The sowing season starts this month and becomes more frenzied with every passing week. And timing is all. It depends on where you live, the season, and individual seed varieties.

When opening a seed packet, I know it sounds pretty obvious, check the recommended sowing times and stick to them. Simply sowing when you feel like it, can have disappointing results. Many varieties, especially the most recently launched ones, have been developed to mature at fairly precise times.

Seedsmen usually give quite broad sowing parameters, so you’ve some leeway, depending on weather conditions and where you live. As a general rule in Scotland, choose a later recommended date if sowing before the longest day and an earlier one afterwards. This guarantees the strongest possible sun and highest temperature. A sheltered west coast garden will be 2-3 weeks behind the south of England, with higher, northern slopes a good month later.

When planning for succession, see how quickly or slowly varieties take to mature. After planting, some cabbages take as little as 60, with others as much as 120 days. Caulis have a range of 55-90 days and broccoli 55-75 days. With peas and tatties, the labels 1st Early, 2nd Early and Maincrop refer to growing, not planting time.

Ensure a steady succession by sowing and planting these different types of cabbages, potatoes and peas in a oner. Alternatively, with some quick-growing varieties, you can get the same result by sowing the same variety successionally. One of the stars in my kitchen garden last year was broccoli Sibsey. With only 40cm between plants, it matures in 90 days. This gives me 3 sowings between mid March and early June.

One of the techniques plant breeders use to develop new varieties is to manipulate temperature. With cauliflowers, researchers have found that 15C is the ideal heat for summer varieties to mature. When hotter than 22C, curds take longer to form, or simply don’t and become what we call ‘blind’. Despite this, scientists have developed other varieties that don’t conform to these temperatures and can grow well even in India.

One aspect of temperature control is vernalisation. This is a process whereby plants complete their growing programme after a period of chilling.

In some overwintering plants, such as cauliflower, a group of proteins prevents the plant from forming a curd and flowering in its early stages. But during a cold period, these proteins are gradually switched off. So with increased light and higher temperatures in spring, the genes that encourage flowering are released and the plant grows to maturity.

Plant breeders sometimes induce vernalisation. As well as giving us a wider range of plants, we have to apply the vernalisation principle when growing garlic.

Garlic cloves should be planted when there will be a 1-2 month spell with temperatures between 0 and 10C. This chilling ensures we’ll get a good head of garlic, not one giant clove. It also explains why people in the warmer south must plant garlic in autumn, rather than February, as many do here.

There’s also some confusion about what is meant by hardneck and softneck varieties and whether they should be planted in autumn or spring.

You can plant either type in autumn or spring, but hardnecks are more hardy and able to withstand a severe winter. A safer bet for autumn planting. On the other hand, softnecks produce more cloves per head and store better. My preference is to sow softnecks this month.

Buy certified seed of a named variety, avoiding supermarket heads that have been in cold store. They’ve been vernalised, so will grow away as soon as planted, regardless of the weather.

Plant of the week

Mahonia ‘Winter Sun’. Winter sunshine releases the delicious fragrance. Arching racemes of yellow flowers glow from the shade and the architectural leaves make a handsome shrub all year round.