First, you'll need to buy the plants, seeds or bulbs of the flowers you'd like to grow. Remember to pick varieties that do well in your local climate. No need to stick to one group either. Try a few out, and see what works best. Some flowers grow better in different climates. It might take a little trial and error, but you'll soon figure out what flowers are the best to grow.
You'll want to get some plug trays. These are the easiest way to grow hundreds of flowers in a small space. Once the flower seedlings are ready, you pop them out of the tray and put them in the garden or pot.
If you don't have a greenhouse, you can build an indoor growing rack for under $200, which should have enough room to grow 600 plants. Buy a shelving unit (Costco and Home Depot should carry one of these) that has at least four shelves, is 4' across and 18" deep. Next, buy 48" shop lights with full -spectrum bulbs and hang them from the bottom of each shelf (except for the lowest shelf), so that the light is 6" above the shelf below it. You want your plants to get 16 hours of light a day.
Next, you'll want a healthy soil mix. Only use organic materials. Don't use a chemical fertilizer. It might be tempting, but trust me, stick to an organic fertilizer. Organic fertilizers will help your plants grow at a steady rate without a lot of stress. Also, be sure to use compost and cover crops. You can make compost yourself or buy from another composter.
You want to control weed growth too. Put some mulch in your garden. Or you can do what many commercial growers do, and that is to use a polypropylene weed barrier fabric, which has holes cut where the flowers are growing. This does cost more than mulch, but it can be used over and over again for several years.
You'll also want to stop any pest problems that could come your way. There are many different products available, such as pyrethrums, insecticidal soaps and "sticky traps." And don't forget about the damage that wind can do. If your flowers are particularly exposed, such as there isn't a building or trees nearby, consider planting some tall shrubs that can act as a windbreak.
If you get your plants growing healthy, you'll soon start to see results. Just remember this checklist of things your plants must have:
Protection from wind, weeds and pests
Good flower garden design is the result of good planning. Be careful not to place too much emphasis on a colorful spring, also plan ahead.
Plan ahead and enjoy the best results
Make sure to plan spring, summer and autumn bloomers. I know the months after the grey winter we are drawn outside and are prepared to work out butts of, but with some planning your garden will be an explosion of color and a quick succession of blooming flowers the whole gardening season.
So if you want your garden to look good in spring, summer and autumn, do some planning at the start. If you are going for annuals, choose plants that bloom in all seasons where possible.
Choose those with longer blooming seasons over those that only bloom for one or two weeks. Consider all the work you have to put in, plant, water and weed. And the net result is two weeks of bloom. This to me sounds like a waste. If you really adore those short bloomers, then go ahead and put them, but mix in some longer bloomers too.
Mix Annuals and Perennials
If you mix annuals and perennials in the same garden, you can put the perennials into the middle and keep the short annuals for the edges. You could alternate things like mondo grass and pansies for an attractive edging, and then when the pansies are starting to fade off, you still have the mondo grass.