Please talk to me about starting cannas and dahlias indoors

[Koulibiak]

I want to grow cannas and dahlias from tubers/rhizomes for my garden this summer.

I live in London - our last frost is usually mid to late March. My garden is quite warm - southwest orientation, black fence, etc. Even non hardy plants (eg Ensete maurelii, pelargoniums, sago palms) survive the winter outside with no or little protection.

i don’t have a greenhouse.

1. can I pot the tubers and keep them in my kitchen (roughly 20C, give or take a few degrees) to start them?
2. if so, what would be the right location: on a windowsill (I have a very deep one, can fit many pots) where it is a bit cooler, or on the floor by a patio door, where they would receive heat from the underfloor heating?
3. when should I start them?
4. any other advice? I’ve already researched the potting medium, pot sizes, feeding and watering etc.

TIA 🙏

I live in London - our last frost is usually mid to late March. My garden is quite warm - southwest orientation, black fence, etc. Even non hardy plants (eg Ensete maurelii, pelargoniums, sago palms) survive the winter outside with no or little protection

Oh my. Where we live you can't guarantee it being snow free in April, never mind frost free!