
Nick Gilbert has been growing Dahlias for Gilbert’s Nursery for the past 19 years. The nursery is in Sherfield English, near Romsey, has a 3-acre field displaying a wide variety of dahlias as well as a tearoom. He started with 12 different varieties of Dahlias but now has over 900 varieties and hybridises them. Shipping to Europe stopped after Brexit but he is one of the well-known dahlia producers in the UK.
The dahlia is the national flower of Mexico. The Aztecs originally used them as a food source. They were named after Anders Dahl, who introduced them to the UK in the late 18th century. They were also used as water pipes. Even today there is a variety called Blackjack that one famous UK chef uses for culinary purposes.
All tubers are British grown, grown in peat free compost (Melcourt Sylvagrow).
In October they collect seedheads, usually those from solid round flower varieties. They look for pointed heads to show that the head has gone over, cut off the buds to a set of leaves. After 7-10 days more buds will usually bud and produce flowers. The seedheads can be stored with the petals stripped off exposing the seedhead, they are put in trays to dry, the heads are squeezed to remove moisture, then a papery shuck is formed, then it should be sealed and left until spring when the seeds from the shuck can be sewn in trays, potted into 9cm pots and finally planted out at the end of May/ beginning of June. I seed head can produce up to 100 seeds. They also pollinate by hand with open centred dahlias. The nursery has over two acres of seedlings. If anything unusual grows it is marked up, grown for three years and then taken to RHS Wisley where a decision is made if the dahlia is good enough to name and be placed on the worldwide dahlia register.
October is the month when the Nursery prepares for winter. Nick advises leaving Dahlias in the ground if your soil is free draining, with clay it is best to lift and store them. If you disturb and replant in autumn, you are likely to lose the tubers. Foliage left on the plant helps it to store better. Although the books suggest cutting 8-10 inches above ground level, they have found that a better method is to remove the surface soil, cut the stems off then mound up the existing soil with old compost. This stops too much moisture. If ground is wet, lift the tubers, wash all the soil off, stack in crates until dry, cut the stems level with the tuber. Then store in newspaper in a box.
When planting look out for dahlia gall, a bacterial infection. It is more prevalent if using peat free compost. Anything affected should be burnt, not composted.
Over winter check tubers and cut off any rot, The tuber size is irrelevant. To prevent any more rot, use yellow sulphur. In mid-March if using a greenhouse put tubers in compost and within 7-14 days you should see growth. Leave the first set of leaves there, dissect the leaf nodes (similar to treatment of geraniums) , use rooting powder and plant in modules. Put 6-8 cuttings in 9cm pots, use good quality compost with grit and within 10-12 days new shoots will appear. Growing from cuttings is a more vigorous way of getting more flowers. Put the new shoots in 9cm pots, ready to plant out in mid-May/ early June. Plant 8-10 inches deep and feed with Blood, Fish and Bone.
Dahlias need feeding every 9 weeks throughout the season. Nick uses Blood, Fish and Bone, the last application being in October ready for winter. If using tubers in mid-April plant them 10 inches deep, earth the soil over the top. Best to wait for growth in the pots before planting if you have space.
Slugs: These can be a pest. Nick advises putting pellets on the ground containing pheromone in mid-March before the slugs arrive. Use a light dressing of pellets, Growing Success- Slug Killer Advanced- used by organic farmers. These do not harm wildlife.
Support: All dahlias need support except for dwarf varieties. Use 6” square netting, 2 ½-3 feet in height to start. For a single plant us 1m line, good canes and make a triangle of 3 around the plant, always use soft string so as not to damage the plant.
Diseases: Distancing: Yellow dots on the foliage, identified as dahlia smut. Brown marks on leaves are a result of poor air circulation. Strip off all leaves affected and burn (not in compost). Dahlias that don’t grow sometimes have mosaic virus which is an infection in the tuber so these should be burnt also. Blackfly can be a nuisance, use a strong washing up solution or Nick suggests SB Plant Invigorator which is a plant pesticide and prevents mildew. This helps prevent aphids.
Tips: If you want early flowers use shade netting which helps early buds. When cutting dahlias, do so early morning or last thing at night. Cut the stem and ensure it is hollow to allow water to travel up the stem. If not hollow, cut again. To prevent earwig damage put a cane next to the plant and that will encourage them to grow up the cane away from the plant.
Nick showed us a variety of different shapes and sizes: Large decorative, Giant decorative, Daisy type, Pompons, Ball shape, Collarette. Popular Varieties are:
Bishop of Llandaff - good for pollen
Twinings After Eight - good for pollen
Kelvin Floodlight - size of a basketball
Café au Lait - large decorative 10 inches across, giant decorative 18 inches across
Totally Tangerine - daisy type
Little Snowdrop - pompon size of a thumbnail
Cornell bronze - ball shape, strong stems
David Howard - collarette type, good for bees
War of the roses - red/white, vintage pompon
Plenty of choices and inspiration for us!
Katrien Burrows
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