Over last year one of my biggest gardening successes was growing dahlias from seed. I’d heard mixed reports on how successful this method was. With the addition of slugs and snails eating the young dahlias I had low expectations of how many if any, plants I would get. But despite low expectations, I ended up with a mass of dahlia plants. So many in fact we had to give them away. Even the window cleaner got some. So while I am no expert with one-year growing knowledge here is what I did.
I grew Bishop’s Children Dahlias bought from Sarah Raven. I had looked into a few types, some varied in germination, some varied in end results whereas these were meant to be easy. They looked to produce a variety of colours that I was happy to have in my garden.
I lack for a greenhouse or a cold frame. I also live up North in the UK so the winter frosts could have potentially caused a problem. Traditionally these are started in a heated greenhouse to give you a headstart to get the most out of them across summer. If you have access to these things that is great. I’m envious but even without they can still be managed. The seeds are little thin seeds. I used one large seed tray filled with peat-free compost. The seeds were pushed in upright so they were poking out a little. The tray was given water and a lid went on. They had to be kept inside, so initially, they went on the windowsill in our North facing spare room. The light is low in there but I have a couple of IKEA grow lights I put on in the evenings to lengthen the daylight. I don’t know if this was necessary but the IKEA lights are LED types, they don’t get hot like the old fashioned ones so I don’t think they will have done any harm.
I didn’t expect many to germinate having heard about mixed success rates. Just about every single one did and they put on growth rapidly. The seedlings initially grow their rounded leaves before they put on their true more jagged leaves.
From the seed tray, they were moved into 10cm pots to grow on. I grew these in Dalefoot clay breaker compost. At this point, it was still mid-April so there was still a chance of frost. As I wasn’t sure what to do I kept some in the spare room where I’d kept the seed tray. Some went outside in the shelter of a plastic box. The majority went in a really useful box. I moved it out during the day and in on a night until we got into May and the nights were looking warmer.
At this stage, it was tempting to put them in the ground. But I resisted and potted them into a mix of larger pots. Most were 3-litre pots. I reuse the plastic pots, as most can’t currently be recycled, from plant purchases so the size varied. I did this to get them nice and strong before going in the ground. As already mentioned dahlias are slug and snail favourites. The best defence for most plants is to ensure they are healthy enough to survive attacks. While they were in plastic pots on the patio they were less likely to be attacked. The young growth needed pinching out every so often. By nipping off the leading growth you encourage bushier growth and more flowers later on. As they put on growth I fed them with a mix of slow-release fertilizer on the soil surface and a weekly fed of liquid tomato feed. I kept as many of the pots as I could in trays as I was watering every few days to stop them getting too dry.
Once they were up to about 30cm and had filled out I spread them around the border and grew a few in pots on the border. With regular deadheading and more tomato feed, they have given me a mass of flowers through to late October and some hanging on in November. The variation in the packet was great: reds, orange, yellow, pink. The foliage of bishop’s children is rich and dark making for a nice contrast with many of the other late summer plants.
Once the frost’s started hitting I emptied out the ones in pots first so I could get on with planting spring bulbs. Then I’ve dug some out from the border for storing over winter. Opinions vary on whether lifting is necessary but I have clay soil and I think mine would rot. Many people had told me by growing from seed without a greenhouse they wouldn’t have enough time to form decent tubers but I can report they look good. Some are the size of a decent jacket potato. Advice suggests putting them I dry old compost or sand and storing them in a frost-free shed or greenhouse. Mine have gone in the loft. I don’t know that this is a good idea but I’m lacking other spaces.
If they do rot it isn’t a big issue though as I’ve got more seed to try next year. I’m also trying a cactus variety that claims to also be good for pollinators. These will hopefully add a few more colours to the mix and add some variety in shape.
I hope you’ve enjoyed my recount. I am indebted to many people who have advised me through the blog, Naomi Slade’s beautiful book and Twitter about how to grow them and would heartily recommend giving them a try.