Greenhouse plants do not need to be strictly food crops or medicinal plants, consider adding some beauty for your own enjoyment! What’s blooming in your greenhouse? In this post we discuss a few ornamental plants to grow in your greenhouse: African marigolds, cosmos, dahlias, salvia, snapdragons, zinnias and other cut flowers.
Some of the benefits of growing ornamental plants in a dome greenhouse are an extended growing season, the ability to control the climate and fewer pests to deal with.
Greenhouse atmospheres are inviting to pests, too. They are more likely to be insects as rodents, raccoons, deer and other large mammals may not be able to get into a greenhouse.
Check your soil annually or semi-annually. We recommend testing in the spring or fall. Without outside influences a greenhouse can be prone to pH or nutrient imbalances.
Let us know your favorite ornamentals!
What’s Blooming in Your Greenhouse? African Marigolds!
- Family: Asteraceae
- Botanical Name: Tagetes erecta
- Common Name: African marigold, Mexican marigold, Aztec marigold, marigold
- Type: Annual
- Light: Full sun
- Soil pH: Acidic, neutral
- Zone: 2-11 (USDA)
- Size: 1–4 ft. tall, 1–2 ft. wide
Note: African Marigold flowers and sap are mildly toxic to humans.
Marigolds are always a great addition to the garden. They help repel pests and attract pollinators. African marigolds can grow up to 4 feet tall.
Caring for Marigolds
Marigolds need full sun and can grow well in many types of soil. They need one inch of water per week and can handle hot, dry conditions. Marigolds do not tolerate frost or cold.
Encourage your marigold to grow fuller by pinching the tips of young plants. If not, the plant may grow tall and top heavy. Trim or deadhead plants regularly to encourage more flowering throughout the season.
Marigold Pests and Diseases
African marigolds are not as likely to suffer from pest damage, watch for damage from Japanese beetles, red spider mites, slugs and snails. Insecticidal soap works wonders against these invaders.
Avoid wetting foliage while watering, especially in late afternoon. Wet leaves are prone to powdery mildew and other types of leaf damage or root rot. Water soil early in the day and keep the leaves dry.
Good air circulation will help to prevent some diseases.
Some varieties of marigolds have a chemical that emits through the roots. This can be helpful in fighting some types of soil nematodes that are destructive in the garden. French marigolds (T. patula) are more likely to have this chemical than African marigolds.
Marigolds attract quite a few pollinators, which is great for greenhouse gardens. These include bees, butterflies and lady bugs.
Some garden websites give marigolds credit for repelling garden pests.
History and Trivia of Marigolds
African marigolds are native to Central and South America. They arrived in Europe via African ports, hence the name African Marigolds.
Marigolds are known as cempasúchil (Pronounced: sem-pa-soo-cheel) in Nahuatl, the ancient language of the Aztecs. Cempasúchil means flower with twenty petals.
The world’s largest marigold producers are China, Peru and India. The biggest importers of marigolds are Europe and the United States.
Did you know the marigold symbolizes beauty, creativity and warmth?
Marigolds are symbolic in Day of the Dead celebrations and used to decorate gravesites and home altars.
A cultural symbol in Nepal, marigold garlands can be found in many Nepalese homes.
What’s Blooming in Your Greenhouse? Cosmos!
- Family: Asteraceae
- Botanical Name: Cosmos sulphureus, Cosmos bipinnatus
- Common Name: Cosmos, Mexican aster
- Type: Annual
- Light: Full sun
- Soil pH: Acidic
- Zone: 2-11 (USDA)
- Size: 1-6 ft. tall, 1-3 ft. wide
Beautiful cosmos are incredibly easy to grow and will self-seed. They look similar to daisies and come in a wide variety of colors. They will attract bees and butterflies to your dome greenhouse and garden.
Caring for Cosmos
These plants are drought tolerant, not particular about soil and do well even when neglected. Cosmos tolerate some shade, but if you want a plethora of flowers, plant them in full sun. Deadheading spent flowers will lead to more blooms.
Cosmos will grow too fast if the soil is rich. They may require a trellis or stakes to stay upright. Grow them along a fence for support.
Cosmos need to be watered more frequently during extended drought periods. Overwatering can lead to fewer flowers.
Cosmos Pests and Diseases
Aphids, thrips and flea beetles like cosmos. Using insecticidal soap or spraying water can usually solve the issue. It’s always a good idea to keep close tabs on your plants! Don’t forget to check the undersides of leaves.
Good air circulation is vital to healthy plants so thin your flowers! Water the soil rather than the plant in order to avoid powdery mildew.
History and Trivia of Cosmos
Cosmos are native to Mexico and are found in scrub and meadowland. There are over 30 varieties of cosmos.
Spanish explorers from Madrid introduced these beautiful flowers in the 16th century.
Cosmos are found in the Olympic Peninsula of Washington state and as far south as Paraguay.
Cosmos are symbolic of peace, innocence and luck. October’s birth flowers are cosmos and marigolds.
Did you know that the Greek word kosmos means “orderly arrangement”? Cosmos flowers are uniform and orderly.
What’s Blooming in Your Greenhouse? Dahlias!
- Family: Asteraceae
- Botanical Name: Dahlia spp.
- Common Name: Dahlia
- Type: Perennial (Zones 8 and higher), Annual (Zones 7 and lower)
- Light: Full sun
- Soil pH: Neutral, acidic
- Zone: 8-10 (USDA)
- Size: 1-6 ft. tall, 1-3 ft. wide
Note: Dahlias are toxic to dogs, cats and horses.
Do you love having flowers of all colors in your dome or garden? Dahlias are amazing! They range in size from lollipop size to dinner plate size. Some are even variegated and bi-color.
Caring for Dahlias
Plant dahlia tubers when the soil temperature is 60 degrees F (15 degrees C) or above. They will not tolerate cold soil or frost. .
Once the tubers sprout, water them weekly. Water them more during drought periods. Deadheading faded flowers may increase new blooms.
Dahlias prefer full sun with a minimum of 6-8 hours of sunlight per day. Protect them from hot afternoon sun by giving them some shade.
They need warm soil and are considered a late summer crop. Dahlias can bloom until the first frost.
Dahlia Pests and Diseases
Unfortunately, there are some pests that just love dahlias. Caterpillars, earwigs, and slugs will feast on them if possible. Deal with slugs in the sprouting stages of a dahlia’s growth or they will wreak havoc.
Deer can be a problem for gardeners. Be sure not to leave the greenhouse door wide open!
Dahlias struggle with powdery mildew. Air circulation and watering techniques can help to prevent it.
History and Trivia of Dahlias
Spanish botanists reported about these beautiful plants growing wild on the hillsides of Mexico back in the 1500s.
The dahlia is the national flower of Mexico. They represent beauty, elegance and creativity in Mexican culture.
Did you know that dahlia coccinea was introduced to the Royal Botanic Gardens in Madrid from Mexico back in 1789?
Some dahlias varieties were originally grown as a food crop. According to Gardeners television presenter James Wong, the tubers taste like a cross between carrots, celery and potatoes.
In Europe and America some diabetics were given a substance called Atlantic starch which helped control blood sugar. This was made from dahlia tubers!
What’s Blooming in Your Greenhouse? Salvia!
The genus salvia has hundreds of species and is commonly known as sage. In many instances “salvia” is used for ornamentals and “sage” refers to the culinary plant. Hummingbirds, butterflies and bees love salvia or sage or whatever we call it!
- Family: Lamiaceae
- Botanical Name: Salvia spp.
- Common Name: Sage, salvia, garden sage, common sage
- Type: Flower
- Light: Full sun
- Soil pH: Slightly acidic to neutral
- Zone: 5-10 (USDA)
- Size: Height – 3-6 ft.; Spread – 12-48 in.
Caring for Salvia
Salvia needs 6 hours of sunlight per day and can tolerate some shade. Too much shade will make it leggy and lead to fewer flowers.
Well draining soil is important for growing salvia. The best plan for watering salvia is to let the soil dry completely between waterings.
Too much water can lead to fungal diseases. Salvia does just fine with brief periods of drought.
Deadheading and pruning your salvia throughout the growing season will help keep your plants beautiful.
Salvia Pests and Diseases
Salvia is fairly pest resistant, but can attract aphids, spider mites and whiteflies.
One of the benefits of growing salvia in your garden is that te pungent odor deters deer, rabbits and other pests.
Diseases to be aware of for salvia are: botryris, powdery mildew and root rot.
History and Trivia of Salvia
Botanist George Bentham was the first to give a full account of the salvia plant between the years of 1832-1836.
There are over 900 species of this genus. Central and South America have the most with approximately 600 species. Central Asia and the Mediterranean have about 250 species. Eastern Asia has 90 species.
Salvia is commonly called “sage”. No matter what name you use, it has many benefits for your garden and greenhouse.
The reason sage is drought tolerant is two-fold. They have aromatic oils and tiny hairs on the leaves. Both of these attributes help to minimize water loss.
Did you know that sage tea is used to soothe sore throats, helps with digestion and there’s something else it does….oh, right, it helps with memory and focus!
Salvia or sage is a beautiful addition to the garden as it helps deter pests and adds color. Just pick your favorites: blue, pink, purple, red and white!
The aroma of the sage plant itself repels deer and rabbits.
What’s Blooming in Your Greenhouse? Snapdragons!
- Family: Plantaginaceae
- Botanical Name: Antirrhinum majus
- Common Name: Snapdragons, dog’s mouth, lion’s mouth, toadflax, dog flower
- Type: Perennial, annual
- Light: Full, partial sun
- Soil pH: Acidic, neutral
- Zone: 7-11 (USDA)
- Size: 6–48 in. tall, 6–12 in. wide
Snapdragons are a favorite garden flower of many gardeners. The height and shape draws attention. Plus they have a large variety of colors.
Caring for Snapdragons
These flowers do well in partial shade and prefer rich soil. If you pinch the tips of young plants, they will grow bushier which will make for a sturdier plant.
Snapdragons are a cool season crop and may stop blooming if they are too warm. Plant them near the pond in the dome where they will stay cooler. They prefer temperatures between 40 – 70 degrees Fahrenheit.
As young plants they require more frequent watering. Once established they need an inch of water per week. They may need more water in times of drought. Allow the first inch of soil to dry before watering again.
Snapdragon Pests and Diseases
Common problems with snapdragons are aphids, spider mites, rust fungus and mold issues. Watch for whiteflies and caterpillars that dine on foliage. We recommend keeping insecticidal soap and neem oil on hand.
In the case of rust fungus, consider planting snapdragons in a different location for the next season. Remove and dispose of any leaves by burning, burying or rapid composting.
Snapdragons attract beneficial insects, are deer resistant and increasing in popularity with their cottage charm.
History and Trivia of Snapdragons
Snapdragons are native to southern Europe. They are commonly found in Canada, the United States and North Africa.
A natural “beautifier” it has been known to “escape” from gardens. It is sometimes found meandering into roadsides as well as dumps and waste areas.
Did you know that the name snapdragon comes from the Greek word “antirrhinum” or calf snout?
Haven’t we all squeezed a snapdragon flower (or like 20) to open the “dragon’s” mouth?
In 1767 Thomas Jefferson noticed snapdragons blooming at his childhood home. Four years later he later listed them “to be naturalized in a shrubbery” at his home in Monticello.
Snapdragons symbolize grace and strength.
Did you know that snapdragons are pollinated mostly by larger bumblebees? The smaller honeybees cannot open the snapdragon’s mouth!
What’s Blooming in Your Greenhouse? Zinnia!
- Family: Asteraceae
- Botanical Name: Zinnia elegans
- Common Name: Zinnia
- Type: Annual
- Light: Full sun
- Soil pH: Acidic, neutral, alkaline
- Zone: 2-11 (USDA)
- Size: 1-3 ft. tall, 8-12 in. wide
Zinnias are a flashy beauty to add in your dome, attract butterflies and require minimal care. They are great as cut flowers to share in your home.
Caring for Zinnias
Colorful zinnias need full sun or a minimum of 6 hours of sun daily. They thrive in heat and can grow to 3 feet tall. They can provide shade for plants that need shade for protection from afternoon heat.
Zinnias prefer well draining soil and are drought tolerant. This means less watering for you! Remember to consider what water requirements their neighbors may need.
If you plant them from seed, be strong and thin them as seedlings! This is important as they need air circulation and this is very helpful in avoiding powdery mildew.
Zinnia Pests and Diseases
We enjoy the beauty of zinnias, but caterpillars, mealybugs, and spider mites enjoy eating them!
Spend time thoroughly checking your plants. For tips on dealing with pests, visit our website blog!
Monitor zinnias for diseases such as powdery mildew, bacterial and fungus. Avoid wetting the foliage when watering to eliminate some of the causes of those diseases.
One of the most challenging aspects for gardeners is to give plants enough space for quality air circulation. We all need to practice thinning our plants. No matter how hard it is to pull those extra little seedlings, do it! Your plants will be healthier and thank you.
If you have beds on the outside of your dome and have deer in your area, consider adding some zinnias to the beds. They are deer resistant and discourage the deer from eating other plants in your outdoor beds.
History and Trivia of Zinnias
Native to Mexico, zinnia was named for German botanist Johann Gottfried Zinn.
Did you know that zinnias were used by the Aztecs in ceremonial rituals?
According to the Victorian language of flowers, zinnias symbolize missing friends.
Zinnias were one of the first flowers to be grown in space in 2015! They were grown as an experiment on the International Space Station. Dr. Gioia Massa, a Nasa Veggie Project Scientist, explained that “Flowering is really important for fruiting crops, such as tomato which we hope to grow in the next couple of years because you have to have flowers before you produce fruit.” (Quote at 3:46 on the video.)
Cut Flowers
Do you enjoy having fresh cut flowers in your home? Plant some in your greenhouse!
Along with flowers for your cut flower garden, include ferns, herbs and other greenery to accent your bouquets. Did you know you can use carrot tops for the greenery in your flower arrangements?
Below are some suggestions for a cut flower garden. Consider size, water and companion planting when choosing flowers and plants for a cut flower garden.
Note: Some flowers and plants are toxic to dogs, cats and horses. The ASPCA has a toxic plant list on their website.
Spring flowers:
Bearded Iris (Toxic to dogs, cats and horses)
Daffodil (Toxic to humans and pets)
Tulips (Toxic to humans and pets)
Summer flowers:
Black Eyed Susan
Dahlia
Shasta daisy
Sunflower
Yarrow
Zinnia
Fall flowers:
Asters
Garden mum
Globe Amaranth
Russian Sage
Winter flowers:
This depends on what zone you live in and /or if you heat your dome greenhouse.
Lenten Rose
Winter Jasmine
We hope you enjoyed this article about growing ornamental plants and consider adding some to your greenhouse. Happy gardening!
