Although the summer is now well and truly behind us, September is the peak season for garden chrysanthemums. Most gardeners can find room for a few of these plants in the garden or allotment, and if you have some spare glasshouse space after the tomato crop you can extend the season into November or even December in a mild winter or with some added heat if frost threatens.
The starting point for most folk is the admiration for those magnificent blooms on display at a flower show, or growing on some ones allotment, especially if they are showmen and are just about to take the paper bag off a flower that is ready. Everybody wants to know what is under those bags. Then, can the grower be persuaded to part with a cutting knowing that you just might end up being a competitor. However those first few cutting are very special and get maximum attention lavished on them as you try to grow them to the highest standard. There is always a but, and as you do not have the years of experience of the serious competitor, your results are brilliant but not yet quite ready for the show bench. However they will make excellent cut flowers for the home.
Once the bug gets under your skin and you grow for exhibition, this hobby is very demanding of your time, but the end results can be very satisfying.
Other chrysanthemum enthusiasts may be quite happy to grow for garden and allotment display and cut flower for the house.
Types of chrysanthemums and season
If you are an exhibitor you will need to be aware of the official classification to enter your blooms in the right category for showing, but if you just want to grow them for garden display and cut flower you do not need to get bogged down trying to sort out the differences between a reflex, incurve, spray, anemone, fantasy, single or whatever else you find in the chrysanthemum catalogue.
However, whether you buy from the specialist grower such as Woolmans or Harold Walker, or get a few cuttings from a friend, keep the type and name recorded as you will need to know its season and whether it gets disbudded or not.
There are several excellent chrysanthemum growers who can supply collections of one type or another so every year you can try out something new, keeping those you really like, but discarding the rest if they don’t meet your needs.
The first blooms usually come from the early outdoor chrysanthemums in late August and September. These can be incurved, reflex, or sprays.
These are followed by the October flowering varieties of incurves, reflex or singles usually as sprays which will all need some weather protection in a cold greenhouse.
The November and December varieties will also need protection and also some heat if cold weather prevails. The October to December flowering plants can be grown outdoors in pots or baskets planted in soil all summer then brought into the greenhouse in mid autumn.
Chrysanthemums are also grown as pot mums as a house plant flowering all year round. Flowering is controlled by adjusting the light level duration with polythene blackout curtains, and growth is kept dwarf with a chemical growth retardant. The amateur gardener does not have access to the growth retardant, so although many people retain the pot plant to grow the next year, it will revert back to its normal height and may not be suitable as a pot plant. However some height restriction can be achieved by frequently pinching out shoot tips to make it branch, though this has its limits.
At the end of the season plants are cut down to six inches and the stools dug out of the ground shaking off the soil then boxed up in fresh potting compost. These can be overwintered in a cold frame or cold glasshouse as long as it is fairly frost free. They are hardy, but don’t push it.
I had a lot of plants in 2010, so left many in the ground to overwinter. None of them survived and even in the cold glasshouse many died out as the winter was long and cold. Keep the stools on the dry side, but add some water if necessary to keep them alive. Start them into growth in January or February. Take cuttings about two inches long from the stool and dip them in rooting hormone and dibble them into pots boxes or cellular trays in a free draining rooting compost. Place this in a warm light place but not in direct sunshine. They should root and be ready for potting after three weeks or so. Pot up in small pots, then larger pots in a soil based compost. Plant out in late spring.
They can be grown in well manured soil spaced at fifteen inches apart and staked individually with a cane. If you grow a big batch it is quicker to grow them in a two foot wide bed and secure them with a roll of six inch weldmesh or wire fencing. This is held tight between four posts and raised as the plants grow. I plant mine at one plant in each square and do not pinch out the tips to allow one flowering shoot per plant.
If you grow sprays you do not need to disbud, but if you want one large single bloom you need to disbud leaving just the one terminal flower bud to develop. Remove side shoots as well as flower buds.
Keep them fed, watered and weeded throughout the growing season
Pests and diseases (some)
Chrysanthemums can be prone to attack from a wide range of pests and diseases, but the main ones are greenfly, slugs, leafminer and earwigs and the two main diseases are white rust and mildew.
In modern times with very few chemicals left on garden centre shelves, the answer is vigilance and good growing conditions.
On a small scale it is possible to spot and remove most pests before they do any significant damage, and fungicides containing myclobutanil, available for rose problems will help control diseases, but any leaves affected by white rust should immediately be removed.