I doubt if these would grow well there, but do suggest that you like, you should start the plants indoors very early. Because like most herbs, they do best in warm and very sunny locations. To get to the seed stage, they need several months of growing and maturing.

Ksrogers,

How early do you think I need to start them? We do get a few months of hot weather. I read that they're in the carrot family. Are they biennials? If so, I'll never get seeds!

Cumin is an annual. I suggest you start seeds off towards the end of your winter, using a plastic cloche (tent) to help maintain a warmer temperature (like a mini hot-house) for germination. Then plant out once the weather warms up. That will give you a head start.

Propagate by seed, sown in spring. Cover seed completely and keep fairly moist. Ideal temperature is 15-18°C. Seedlings usually emerge after 1-2 weeks. Prefers a rich, well-drained sandy loam, pH 4.5-8.3. It needs at least 4 months of mild temperatures for harvest, so plant as soon as the ground is warm enough and frost-free. Does not tolerate long periods of dry heat. Planting close together will help to support the heavy heads when they mature. Prefers full sun and a sheltered position.

Collect seeds as soon as they are ripe, at which time they begin to turn brown.

Because they are in the carrot family, any transplating must be carefuly done. Most rooting type plants like carrots, radishes, etc, need to be carefully transplanted using all the seed starting soil that is not disturbed when moving from pots. A better way may be to grow in large deep pots and move them outside once weather warms up. Because they need to go to seed, which is a very mature plant, that can take quite some time. An easier one would be coriander, as that likes cool weather and lots of shade, and you harvest the leave as cilantro

Some of the gardening catalogs carry deep pots and deep seed starting stuff that may help if you try to start cumin indoors.

I grew coriander this year by direct sowing and was able to harvest quite a bounty of seed. Coriander (a.k.a. cilantro) has about a 90-105 day maturity. Cumin is a smidge longer at 110-115 days. I'd personally try direct sowing cumin but then again I live in Zone 5/6. Have you tried using cold frames and planter's paper to try and help your direct sown early spring plantings? They do help and you can set up less permanent cold frames and covers over your garden beds and remove them when the temperatures warm. I think I would try that in your zone over indoor starts where possible.

FataMorgana

I love cilantro, and have grown it for many years! Oftentimes I just harvest from plants that have self-seeded.
I think I'll start some cumin plants indoors, as well as some direct sowing. The caution with transplanting carrot family plants is usually that they'll go to seed, isn't it? In that case, transplanting may be helpful.

I think the transplating of Cumin seedlings injures the plants as they have a single sizable larger root and very many hiary type roots that damage easily. A cold frame may help some too as mentioned. Something that is removable, but tall enough to allow the plants to mature a bit longer in colder weather. Coriander/cilantro gets quite tall when in seed (actually fruit) stage. Several plantings of Coriader seeds spaced apart a few weeks gives a more continous supply of leaf herb.

How can I get cumin seed for grwin cumin in Bangladesh?

I just started googling Bangladesh seed companies. There might be some possibilities here...

FataMorgana

Here is a link that might be useful: Bangladesh seed companies