Cold Hardy Annuals – Growing Annuals In Zone 4
While zone 4 gardeners are used to having to select trees, shrubs, and perennials that can withstand our frigid winters, the sky’s the limit when it comes to annuals. By definition, an annual is a plant that completes its entire life cycle in one year. It germinates, grows, blooms, sets seeds, and then dies all within one year. Therefore, a true annual is not a plant you have to worry about overwintering in cold climates. However, in zone 4 we tend to grow other, less hardy plants like geraniums or lantana as annuals even though they are perennials in warmer zones. Continue reading to learn about growing annuals in zone 4 and overwintering frost sensitive plants in frost prone areas.
Cold Hardy Annuals
“Annual” is a term we use a little loosely in cool climates for basically anything we grow that cannot survive outdoors in our winters. Tropical plants like cannas, elephant ear, and dahlias are often sold as annuals for zone 4, but their bulbs can be dug up in autumn to be dried and stored indoors through the winter.
Plants that are perennials in warmer climates but grown as zone 4 annuals may include:
However, many people in cold climates will simply take these plants indoors through winter and then place them outdoors again in spring.
Some true annuals, like snapdragons and violas, will self-sow. Although the plant dies in fall, it leaves behind seeds that lay dormant through winter and grow into a new plant in spring. Not all plant seeds can survive the cold winters of zone 4 though.
Growing Annuals in Zone 4
Some important things to know about growing annuals in zone 4 is that our last frost date can range anywhere from April 1st to mid-May. For this reason, many people in zone 4 will start their seeds indoors in late February to mid-March. Most zone 4 gardeners do not plant their gardens or set annuals out until Mother’s Day or mid-May to avoid damage from late frosts.
Sometimes you just have spring fever though and can’t resist purchasing those lush baskets that stores begin to sell in early April. In this case, it’s important to keep an eye daily on the weather forecast. If there is frost in the forecast, move annuals indoors or cover them with sheets, towels, or blankets until the danger of frost has passed. As a garden center worker in zone 4, every spring I have customers who plant annuals or vegetables too early and lose almost all of them due to late frosts in our area.
Another important thing to keep in mind in zone 4 is that we can begin to have frosts in early October. If you plan to overwinter frost sensitive plants indoors through winter, start preparing them in September. Dig up canna, dahlia, and other tropical bulbs and let them dry out. Put plants like rosemary, geranium, lantana, etc. into pots that you can easily move inside as needed. Also, be sure to treat any plants that you intend to overwinter indoors for pests in September. You can do this by spraying them with a mixture of dish soap, mouthwash, and water or by simply wiping all surfaces of the plant with rubbing alcohol.
The short growing season of zone 4 also means that you must pay attention to “days to maturity” on plant tags and seed packets. Some annuals and vegetables must be started indoors in late winter or early spring so they will have enough time to mature. For example, I love Brussels sprouts, but my one and only attempt to grow them failed because I planted them too late in spring and they did not have adequate time to produce before an early autumn frost killed them.
Don’t be afraid to try new things. Many beautiful tropical plants and zone 5 or higher perennials can be grown as annuals for zone 4.
The Best Perennials for Pollinators
Bring a biodiversity of insects to your pollinator garden by choosing native plants with different flower colors, shapes, sizes, and blooming periods. Also plant flowers in groupings, which are more enticing to pollinators than single plants. Photo by: Anne Balogh. Pollinator patch planted by the second grade students at Abraham Lincoln Elementary School, Glen Ellyn, Ill.
When was the last time you saw butterflies flit through your flowers or heard the drone of bumblebees? If your garden has become a ghost town rather than a hive of activity, you’re not alone. One of the major reasons for the dwindling pollinator population is habitat loss. Butterflies, bees, and other important pollinators are becoming rare sights in many residential gardens across the country due to the widespread use of pesticides and a dwindling supply of the nectar-rich flowers they rely on for food. Fortunately, you can play a role in reversing this trend by devoting a spot in your garden to pollinator-friendly plants and keeping local pollinators well fed year-round.
“Small plantings may seem insignificant to you, but if each yard devotes a small area to pollinators, your neighborhood will serve as a season-long buffet of nectar and pollen that supports a diversity of bees, butterflies, and other flower visitors. If you do not have the yard space, you can fill a decorative planter with pollinator-friendly plants and place it in a sunny spot on your patio or stoop,” says Kelly Gill, pollinator conservation specialist for The Xerces Society. (Read her article "Everyone Can Play a Role in Pollinator Conservation".)
Zone 4 is one of the shortest growing seasons of the USDA zones. The first and last frost dates can fluctuate a week or two, but as a general rule, frost dates are used for zones to plan garden planting.
Frost dates for Zone 4 last and first frosts for the year are typically:
- Last frost date:May 15 to June 1 is usually the last frost range for Zone 4.
- First frost date: September 15 to October 1 is usually the first frost range for Zone 4.
To stay current on frost warnings, download a frost date app. All you have to do is enter your zip code to access your regional timeframe.
Proven Winners ® Annuals—WOW power! for landscaping and containers
Annuals are the flower power behind every gorgeous garden, hanging basket and patio pot. They are showy, easy-to-grow favorites of both new and experienced gardeners. And when you choose Proven Winners ® annuals, you can count on having big beautiful blooms all season long with minimal care.
Choose from hundreds of Proven Winners ® annuals specifically developed for their summer garden performance and these characteristics:
• Easy care
• All-season bloomers
• Covered in bright colorful blooms
• Disease free
• Trialed and tested for proven performance
Keep in mind not all flowering plants are annuals, some are perennials. The difference is annuals are one-season plants that die when it gets cold. You replant them every year. Perennials appear to die when the temperatures drop, but their roots are actually hibernating and will produce new plants in the spring. With annuals you start with a new plant palette every growing season.
10 Easiest Annuals to Grow
- Supertunia ® Vista Bubblegum Petunia hybrid
- Butterfly Argyranthemum frutescens
- Luscious ® Berry Blend ™ Lantana
- Sweet Caroline Ipomoea batatas
- Graceful Grasses ® Vertigo ® Pennisetum purpureum
- Snow Princess ® Lobularia hybrid
- Colorblaze ® Solenostemon scutellarioides (Coleus)
- Sénorita Rosalita ® Cleome hybrid
- Diamond Frost ® Euphorbia hybrid
- Graceful Grasses ® King Tut ® Cyperus papyrus
Choose plants that reseed themselves for years of bloom. Here’s our list of 20 annual and perennial flowers that are self-sowing. And if you are busy deadheading your flowers—stop! Take a look at the seed heads you are cutting off. Towards late summer, allow some of the seed heads ripen until they turn brown and split open.
Your Self-Seeding Garden
The seed heads of plants are like salt shakers full of tiny seeds. When the capsules split open, scatter the seeds anywhere you would like them to grow or just let them drop where they are. Next spring, keep a sharp eye out for the seedlings when weeding. Some may be slow to emerge. If there are more than you want you don’t have to keep them all. Thin them out to allow enough space for the plants to fully develop. Relocate the extras or pot them up to share with friends.
Don’t be surprised if nothing germinates in the fall. Some seeds just don’t like hot soil and others, such as poppies, need a cold period before they will sprout. This is called “vernalization.” Wait until spring to look for your seedlings.
If you live in a warm region, some of your scattered seeds—the ones that don’t mind the heat and don’t need a cold period—may sprout and grow during a mild winter. They will flower early and set more seeds, giving you several generations a year.
Open-pollinated and heirloom flowers will look like the parent plant, while hybrids usually don’t stay true to seed. Keep an eye out for “sports”—chance seedlings that display attractive traits not found in the parent plant. These genetic mutations can lead to some interesting new forms of old favorites.
This maroon Belamcanda was a pleasant surprise. All the others were orange! We will definitely save the seeds from this sport.
Self seeders will give your garden a natural, cottage garden look but some of them can become nuisances, crowding out more desirable plants. Be prepared to thin them out or move them to other spots around your yard.
Self-Sowing Annual Flowers
Here are some annuals that are willing self-sowers:
Colorful calendula are eager to self-sow. Bees and butterflies love them!
- bachelor buttons
Biennials rely on self sowing to keep the population going. They form a leafy plant in year 1 and will blossom in year 2:
These foxglove seeds are ripe and ready to fall.
Self-Sowing Perennial Flowers
Many perennials will self-seed if not deadheaded:
- New England asters
Columbine seeds are ready to be shaken out wherever you want them to grow.
Save a little money on plants next spring by welcoming some volunteers to your garden.
Common questions about planting calendars
Can there be more than one planting season?
Some zones offer succession planting, or “second plantings.” Warmer climates, such as zones 7 – 10, will often provide two opportunities to plant some of your favorite veggies. For example, in Florida, you can plant peppers and tomatoes in February to enjoy a summer harvest, and then again in early fall for a winter harvest.
How to tell how much to water your garden?
A good rule of thumb is to water your garden about 2 inches each week. Use this guide very loosely, though, as specific plants, zones and planting areas will all dictate how much water is actually needed. The water needs of one plant versus another can vary tremendously.
When is the best time to plant a garden?
There really isn’t any one, good answer to this question. Just like water, soil, light and other growing conditions, plants can have very different needs for the best time to be planted. The only way to know for sure is to use a gardening calendar that calculates the first expected and last average last frost date in a specific zone – this will help determine planting timing for each plant.
What can I plant before winter?
Just because the weather is cooling off doesn’t mean the growing season has to be over. Cooler fall temperatures are the perfect time to plant many delicious vegetables such as garlic, asparagus, peas and onions and shallots.
When should I stop watering before harvesting?
For most plants, stop watering about 1 -3 days prior to harvest. Ideally, soil should be relatively dry, but plants should not be so thirsty they wilt or droop.
Planning a gardening calendar is exciting – and a planting calendar takes some of the guesswork out of the process, so it can also be fun and rewarding. With careful thought, the end result is an entire garden of gorgeous plants that will produce all season long.