Tips for Planting Annual Plants

Purple cosmos flowers against a blue sky

Planting annuals in spring is like preparing the grounds for a carnival. Once your annuals are in the soil, expect a gorgeous summer show, complete with vibrant flowers that rival the purples, greens, and yellows of a jester hat. With these tips for planting annual plants, your garden will start blooming before you can say, “Alakazam!”

Knowing how and when to plant annuals is crucial for their success. We’ll walk you through how to prepare a healthy garden bed and plant your seeds or seedlings for blossoms all season long.

What is an annual plant?

Annuals are flowering plants that complete their whole life cycle in one year, growing from seed in spring, blooming in summer, and dispersing seeds before dying in fall. Unlike slow-growing perennials (plants that grow for multiple years), annuals put the “petal” to the metal to give your landscape immediate color from late spring until fall. 

There are two methods of growing annuals: Directly sowing seeds into your garden or planting young plants that you started indoors or purchased from a garden center. First, we’ll walk through the simpler but less-effective process of directly sowing seeds. Then, we’ll take you through the slightly more complex steps of planting seedlings.

Before planting annuals

Annuals can be picky when it comes to soil quality and garden conditions, so start planning and improving your garden in the fall before spring planting.

Fall preparation tips

Order a soil test from your local cooperative extension to determine what soil amendments your garden needs to support healthy plants. Ordering the test in fall gives you time to get the results and amend your soil either in late fall or early spring before planting. 

Spread a 2- to 4-inch layer of organic matter (like compost) over the soil to improve nutrient levels and drainage. Use a spade to work the organic matter into the soil to a depth of about 1 foot. Spreading compost in fall gives compost time to work its soil magic so plant roots get a rich, nutritious treat in spring.

Spring preparation tips

If you are planting seedlings, arrange plants (still in their pots) in groups of threes around your garden. Grouping in threes gives your plants an irregular clustered shape, which looks more natural than plants set up in a line, and ensures a denser, fuller look than individual plants. 

Consider each plant’s sunlight requirements (like full sun, partial shade, or dappled shade) when deciding where plants should grow. Also, make a note of the mature size of each plant to provide adequate spacing. 

Plant your annuals on a cloudy day or in the evening as the sun is setting to protect seeds and tender new plants from sun stress. If you only have one day to plant and it happens to be sunny, shade the area with an upright piece of cardboard or plant flat. 

If you are growing tender annuals, wait until the threat of frost has passed before planting them outdoors in spring. 

Moisten the garden bed with a mist of water prior to planting.

The direct seeding method

Sowing annuals from seed is the simplest process, but it also has the lowest success rate. If it’s too late to start annuals indoors and you don’t want to spend the extra dough on store-bought plants, direct seeding is the way to go.

1. Spread organic or slow-release fertilizer over the area where you plan to plant your annuals. Use 1 pound of fertilizer per 100 square feet.

2. Follow the planting instructions on the back of your seed packet. Sow seeds in rows at the correct depth and spacing, or broadcast seeds by scattering them with a sweeping, even hand motion, or using a hand-crank spreader.

3. Firm the soil with the back of a rake.

4. Gently soak the seeds with a fine spray of water. Keep the soil moist for the first seven to 10 days to ensure successful germination. 

The transplanting method

Sure, digging holes to transplant seedlings takes more time than broadcasting seeds everywhere — but transplants give you immediate greenery without the wait, and they’re more likely to survive the first few weeks for healthy growth and loads of blossoms through the season. Just be sure to harden off indoor-grown seedlings at least two weeks before you plant them so they’re acclimated to the outdoors.

1. Water the plants in their containers thoroughly. Let the water drain for 5 to 10 minutes before removing the plants from their containers. 

2. Gently remove plants from their containers. Do NOT grab the stem and attempt to pull the plant out of its pot, as this can cause stem breakage. Instead …

  • For individually potted plants, place the palm of your hand over the container, with the stem of the plant between your fingers. Carefully flip over the pot and with the other hand tap the bottom of the pot to loosen the plant. Lift the pot off the plant so the plant is in your hand.
  • For plants in flexible trays with individual cells, flip the tray over and gently tap or push on the cell so that the plant pops out of the plastic and into your hand.
  • For plants in peat pots, remove the rim of the pot that extends above the soil surface (otherwise, the rim may cause the roots to dry out). Remove the bottom of the peat pot to encourage strong rooting and good drainage.

3. Untangle roots that have become knotted, compacted, or have grown in a circle at the bottom of the container. Gently break up the root ball with your fingers or a knife. Loosening and teasing out roots won’t hurt the plant and will encourage roots to grow into new soil. 

4. Dig a hole with your trowel at the same level or slightly deeper than the soil in the pot or tray. In general, holes should be spaced at a distance of one-half of the plant’s mature height.

5. Plant your annual. Place your plant in the hole and refill the space with garden soil. Firm the soil with the back of your trowel or your fingers, creating a small moat around the plant’s stem to ensure water filters down to the roots. 

Pro Tip: If you’re planting an army of annuals, try the pro-approved “stab-and-plant” technique. Hold the trowel with the concave (inward-curving) side facing you. Stab the soil with the trowel and pull it toward you to create a hole. Then, drop the plant into the hole and firm the space around it with soil.

6. Water thoroughly around the plant to eliminate air pockets and acclimate your plant to its new environment.

7. Spread slow-release fertilizer. A slow-release granular fertilizer like Osmocote or organic fertilizer like fish and seaweed emulsion will start your annuals strong. 

8. Add mulch. To protect plant roots, prevent weeds, and retain soil moisture, spread a layer of organic mulch like decomposing leaves or grass clippings around your annuals. 

When to plant annuals

The time of year you plant your annuals depends on their hardiness status. Annuals fall into three major hardiness categories: 

  1. Tender
  2. Hardy
  3. Half-hardy

Most annuals should be planted in spring, while hardy annuals may be planted in fall for winter appeal. We’ll give you an overview of planting schedules, but the right planting time for each annual varies based on where you live.

Tender annuals

Tender annuals (aka summer annuals) love the heat and can’t stand the cold. They germinate in late spring, bloom in summer, and die when the first frost arrives. These warm-season, heat-resistant plants are fantastic for hot southern climates and have a very low tolerance for cooler fall temperatures.

Plant tender annuals in spring, two to three weeks after the final frost date. Wait for the soil and air to warm up before planting these temperature-sensitive species, as planting too early can cause plants to stop growing and rot.

For an early start, sow seeds indoors four to six weeks before the final spring frost date. Remember to harden off your plants before transplanting them into your garden. 

Tender annuals include:

  • American marigold
  • Annual geranium
  • Begonia*
  • Coleus*
  • Impatiens*
  • Mexican sunflower
  • Zinnia

* A tender perennial in USDA zones 10 and 11, but grows outside of these zones as an annual.

Hardy annuals

Also known as winter annuals, hardy annuals are the most cold-tolerant annuals, giving your lawn a pop of color in winter, spring, and early summer. In warmer climates, they decline and die during the peak heat of summer. 

Plant hardy annuals in fall, six weeks before your area’s first fall frost date, or early spring, four weeks before your area’s final spring frost date.

For an early spring start, sow seeds indoors eight to 10 weeks before the final spring frost date and plant them in your garden about a month later, after they have been hardened off.

Hardy annuals include: 

  • Annual verbena
  • Broccoli 
  • Dusty miller
  • Larkspur
  • Pansy
  • Pot marigold
  • Sweet alyssum

Half-hardy annuals

Half-hardy annuals are a happy medium between tender and hardy annuals. They’re more cold-tolerant than tender annuals and more heat-tolerant than hardy annuals. Half-hardy annuals can withstand a light frost but are vulnerable to cold damage and won’t last through winter.

Plant half-hardy annuals two weeks before your area’s final spring frost date. If you’re starting your seeds indoors, sow seeds six to eight weeks before the last spring frost date.

Half-hardy annuals include:

  • Ageratum
  • Annual baby’s breath
  • Annual cosmos
  • Annual dianthus
  • Gazania
  • Petunia
  • Strawflower

Benefits of planting annuals

If perennials last for years while annuals only last one season, why bother planting annuals? There are many benefits of annuals: 

✓ Longer blooming season than perennials

Annuals typically bloom from spring until the first frost of fall, while perennials bloom for a shorter window (generally two to four weeks) of the growing season. 

✓ Many color and pattern choices

Annuals are often more vibrantly colored than perennials and come in an incredible assortment of sizes and textures. 

✓ Cover bare patches

When a harsh winter kills off a bunch of once-healthy branches, you can plant annuals to fill in the bare area. That way, your lawn won’t have any awkward gaps in spring and your damaged perennials will have time to recover.

✓ Let you experiment with your landscape aesthetic

Not sure if you want tall red and orange flowers by your mailbox, or if you’d prefer low-growing cool blue flowers? Plant annuals and see how you feel in a few months. You can always change the color scheme next year, whereas with perennials, you’re locked in with a color scheme for at least three years (unless you transplant the perennial, which can be a hassle).

✓ Less expensive than perennials

Annual seeds and seedlings are cheaper than perennials. A package of 12 annual zinnias costs $12 ($1 per plant), whereas a perennial flower, like purple coneflower, costs about $7 per small plant. However, the cost of annuals versus perennials may even out because you have to plant annuals every year. 

✓ Some annuals self-seed for next year

Many annuals like cleome, cosmos, poppies, snapdragons, and sweet alyssum successfully reseed themselves at the end of the season. They produce seed pods and release hundreds to thousands of tiny seeds that start growing the next spring. If you’re content with a wilder, more meadowy look, you can hold off on reseeding and enjoy fresh spring growth without the work.

FAQ about planting annuals

1. What does “hardening off” mean? 

“Hardening off” is the two-week process of acclimating your indoor-grown plants to outdoor conditions so they aren’t shocked by wind, sun exposure, temperature fluctuations, and storms.

Start hardening off your annuals by bringing them to a sheltered, shaded location for two to three hours each day. Take them back indoors at night.

Slightly decrease the amount of water you give your seedlings, but do not allow them to wilt. Increase the amount of sunlight they receive each day over the two-week period. During the last few days, you should be able to leave them outside all day and night. Then, transplant them to your garden.

2. What is deadheading?

Deadheading is the process of cutting flowers as they fade to redirect the plant’s energy from producing seed pods to growing fresh blossoms. It’s a healthy gardening practice used for both annuals and perennials. During the blooming season, you’ll need to cut your annuals’ spent flowers daily or every other day.

3. Can I plant annuals after a rainstorm?

No, hold off on planting when the soil is soaking wet. Slightly moist soil is ideal for planting, but wet soil develops lumps and is prone to compaction, which limits root growth and doesn’t allow the necessary air, water, and nutrients to penetrate. 

After a major rainstorm, wait a few days before planting your seeds or seedlings. You’ll know it’s the right time to plant when the soil crumbles in your hand but holds its shape when squeezed. 

4. How often should I water my annuals?

Most annuals need to be watered once a day for healthy, dense growth. Do not wait for annuals to wilt before watering them. If you live in a drought-prone region or simply want to cut your water bill, you can plant drought-tolerant annuals instead. These hardy growers only require one watering per week.

Use a soaker hose or drip irrigation system, rather than sprinklers, to water your annuals. These systems deliver water straight to your annuals’ root system, which minimizes the potential for water to evaporate before reaching the ground.

5. How often should I fertilize my annuals? 

Fertilize your annuals with a fast-release liquid fertilizer once a week. Look for a fertilizer labeled “complete” or “20-20-20,” which indicates that it contains a 1:1:1 ratio of nitrogen, phosphorus, and potassium (the three essential elements for plant health).

Remember to spread a slow-release granular fertilizer or organic fertilizer at the time of planting. Apply a second round of this fertilizer in late June or early July to encourage annuals to keep blooming. 

Announce the spring with annuals

Planting annuals isn’t a magic trick reserved for the professionals. With some garden bed preparation, a trowel, and a free afternoon, you can craft a beautiful annual flower bed that will make the neighbors cry, “Bravo!”

Not all lawn work is as enjoyable as designing a cheerful, color-coordinated flower garden. If mowing and yard cleanup aren’t your idea of a carnival ride, you can call a team of local lawn care pros to perform yard acrobatics for a verdant, healthy green space. 

Main Photo Credit: manseok_Kim | Pexels

Maille Smith

Maille-Rose Smith is a freelance writer and actor based in New York. She graduated from the University of Virginia. She enjoys watching theatre, reading mysteries, and listening to psychology podcasts. She is an orchid enthusiast and always has a basil plant growing in her kitchen.