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Gardening information, hints and tips on how to look after Dahlias in your garden including pest control, feeding, support and general care advice.

Dahlias Hints and Tips

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Nov

Dec

May

Young dahlias can be planted out from late May onwards when danger of frosts has passed. Dahlias should be planted about 0.75m to 1m apart. Place two or three handfuls of peat in the hole before planting to improve moisture retention around the roots until they get established, firm down well and water in well - it will help to leave a shallow depression around the stem to to collect rain or water when irrigating the garden.
It is essential to stake dahlias as the stems can grow up to 1m in height and the, often spectacular, flower heads can be too heavy for the long stems to support on their own. Stout stakes of 1.5m length driven into the ground are preferred with the stems loosely tied to the stakes using soft garden string. If frost is forecast protect the young plants with horticultural fleece.

Buy seeds and plants from Thompson and Morgan.

June

If you live in the north, you should plant your dahlias at the start of the month. After 2-3 weeks growth, pinch out the tip of the leader, thereby promoting the growth of side stems and creating a good, bushy plant with lots of flowers. Continue to tie them loosely to the stakes as they grow. Pick off greenfly as they appear. Dahlias benefit from a mulch of good compost; don't forget to water prior to putting the mulch on.

July

You will need to continue paying close attention to tying in and supporting growing plants. Plants should be two feet tall by the middle of the month and if you are not confident that this will be achieved give them a good feed every two weeks using a liquid fertiliser onto wet soil – water the soil first if it's dry. Dahlias are excellent cut flowers and in order to achieve long stems you will need to disbud the plants by removing the two lower flower buds from the stem and just leave the main bud at the very top of the stem. An alternative is to remove the top bud and let the two lower flowers develop which will give more but smaller flowers. Deadhead the plants regularly as the flowers fade.

August

Continue to spray for pests and keep an eye out for discoulered foliage which will indicate viral diseases especially if combined with poor progress in growth. These plants should be disposed of and destroyed – do not be tempted to take cuttings from them as the disease will be transferred to the new plant. Feed with liquid fertilizer and continue to provide support to tall plants to prevent wind damage.

Buy seeds and plants from Thompson and Morgan.

September

Check plants are staked well. Feed every 2 weeks with a well balanced liquid fertilizer. To save seed, cut off stems with yellow seed pods, tie in a bunch and hang in a cool place to dry. Remove seeds once the pods have dried out and store in folded paper in an envelope. Don't forget to label them.

October

The first frosts will cause the foliage and stems to turn black - this is the signal that it is time to lift the tubers and prepare them for storage over the winter. Cut the stems down to about six inches above the ground and carefully lift the tubers taking care not to damage them. Remove the soil carefully from around the tuber and store them in a frost free place for a week or two to let the stems thoroughly dry out. The tubers should be stored in boxes with the fleshy part of the tubers just covered with damp potting compost - alternatively you can completely cover the tubers in horticultural vermiculite. The tubers should be stored in a frost free shed, greenhouse or a cool spare room in the house. It is a good idea to have the occasional look at your tubers over the winter - if they seem to be significantly shrivelled you can revive them by immersing them over night in a bucket of tepid water which should plump them up again. Dry them thoroughly and return them to their storage spot.

November

Check stored dahlia tubers and plunge overnight in water if they have started to shrivel. Check for signs of rotting and cut out with a sharp knife. Dust the cuts with sulphur and put back into their storage position.

Buy seeds and plants from Thompson and Morgan.

December

Check tubers and if shrivelled plunge overnight in tepid water. Dry them, check and cut off any damaged parts, then replace in peat.

January

Check stored dahlia tubers and cut off any rotten parts, treating with a proprietary compound. Shrivelled tubers should be stood in water overnight, dried off and placed back in the peat (as with December).

February

Keep a close eye on your stored tubers and if any are shrivelling, plunge them into a bucket of tepid water for the night, dry them off and return them to storage - this should plump them up again so that they remain healthy for the start of the new season.

Buy seeds and plants from Thompson and Morgan.

March

Beds, which need to be in a sunny position, should be dug and dressed with bonemeal, ready for planting towards the end of May.
Spray old tubers in storage every day if possible. This will encourage new sheets for rooting. When these are 4 in. long, remove with a sharp knife as close to the base as possible. Remove lower leaves and cut the stem straight across, below a joint. Dip into hormone rooting powder and plant in compost in small pots. Water and keep in a shaded position, continuing to water until rooted.
Sow seed that you have saved and those of bedding varieties and place in plastic bags or in a propagator. Prick seedlings out once large enough to handle.

April

If the weather is mild, healthy dormant tubers can be planted out. Watch for frosts and protect any shoots that have appeared. Divide tubers to increase your stock.
Rooted cuttings can be potted on and hardened off in a cold frame. Cover on cold nights but provide ventilation during the day.