Growing Dahlias – Cultivation of Dahlia Flowers

growing dahlias

Preparing the Ground for Growing Dahlias

Thorough preparation of the ground for growing dahlias is more important than it is for many other plants. They like plenty of moisture at their roots, and it will be noticed that they always grow better in a wet season. When the ground is moist it is easy for the roots to absorb plenty of the food which is so essential to the dahlia.

The ground should be dug over in the autumn, when plenty of farmyard manure, garden compost, peat, spent hops, shoddy, or any other organic material of this kind should be incorporated at the same time. This will provide humus in the soil, which helps to retain soil moisture. This humus is especially important on light or sandy soils which do not hold much moisture; and on heavy ones this organic matter will help to keep the soil open and well-drained. I do not think that double digging is necessary for dahlias; just dig to the depth of the spade.

After the autumn digging, a dressing of fertiliser should be applied, and I would recommend bone-meal, applied at 2 to 3 oz. to the square yard. This dressing must be put on well before planting time, either just before or just after Christmas, otherwise it will not be readily available to the plants when they are planted, as this fertiliser is slow in releasing its plant foods. Then just before the dahlias are planted apply an all-purpose fertiliser, again at 2 to 3 oz. to the square yard. This should give the young plants, a really good start in life and produce excellent flowers.

When to Plant Dahlias

The time for planting dahlias is very important, and this will depend on the part of the country in which one lives. It is essential to bear in mind that the young shoots should on no account be subjected to frosts, otherwise they will be severely damaged or even killed. Dormant tubers can be planted round about the middle of April in the South, late April in the Midlands, and early May in the North. If the tubers have got long, thin shoots on them when they come out of the store, as they very often have, it is better to cut them back so that no shoots are showing above the ground before mid-May in the South, the end of May in the Midlands and early June in the North, when all chance of frost has gone.

Rooted cuttings may be planted out in mid-May in the South, the end of May or early June in the Midlands, and in the North during the first week of June. Tubers which have been started into growth and are bearing sturdy shoots, should also be planted at these times.

How to Plant Dahlias

The first thing to consider is spacing, and this means that we have to have some idea of how tall the particular varieties grow, in order to know exactly what space to allow between them. The bedding ones need a minimum of 18 in. from plant to plant. The taller-growing varieties, such as pompons, cactus and decoratives, need a minimum distance of 2 ft. between plants, as they grow very bushy. If planting in rows it is best to allow 3 ft. between the rows and 3 ft. between the plants in the rows.

If, when growing dahlias, they are not given sufficient space, they will not receive their fair share of light and air, and, consequently, unhealthy plants will result, together with poor flowering.

Insert the stakes before planting dahlias. This is especially important when planting dormant tubers, as, if stakes are inserted after planting, there is the chance that they may be pushed through the tubers. Tall varieties need a good strong stake to prevent them from being broken off during high winds. Use either oak or soft wood 1 in. square stakes, and treat them with a wood preservative before use. If I use bamboo canes to support my plants, I prefer to put one in when I am planting, and when the plants are growing to put three or four more canes around each plant. Allow all the stems to remain inside the canes, and loop the twine around the entire plant, securing it to each cane. By giving three or four ties up the canes, all the stems should be held in securely. Even better support is provided, of course, if stakes are used to encircle the plants.

Now to planting dahlias themselves. Use a hand trowel for pot-grown plants or small tubers, and a spade for very large tubers. Place dormant tubers, and also those which have been started into growth, about 3 to 4 in. deep. rooted cuttings in pots should be planted so that the top of the root ball is only about 1/2 in. below soil level. Make sure that the pots or boxes have been watered thoroughly before setting out the plants.

Tying Dahlia Flowers

If you have planted started tubers or rooted cuttings, it may be necessary to tie in the shoots after planting to prevent them from breaking off during windy weather. A soft green garden twine is best for this purpose, and should be looped round each shoot, once round the stake, and tied at the back of the latter. As the shoots grow, so more ties should be given. This job should be done at regular intervals until the stems reach the tops of the stakes.

Thinning the Growth of Dahlia Flowers

Any large, old tubers which have not been divided up should have some of their shoots reduced before planting  provided rhe tubers have been started into growth previously. There may be eight or ten shoots on any one tuber, each one of which will be fighting for light and air, and if they are overcrowded they will become drawn and thin They can be reduced to three shoots on each plant; and this applies to bedding varieties as well as tall-growing ones. It will be found that these shoots snap off easily at their bases.

If planting dormant tubers, it will be necessary to wait until their shoots have emerged through the soil, when the surplus ones may be cut off at ground level. With those grown from cuttings there will be no surplus shoots to reduce.

When dahlia plants reach about 8 to 9 in. in height it is a good idea to pinch out the tips of the shoots to encourage strong side shoots to grow.

This will give you a bushy plant and a larger number of flowers. There comes a stage, usually about August, when it is necessary to thin some of the surplus young side shoots higher up the plant, otherwise it becomes a mass of foliage which will result in poorer quality flowers.

All side shoots should be snapped or cut out for about to 2 ft. from the tip of each stem. This thinning will encourage longer flower stems for cutting, and larger and better quality blooms. The shoots lower down the plant should be left to grow, as these will provide replacement stems to flower after the earlier flowers have been removed. Gardeners who are growing dahlias for exhibition, or those who are growing dahlias specially for cutting, usually start this thinning process much earlier than I recommend for garden display, and they should do this task at regular intervals. But for general garden displays thinning is not classed as an important job.

Disbudding Dahlia Flowers

If dahlias are being grown for exhibition it is necessary to remove a fairly large proportion of surplus flower buds. This will result in much larger flowers than if they are allowed to grow completely unchecked. For general garden purposes I do not think much disbudding, if any, is necessary, as you want masses of flowers for a really good display.

As I have already mentioned, exhibition varieties must have their buds reduced in number, but possibly with the exception of pompons and ball dahlias, as heavy disbudding of these results in too large flowers. In this case they may not conform with the official classifications of flower size, and therefore would be disqualified at a dahlia show.

It will be seen that flower buds form at the top of each stem or shoot; one bud, called the crown bud, at the apex of a shoot, with several more just below it. As the crown bud develops more rapidly than the lower ones, this is the one to leave. The lower buds should be pinched out between the fingers and thumb, so leaving one bud only to each shoot. Buds must be removed when they are fairly small.

General Hints for Growing Dahlias

After planting dahlias and throughout the growing season, dahlia plants should be watered abundantly. To conserve soil moisture the area of ground in which the plants are growing can be mulched. A 2 to 3 in. layer of straw, peat, farmyard manure or any similar material can be used. If you are growing for exhibition then try, if possible, to mulch with manure.

As soon as the plants are established and are growing away, they can be fed occasionally with an all-purpose fertiliser, sprinkled around each plant, lightly pricked into the soil, and watered well in. If you have mulched the ground then scrape the material away from the plants first. Dahlia flowers will respond better than any other plant to good and thorough cultivation.

growing dahlias

30. September 2010 by Dave Pinkney
Categories: Bulbous Plants, Plants & Trees | Tags: , , | Comments Off on Growing Dahlias – Cultivation of Dahlia Flowers


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