Our Top Annual Flower Planting Tips for Thriving Blooms
Spring is the perfect time to plant annuals like zinnias, cosmos, and celosia. Join flower farmer Briana Yablonski to learn some planting and care tips that will lead to healthy plants and vibrant blooms.
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Spring is here, and that means it’s the perfect time to get many annual flowers into the ground. Whether you dream of growing a row of towering sunflowers or a patch of cutting flowers, spring is the perfect time to plant.
That said, it’s easy to let the excitement of spring get the best of you. So, before you start sticking your annuals in the ground, take time to learn a few annual planting tips. Selecting the right location, planting at the proper time, and tending to your plants’ needs when they’re young are all crucial parts of keeping your garden happy.
No matter what type of annual flower you’re growing, remember these annual planting tips.
Pay Attention to Your Last Frost
Many annual flowers are frost-sensitive, so planting them too early in the season will lead to their demise. It’s easy to let the first stretch of sunny, warm days inspire you to grab your seed packets and head into the garden. However, frost will kill these tender seedlings and make you start all over.
You can rely on weather forecasts and past data to determine when to plant your annuals. I like to start by looking at the historic last spring frost date in my area. While it’s sometimes safe to plant before this date, it serves as a good indicator of when you can seed or transplant.
For example, if your last average frost date is April 10, you shouldn’t stick your starts in the ground if it’s 70°F (21°C) in mid-March… even if there aren’t any below-freezing nights in the forecast. Once you hit this average frost date, you can begin looking at the forecast.
If the next week looks like it will be above freezing, it’s probably safe to set out tender annuals like gomphrena, amaranth, and sunflowers. You can transplant the crops into your garden or direct sow seeds.
While many annual flowers are sensitive to the cold, some can tolerate a light frost. You can plant sweet peas, larkspur, stock, and bachelor buttons outdoors a few weeks before your last frost.
Know Sun Requirements
Many plants like full sun, but most annual flowers require it. Annuals sprout, grow, and set seed all in the same year, and they require a lot of energy to do so. If your seed packet says to plant the crop in full sun, make sure you place it in an area that receives at least eight hours of daily direct sunlight.
If you plant an annual flower that requires full sun in a shady area, you can expect less healthy plants and fewer blooms. They may survive, but they won’t thrive like they would if you planted them in an area with lots of light.
Sometimes, you have to choose between morning and afternoon shade. If that’s the case, opt for afternoon shade. The morning light will dry dew and prevent disease, and your blooms will appreciate the break from the heat that afternoon shade provides.
Plant at the Right Spacing
Proper plant spacing is one of the most important tips when you’re trying to grow healthy annuals. You may be tempted to pack plants together in a small garden, especially when the seedlings are small. However, crowded crops can lead to decreased airflow, competition for water and nutrients, and increased diseases.
Most seed packets list the proper spacing for each variety, so you can check your packet for this information. If you lost the packet or purchased seedlings from a nursery, look online for the correct species information.
If you’re planting multiple varieties next to each other, err on the side of wider spacing. For example, ‘Mammoth’ sunflowers require 24” spacing while ‘King Size Silvery Rose’ strawflower requires 12”. If you’re planting the two next to each other, space them 24” apart.
Keep New Transplants Well Watered
If you’re transplanting seedlings into the garden, it’s important to keep the soil around them moist in the few weeks after planting. These baby seedlings haven’t yet developed robust root systems, so they can only access moisture close by.
Even if it says that flowers are drought-tolerant, this doesn’t apply to them when they’re in the seedling stage. I recommend checking the soil moisture level every day in the first two weeks following planting.
Overhead watering is best when they’re small, since this will ensure they receive enough moisture to grow their roots. You can use a watering can, hose, or sprinkler. If you’re using a drip irrigation system, make sure the emitters are providing water close to the base of the stems.
Pinch As Necessary
While you may hope to see flowers as soon as possible, planning for the long haul will result in healthier plants and more flowers. Pinching is one step you can take to make this happen.
Pinching flowers means removing the terminal bud near the top of the stem. Removing this bud will encourage the plant to grow longer side shoots, meaning bushier plants and more blooms. You can pinch them anytime after they have two sets of true leaves, but aim to complete this task while the seedlings are still small.
When you pinch, make sure only to remove the top bud and keep the leaves on either side. A new shoot will emerge on either side of the pinched stem and continue to grow.
Here are some annual flowers that benefit from pinching:
- Zinnias
- Marigolds
- Cosmos
- Plume celosia
- Amaranth
- Calendula
Watch Out for Pests
Since newly emerged seedlings are small, pests can quickly devour them. While it often takes a while for bugs to find the leaves, you should keep an eye on the seedlings when they’re young.
Slugs, snails, armyworms, and pillbugs are some of the main critters to watch out for. If you see these pests, remove them by hand. You can also tightly cover them with row cover to protect from pests, but be aware that some bugs can tunnel under the soil and still reach your crops.
You should also watch for damage. If you notice chewed leaves but don’t see any pests, look around the plants for any bad bugs. Dig an inch into the soil and check the surrounding weeds and debris.
Remove Weed Competition
Weeding is a seemingly obvious annual planting tip, but many gardeners forget its true importance. The warm weather and long days that encourage annual flowers to grow also cause weed seeds to germinate. If left unchecked, these weeds can grow tall and quickly outcompete your flowers.
Removing weeds is easier when they’re small. You can use a hoe to quickly scrape the soil surface and remove them when they’re in the white thread stage. Keep an eye out for perennial weeds like Bermudagrass and thistle, and make sure to remove all of the roots and rhizomes.
You can also help prevent weeds by mulching your annual flowers when they’re still young. Adding organic materials like straw and wood chips will prevent weed seeds from germinating—just make sure you don’t cover the tiny seedlings.
