WHEN TO PLANT BLACK-EYED SUSANS – PLANTING GUIDE 2021

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when to plant black-eyed susans

Black-eyed Susans are sunny, easy-to-grow plants that typically produce bright yellow or orange flowers with a black or brown center. There are two types, both of which thrive in the Midwest.

Rudbeckia hirta, which has a daisy like flower is native to North America while the black-eyed Susan vine, Thunbergia alata, is native to parts of Africa, so we are going to focus on Rudbeckia hirta.

When to plant black-eyed susan? Both types of black-eyed Susan plants are easy to grow from seeds and should be planted in spring, early summer, or in the fall when the soil temperature is between 60 and 70℉ (15,5-21℃). 

Planting Black Eyed Susans in Different Climates

planting black eyed susans in different climate

Both the U.S. and Canada have identifiable gardening zones that we can use when deciding which plants are suitable to grow where we live. Seed packets commonly state which zones are suitable growing areas. 

The United States Department of Agriculture (USDA) Plant Hardiness Zone Map has been an established standard for growers and gardeners since 2012. Canada’s Plant Hardiness Zone Maps do the same, and they follow the same principles of the USDA, using extreme minimum temperatures as a guideline.

The other more general guideline that gardens have is the internationally recognized Köppen climate classification system. This uses different criteria, including temperature, to indicate different climate regions based on local vegetation. 

The five basic zones are:

  1. Tropical, also sometimes referred to as equatorial
  2. Dry or arid
  3. Temperate, which is usually mild and warm
  4. Continental
  5. Polar, which is extremely cold

Zones are then subdivided further, based more specifically on dryness and temperature. 

In general, the American black-eyed Susan, which is commonly called the gloriosa daisy, will thrive in the USDA plant hardiness zones 3-9. The African black-eyed Susan vine does best in zones 9 and 10. 

Rudbeckia hirta is naturalized throughout most of the continental U.S. and southern Canada, but is native to the prairies and plains of the Midwest. The vine, which is an evergreen perennial, is often grown in the Midwest as a seasonal annual. So it is helpful to identify the typical Midwest climate where both types of black-eyed Susan plants thrive.

If your climate conditions are the same or similar, you’re in the right place to grow black-eyed Susans. 

The Climate of the Midwest

Here are some features to note:

  • Humid continental climate
  • Four distinct seasons
  • Weather conditions are usually gentle
  • Summers are pleasantly warm
  • Average high temperature 85℉ (29℃) 
  • Average low temperature 15℉ (-9℃) 
  • About 4 inches (10 cm) of rain every month in spring and summer
  • Between 3 and 6 feet (0.9-1.8 m) of snow in winter, depending on the area

Tropical Climate

Despite its humidity, the Midwest is not a tropical destination. 

In tropical climates, the average temperature in the coldest month of winter is no less than 64℉ (18℃). So it’s generally too hot for black-eyed Susans.

Dry Climate

Rudbeckia hirta does best with regular watering. Although it is a tough plant and will tolerate drought, in a dry climate, it is particularly important not to let the soil dry out. 

Temperate Climate

Some temperate climate conditions result in a dry summer while others experience a dry winter. Some mild temperate climates are humid. Remember that your American black-eyed Susans need water during the growing season, but you can sow seeds in spring or the fall. 

Generally, the average temperature in the coldest month of winter is warmer than 18℉ (-3℃). This is similar to the average low temperatures in the Midwest.  

Continental Climate

In line with the typical Midwest climate, a humid continental climate is ideal for Rudbeckia hirta and the Africa black-eyed Susan. 

Polar Climate

It doesn’t get any warmer than 50℉ (10℃) in summer, so, unless you have a greenhouse or heated growing tunnel, you won’t have any success growing either type of black-eyed Susan. 

Choosing Black Eyed Susan Seeds

Rudbeckia belongs to the daisy (Asteraceae) family. They include annuals, perennial varieties, and biennials. 

Often they are called “short lived perennials”, but it depends entirely on the seeds you plant and the growing conditions in your garden. Some will continue to grow for years and years, especially if you let them self-seed and propagate them by separating clumping roots. More on this later on. 

Ultimately, knowing what to look for will help you choose the right black-eyed Susan seeds for your garden

The USDA lists 48 Rudbeckia species, most of which are types of coneflower, and four of which are brown-eyed Susan, Rudbeckia triloba. 

They list Rudbeckia hirta (our American black-eyed Susan species) as well as four varieties with several variants. There are also some stunning Rudbeckia hirta cultivars that you will likely find at your local garden center or online seed stores. 

Colors and Types

These popular black-eyed Susan plants all have a daisy like flower that may be single, semi-double, and full-double in form. The sunny color range includes yellow orange, bronze, and gold. There are even some multi-colored blooms. 

Most have a long bloom period. They all make a lovely cut flower for the vase. 

One of the most popular species is Indian Summer, a gorgeous flower with 6-7.8 inch (15-20 cm) wide golden-yellow blooms. It first hit the wall of fame when it won the All-America Selections in 1995! 

Remember, you can also look out for gloriosa daisy seeds. That’s the black-eyed Susan’s most common name! 

How to Plant Black Eyed Susan Seeds

how to plant black eyed susans

Unless you are going to start seeds indoors, you will need to wait for the soil temperature to reach 70℉ (21℃) before you plant your American black-eyed Susan seeds. The African type can be planted when the soil temperature reaches 60℉ (15.5℃).

Like most easy-growing plants, they like moist, fertile, well-drained soil and prefer to be in full sun. Black-eyed Susans are not fussy plants and will grow in loam, clay, and sandy soils. If you have a soil test kit, check the pH – it prefers the soil to be acidic with a pH of less than 6.8.

Sow seeds directly in the ground and loosely cover with soil. Do not bury them in the ground.  

The American type will grow to at least between 1 and 3 feet tall (that’s about 30-90 cm). Each plant will spread to between 12 and 18 inches (30-46 cm).

How to Water Black Eyed Susans

Once you plant black eyed Susans, it’s important to check the seedlings regularly to make sure that the soil doesn’t dry out. Water thoroughly when you have planted them, then whenever necessary while they grow. 

A good rule of thumb is to give the plants about 1 inch (25 mm) of water every week. This will encourage the roots to spread but it won’t result in waterlogging them. If the soil is too wet, the roots of black-eyed Susan can rot. 

Once the plants are established you can relax on your watering regime. At this stage rather underwater your growing daisy like flowers. 

How to Grow Black Eyed Susans

Both types of black-eyed Susan plants are incredibly easy to grow. Plant them and leave them to it. But let’s talk about our American black-eyed Susans.

They will grow just about anywhere, and they need minimal attention. Some types need to be staked, others don’t. Check the package instructions. 

Another bonus about these lovely daisy-like flowers is that they make great cut flowers. 

If you pull out any plants, unless you want to get rid of them altogether, leave some of the roots in the ground. It’s a wonderful way to propagate new plants as they will eventually produce new plants. Alternatively, you can divide root clumps in winter when the plants have stopped flowering.  

If you don’t like the cut flower idea, remember that many gardening experts recommend deadheading the flowers to prolong blooming. But don’t prune them while the leaves are green. They are still photosynthesizing and building up carbohydrate reserves, so leave them to build up potential energy and nutrients for next year’s flowers. 

It is also a good idea to leave some dead heads on the plants because they will self-seed. The birds will also have a feast, so you’ll be doing your bit for nature! 

Pests and Diseases

Apart from the usual slugs and snails, aphids, and rust, black eyed Susans are not susceptible to any major insect or disease pests other than powdery mildew. A fungal disease that affects many different plants including pumpkin, squash, tomatoes, pepper, beans, and peas, it spreads in the wind. 

Powdery mildew is a common problem in warm, dry climate conditions but spreads more rapidly when it is humid. It affects plants in shady areas rather than those growing in full sun. 

You can prevent and treat powdery mildew with different types of fungicides. If you want to avoid using chemicals, mix 1 teaspoon of baking soda (bicarbonate of soda) into a quart (950 ml) of water and spray the plants well. 

If your black-eyed Susans are heavily infected, it’s best to dig them out and destroy them. Don’t ever use infected plants in a compost heap. 

How Long Do Black Eyed Susans Take to Grow?

It takes American black-eyed Susan seeds anything from 7 to 30 days to germinate. But most commonly, in warm spring and summer weather conditions, they will germinate in the soil within 10 days. 

Conclusion

We’ve talked about two types of black eyed Susan plants, one that is native to North America and one that originated in parts of Africa. 

We have, though, focused on our own American species, Rudbeckia hirta. It’s an easy-to-grow plant that produces stunning daisy-like flowers in bright yellow, orange, and other similar hues. 

This gorgeous black-eyed Susan is perfect for humid continental climate regions but will grow just about anywhere if given the chance. Why don’t you give it a chance in your garden?

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