Dahlia Mania – planting and cultivation

Dahlias are one of our signature plants in the cutting garden here at Petersham Nurseries, and come in a myriad of forms, flower size and beautiful colours. Flowering from late June until the first frosts, usually late autumn, these prized flowers have become an iconic part of summer at Petersham Nurseries.
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Cultivation Notes

Dahlias are easy to grow and maintain; plant in a sunny spot, keep deadheading, water well and feed them – we recommend tomato food or liquid seaweed.

Earwigs are often a threat to dahlias, eating the flowers and the leaves. We use organic methods of pest control, positioning pots filled with straw upside down, raised on canes, and dotted throughout your dahlias. The earwigs crawl into the straw seeking shade in the heat of the day. Collect them up and release them as far from your dahlias as possible. Slugs also love dahlias, especially when they first shoot, so protect using normal methods, either a torch and bucket late at night or use nematodes during spring and autumn.

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Planting Dahlias

Planting dahlias really couldn’t be easier. Keep tubers in a dry place until you are ready to plant. You can of course plant them straight into the ground from mid-May onwards or better still you can get them off to a head start by planting into pots, to be planted out once the frosts are over.

This is how we grow our dahlias at Petersham Nurseries – getting them off to an early start in pots inside the glass house to plant them outside in the cutting garden mid-May once the tulips have flowered. In doing this you can have them in flower a whole month earlier than if you start them off outside weeks later.

This method will get your tubers off to a good early start and reduce slug and snail attacks – they just love the new fresh shoots. Plus, the tubers will perform much better if they haven’t sat around in cold wet ground waiting for the right conditions to start sprouting.

How to plant a Dahlia

1. You will need a fairly large pot for each tuber, around 3-litre pot is ideal (roughly the circumference of an open hand). Half fill the pot with a non-peat based preferably organic potting compost.

2.Holding onto the stalk of the tuber settle it onto the compost, there’s no need to splay out the sausage like fingers. Still holding the stem, back fill with compost until the sausage like fingers are covered but you are left with a short length of stalk exposed.

3.Water well as this kick starts the tuber to grow – although don’t overwater too much will rot the tuber. Place inside a greenhouse, on a window sill or even store them in a shed as long as it receives some light it will be fine – a warmer position though will result in quicker growth. Just ensure they are kept frost free.

4.Don’t let the tubers dry out and plant out into their final positions in larger container or the garden boarder come mid-May after the last frosts.

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Settle Dahlia onto compost.
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Holding stalk, backfill with compost.
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Leave stalk exposed.
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After a week or two shoots will appear.

Dahlias are totally invaluable for a summer border, simply stunning planted in large containers displays and breathtakingly beautiful close up, when cut and arranged in vases that adorn the tables of our restaurants.


VIEW OUR SELECTION OF DAHLIA BULBS HERE

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