light. Roots should form in about three weeks. Pot them up into small pots (yoghurt containers with holes in the base work well) and move them gradually into full sun.
Pot Plants
The "pot mums" are best treated as a house plant. They can be bought in flower all year round because they've been grown in an environment where the temperature and light are carefully controlled. They may also have been treated with a growth retardant.
They don't require any special treatment - just look after them as you would any pot plant.
Once they've finished flowering you can plant them in the garden; you're likely to have the best success if you do this in spring. You may find five plants in the pot. Divide these, keeping any that have a live side shoot coming away from under the soil surface, and discard the others. Cut back each plant to 5-8cm and plant and water well. If they do come away, their height in the following year will probably revert to normal, which may be up to 9Ocm.
For More Information
- Join a chrysanthemum society.
- Coulter's Chrysanthemum Nursery, 183 Weston Rd, Christchurch 5, Phone (03) 355 4656.
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