The best time to plant any plant is during the dormant season – in North America, this is usually late fall through early spring. While it's okay to plant during the rest of the year, it will require more maintenance from you in the form of watering, fertilizers, etc.
The best month to plant flowers in spring is really down to the USDA hardiness zone you live in and the likely last frost date. This is likely to be from around March, but if you live in a northern zone, be sure to plant frost-tolerant perennials until you are happy that the risk to more tender flowers has passed.
The hardiest of flowers can be planted as soon as the soil in your garden can be worked, even if it's several weeks before the last frost of the season. For half-hardy flowers, hold off until a couple weeks before the final frost, and for tender flowers, plant when there's no chance of frost for the rest of the season.
Starting too soon can result in a weak, lanky plant, while starting too late can give you one that is just not ready for the outside world—both will struggle to survive!
Tender annuals — Tender annuals thrive in warm soil and warm air temperatures. They should only be planted once temperatures reach and stay above 55°F. They can be severely damaged or die if they are exposed to frost or temperatures below 32°F.
In fact, many plants — such as spring bulbs and perennials — need to be planted in the late summer or early fall months, depending on your zone, in order to generate enough energy to bloom in the spring. Not to mention, it's never too late to add some colorful annuals to your outdoor space!
Mid- to late-August is often an excellent time to plant fall flowers, as long as the weather isn't still so hot that the plants will suffer heat stress. But don't wait too late to plant, or you'll have a very short window to enjoy your flowers. Check the growing requirements for each plant.
Most flowers should be planted after your region's last frost date. Planting flowers in spring is the most popular time, but perennials do fine if planted in early fall in the North and late fall in the South.
The latest time to plant for most vegetables would be the second week in June with a short harvest time. If planting crops that mature within 50 days, you could plant those as late as the last week in June, but keep in mind the weather will be turning cooler, especially at night. Cool crops are best for late plantings.
Mid-August to mid-October is an ideal time of year to plant new trees, though, that time frame can be stretched into November and December. To be 100% sure, measure soil temperature early in the morning for a few, consecutive days. If your soil is consistently 50° F or higher, you're good to plant.
Gardening in the fall provides a longer period with more 'good' days, as compared to the often tumultuous spring season. Plus, if you plant in fall you'll end up ahead of the game and won't have to rush to get everything done after winter. In fact, a good strategy is to plant perennials when you plant your fall bulbs.
You actually can plant many different edibles and ornamentals in July to squeeze out a second harvest or brighten up faded flower beds, containers and planter boxes.
Flowers that come back up from their roots every year in the springtime are called “perennial” flowers. Some of the best perennial flowers to grow in a garden are peonies, daylilies, coneflowers, and hollyhocks.
Others need to be brought indoors when temperatures reach the mid-40s. Be sure you know this before you plant. Unless your plants are winter-proof, it's best to move them indoors or wrap them up when temperatures are near or below freezing for more than five hours.
Tap Down. Wildflower seeds don't need to be planted in holes; however, they should be tapped down to encourage growth. After you've scattered them over the soil, use the back of a shovel, your hand, or your foot to gently press them into the ground.
Some fast growing fall crops like lettuce and radishes can be planted into late September, but many desirable fall crops like broccoli and carrots need several months of prime-growing conditions to mature before frost and low light levels set in.
Planting a Late-Season Garden
But does that mean you've missed your gardening window for the year? Probably not! There are many crops you can plant well into summer (as late as mid-late August) and still harvest a sizable amount of food.
It's never too late. It just matters what you put into that garden. It's too late to grow tomatoes in your Chicago garden in September because you'll be getting cold weather soon, but you could still grow carrots, radishes, and lettuce plants.
You should always leave a foot of open space around the foundation to prevent moisture build up that can lead to mold and damaging dampness (and to avoid giving insects like carpenter ants and termites direct access to your home). Distance is good for the health of the house—and the plants.
Plants and Planting
Pansy roots will not function when soil temperatures are below 45°F. When soil warms to about 65°F (about two to three weeks before frost-free date), cool tolerant plants can be planted, such as nemesia, diascia, snapdragons, alyssum, osteospermum, mimulus, lobelia and petunias.
September is a great time to plant those fall flowers. There are many varieties that can be planted this fall to start blooming early spring.
Late summer or early fall is an excellent time to plant mums, one of the symbolic flowers of the season. Practically any time in September that strikes your fancy is a good bet, so long as it's at least six weeks before the year's first frost.
It's not too late to plant in your garden! In much of the country, summer still is full steam ahead in August. In other regions, the hint of cooler evenings mean the growing season is beginning to slow down. But regardless of where you live, there's plenty of time left in the season left for growing things!