Annuals and Perennials: Two Ways to Fill a Flower Garden
Flower gardening for beginners can feel like a big leap, but breaking it down into two main plant groups makes it easier. Annuals and perennials each have a role, and understanding how they work helps you plan a garden that looks good from spring through fall. If you are just getting started, our Plants and Growing section covers the fundamentals.
Mississippi State University Extension explains that annual plants are versatile, sturdy, and inexpensive. They quickly yield color for one long season. Perennial plants return year after year and can be used in borders, as accents, or as strong focal points. The foliage of many perennials is attractive during nonflowering seasons as well. Knowing this difference helps you decide where to place each type in your garden.
Giving Annual Flowers a Head Start Indoors
Many annual flowers need an indoor start if they are to bloom during the summer, according to the University of Minnesota Extension. In Minnesota, annual flowers are usually started indoors in early spring, but the exact timing depends on your local frost dates. Always check your state’s extension service for guidance tailored to your area.
The University of Minnesota Extension recommends starting seeds in small, individual containers with drainage holes. Use a commercial seed-starting mix, which is sterile and lightweight. Fill the containers, water the mix, and sow seeds according to the packet. A rule of thumb is to plant a seed two times as deep as its width. Some seeds need light to germinate; cover those with a thin layer of fine vermiculite. Others need darkness, so cover them with dark plastic or newspaper until they sprout.
Seedlings grow best under fluorescent or LED lights. The University of Minnesota Extension advises keeping lights no more than 4 inches above the tops of seedlings, with 2 inches being ideal. Provide 12 to 16 hours of light daily; a timer can help. Bottom heat from an electric mat can speed germination and help prevent damping off. Keep the potting mix moist but not waterlogged, and drain excess water from trays.
Once seedlings have several sets of true leaves, the University of Minnesota Extension suggests feeding them with a weak general-purpose water-soluble fertilizer mixed at one-quarter strength. As they grow, transplant them into larger containers, handling them by the rootball or a leaf, never the stem.
Before moving plants outdoors, they need to be hardened off. The University of Minnesota Extension recommends placing seedlings outside for a few hours in the shade during the afternoon, gradually increasing their exposure to sun and wind over two weeks. By the end, they can stay outside unless freezing temperatures are forecast.
Planting Outside: Sun, Soil and the Petunia Example
Petunias are a popular annual that illustrates many key care steps. The University of Minnesota Extension’s petunia guide says to wait until soil warms to about 60 degrees Fahrenheit and frost danger has passed before transplanting. Petunias need at least 5 or 6 hours of good sunlight; they perform even better in full sun all day.
Prepare the soil by spreading 2 to 3 inches of organic matter such as compost and working it into the top 8 to 10 inches. The University of Minnesota Extension suggests incorporating a balanced fertilizer like 8-8-8 at a rate of 2 pounds per 100 square feet. For a recommendation tailored to your garden, have a soil test run through your local extension office. Before you dig any new beds or paths, contact 811 a few business days ahead to have underground utilities marked.
Space grandiflora and multiflora petunias about 12 inches apart in full sun. Milliflora types can be as close as 4 to 6 inches, while spreading ground-cover types need at least 1.5 feet. When grandifloras or multifloras reach about six inches tall, pinch them back to encourage side shoots. Do not pinch millifloras or spreading petunias.
Water thoroughly once a week for in-ground petunias, soaking the soil 6 to 8 inches deep. Spreading types and containers need more frequent watering. The University of Minnesota Extension notes that deadheading, removing faded flowers including the seed-forming part below each bloom, encourages more flowers and keeps plants looking fresh. For containers, incorporate a timed-release fertilizer at planting and then use a liquid fertilizer every two weeks. Our container gardening guide has more tips for pots and window boxes.
Seasonal Care: Dividing Perennials, Mulching and Planting Bulbs
The University of Minnesota Extension provides a home garden care calendar for the Upper Midwest. While your local dates will differ, the sequence of tasks offers a useful framework. The calendar lists a good time for dividing perennials as the second week of April through the third week of June, and again from the end of June through the end of August. Dividing keeps plants vigorous and gives you new plants for other areas.
Mulching beds is recommended from May through the end of June, and again from October through the end of November. A fall mulch layer helps protect plant roots over winter. For more on choosing and applying mulch, see our mulching guide. The calendar also suggests planting spring-blooming bulbs from the second week of September through mid-November. Other seasonal tasks include cutting back perennials in March and April, and planting annuals from late May through June. Always check with your own state’s extension service for local timing.
Designing with Pollinators in Mind
UMass Amherst Extension encourages gardeners to create pollinator-friendly landscapes. A diversity of plants, trees, shrubs, perennials, annuals, and even unmowed areas, supports a wide range of pollinators. Aim for a sequence of flowers from spring to fall. Straight species often provide more pollen and nectar than cultivated varieties, and double flowers may have less than single ones.
Plant in clumps or repeat species throughout the garden to help pollinators move between patches. Provide clean water sources such as a birdbath, shallow dish, or dripping faucet. Leave some bare soil for ground-nesting bees, and offer nesting materials like twigs, plant fibers, and fuzzy foliage. UMass Amherst Extension recommends using non-chemical solutions whenever possible. If pesticides are necessary, apply them in the evening when pollinators are least active and avoid spraying plants that are in bloom. Even a few pollinator-friendly plants in containers can make a difference; our pollinator garden ideas can help you get started.
A Simple Flower Gardening Checklist
- Choose a mix of annuals for quick color and perennials for long-term structure.
- Start annual seeds indoors according to packet timing, using clean containers and soilless mix.
- Provide 12 to 16 hours of light daily and keep lights close to seedlings.
- Harden off seedlings gradually over two weeks before planting outside.
- Prepare garden soil with organic matter and a balanced fertilizer; base amounts on a soil test.
- Wait until after the last frost and soil has warmed before transplanting tender annuals.
- Water deeply and regularly, and deadhead spent flowers to prolong bloom.
- Divide perennials during the recommended windows for your region.
- Apply mulch in spring and again in fall for winter protection.
- Plant spring-blooming bulbs in the fall.
- Include a variety of pollinator-friendly flowers and provide water and nesting spots.
- Contact 811 before any digging project.
Frequently asked questions
How do I know when to start seeds indoors?
Check the seed packet for the number of weeks before the last frost date, and look up your local frost date. The University of Minnesota Extension notes that many annual flowers are started in early spring in Minnesota, but timing varies widely. Your state’s extension service can provide the most accurate dates for your area.
Do I need to deadhead all flowers?
Not every flower requires deadheading, but removing spent blooms on many annuals, such as petunias, encourages more flowers. The University of Minnesota Extension explains that deadheading prevents seed formation and keeps plants looking tidy. It is especially helpful for container-grown annuals.
Can I grow flowers if I only have a balcony?
Yes, many annuals thrive in containers. The University of Minnesota Extension’s petunia guide points out that containers need more frequent watering and fertilizing than in-ground beds. For step-by-step setup advice, read our container gardening article.
For more flower gardening advice, explore our Flower Gardening section.
