Swift always succeeds for me in Glasgow. It is one of the tendersweets, both tender and sweet. The following is some of the information taken from my website.
Extra tender and Sweet (tendersweet) or (Augmented supersweet). The sweetest type with softer kernels. Once picked, the sugars do not change to starches as quickly as the older varieties of sweet corn. Also can be quick to mature and should be ready to harvest in September in the North of the UK, and this is the type that I would recommend.
The seed of this type of sweetcorn, are shrunken in appearance and will need moist (not sodden) compost in order to swell and germinate. A soil temperature of more than 15-16C is required for germination and is best obtained in a propagator.
Isolation of this type is required from standard (Su) sweetcorn varieties as well as from baby and pop corn, or the kernels will become tough and starchy and lose the tenderness. Isolation also required from the Supersweets (Sh2) type of sweetcorn or the tenderness will be lost.
Suggested varieties of Extra Tender and Sweet (tendersweet)
Swift F1. Very early, very sweet and tender.
Lark F1. Mid season, very sweet and tender.
Mirai types. Very early, very sweet and tender.
Supersweets (Sh2) Type. A sweet type but more chewy. The sugar content of this type can be 4 or 10 times that of standard(su) sweet corn. Once picked, the sugars do not change to starches as quickly as the older varieties of sweet corn. The most likely type to be found for sale in the supermarkets. They do not have the creamy textures of standard sweet corn.
Isolation of this type is required from standard (Su), sweet corn varieties as well as baby and pop corn, or the kernels will become tough and starchy in both types. All yellow Sh2 types can be grown together, but Sh2 derivatives such as whites and bi-colours will require isolation to prevent colour contamination.
The seed of this type of sweetcorn, are shrunken in appearance and will need moist compost in order to swell and germinate. A soil temperature of more than 15-16C is required for germination and is best obtained in a propagator.
Suggested varieties of Supersweets.
Extra early sweet.