Flowery Lawn
May 18
There are several advantages in transforming a traditional lawn to lawn with flowers, especially at the ecological level, by maintaining a diversity of insects and beneficial organisms such as pollinators and predators, birds, by the increased soil biological activity, and by the decrease or complete cessation of pesticide use.
Moreover, such development requires little or no fertilizer and the presence of various plants retain more soil moisture, thus little or no watering.
Flowered lawn requires no mowing, or very little, depending on the height and number of varieties of plants incorporated (eg, a mixture solely of clover and grass versus a meadow of flowers). When there is a wide variety of plants, one mowing once a year in the fall, may suffice. Also, the children’s interest in nature could grow because they have at hand several plants and insects to know and identify compared to a conventional lawn.
One can begin by transforming a small area only. Thus, we take the time to observe the evolution of plants, see the benefits and improve the development, if applicable. The choice of plants is done according to our tastes and location on the ground (slope or flat land, location in full sun or partial shade, hardiness zone, etc..).
We can sow a mixture of grass seed, annuals (worries, carnations, cosmos, sweet peas, marigolds, etc..) And perennials (yarrow, rudbeckia, daisies, lilies, clover, etc..). You can also transplant some perennials here and there and plant some perennial bulbs (glory of the snow – Chionodoxa luciliae, crocus, star of spring – Ipheion uniflorum). Finally, one can simply let nature take its course through the establishment of native species and wild, checking them, if necessary.
** Note that some wild plants can be invasive (dandelion, hawkweed, forget-me). It will in this case the monitor and hamper expansion by eliminating a few plants, as they emerge, and this, by tearing their roots or the mowing before seed maturation.
Giant Hogweed- Beware
May 10
This beautiful giant may indeed be the cause of severe dermatitis on people who manipulate. This is why it is now recommended to avoid the transport or even to cultivate it, and get rid of safely if it grows on your property. There would be only few specimens in Canada, our producers have ceased to multiply for several years. Despite this, it is still possible to obtain seeds or roots.
High of 2.75 m and 1.25 m wide, giant hogweed (Heracleum mantegazzianum, syn. H. giganteum) is characterized by its large umbels of white flowers in summer, its leaves glossy green and deeply cut and toothed strong waxy stems splashed with purple. This herbaceous biennial hardy to zone 3 grows in sun or light shade.
The Ministry of Sustainable Development, Environment and Parks considers giant hogweed as an invasive alien plant (it was introduced in Canada and listed in 1990) and provides advice to get rid of. See fact sheet on giant hogweed.
The Union St. Lawrence Great Lakes announced a few months ago starting the monitoring network of invasive alien plants. Appealing to the public, the network is designed to quickly identify invasive species and to intervene at the earliest.
Carnivorous Plants Care
May 02
Carnivorous Plants Temperature
Those of tropical origin are well adapted to temperatures of our homes during the year. Others must spend the winter in a cool place where the temperature near 5 to 10 ° C. Remember that at that time, many of them will lose their foliage in whole or in part and appear dead, or almost. Do not panic: they will be reborn from their base after three or four months, when the air warms. It will now simply remove the brown leaves.
Insects and Diseases
Insectivores defend themselves well against insects (they devour them!) And are not very prone to disease, provided to ensure proper ventilation and remove any dead leaves. The blackening of the leaves is especially symptomatic of an excess of minerals rather than the presence of disease. Generally confined to a terrarium, they are not very effective to control insects that invest your other houseplants.
Multiplication
Once you know how to properly maintain your plants and keep them in good condition, you will enjoy multiply by division, cuttings or even seed …
Flowering
Without exception, better remove any flower stalk emerging: the flower is often irrelevant and the process of flowering unnecessarily consumes the energy of the plant.
Dione flycatcher (Dionaea muscipula)
The most popular indoor plants insectivorous, probably because of its remarkable trap, so quick to react. It develops a rosette smooth leaves, each ending in a toothed jaw. Green when exposed to partial shade, she blushed under the sun. When an insect touches the hairs at its center, or if you touch it with insistence, the trap closes. But beware, this is not a game: if it suffers too many false alarms, the trap dries. The plant seldom live long in our homes, because it requires full sun and a cold winter.
Rossoli (Drosera sp.)
There are many species of Drosera, some cold climate such as D. rotundifolia of our bogs. For a culture within, we prefer a tropical variety as D. adelæ or D. spathulata. The leaves are sometimes narrow, sometimes almost round, sometimes spatulate, but always covered with tiny hairs, all topped with a dab of glue that holds shiny insects. The sundew tolerate medium light but are more attractive to the sun. Even tropical species like cooler night temperatures in winter (10 ° C).
Butterwort (Pinguicula sp.)
Butterwort tropical (P. moranensis) is among the best suited for indoor growing: it tolerates our ambient temperatures even in winter, is going very well from full sun and does not require culture under glass. The soft green fleshy leaves form a dense rosette and appear covered in oil, hence the name “chubby”. Small insects, including fruit flies, are doing it and are digested slowly. This is a rare insectivorous we may be allowed to flower. The purple flowers bloom several times a year and reminiscent of a wild violet.
Some types of traps
Glue-flies
The plant secretes a sticky substance which adheres to the prey (rossolli).
Wolf trap
Leaves with two lobes close like jaws and trap prey (Venus Flytrap flycatcher).
Pit
The urn-shaped leaves contain nectar that attracts and retains the prey (Pitcher Plant).
Lobster traps
The leaves in closed tube at the base only open inwards. Once the prey into the tube, it can not get out (pitcher plant parrot).
Mousetrap
Small cavities are closed by a door that is activated when an insect touches the hairs located around the perimeter (bladderwort, water plant).
Grow Orchids
Mar 22
Today, orchids are available everywhere at reasonable prices, and they usually flower longer, even for several months. But how to successfully make them bloom again? Here’s a question for many gardeners .
Start with an orchid in bloom already. This ensures at least that its old enough to flower (most seeds produced by orchids take 5 to 7 years before they get there). Also make sure that your choice can adapt to your growing conditions.
The easiest orchid to grow in the house is the Phalenopsis (Phalaenopsis), also called butterfly orchid, since it tolerates moderate light and warm temperatures in our homes. If you plan to place your orchid in direct sunlight, you should choose a Dendrobium (Dendrobium) or one of many hybrids of Cattleya (Cattleya).
Light
The orchids are no different from other indoor plants in terms of their staple crop. If you are able to do an African violet bloom, for example, you should have no difficulty with an orchid. So you need a very good natural or artificial lighting, a window facing east for a Phalenopsis, south or west for a cattleya or dendrobium. In summer, you should remove the plants from the windows to put them further into the room. In winter, use a humidifier, because these plants require good humid air in our homes.
Watering
Watering orchids is a bit annoying because they do not grow in regular potting soil, but in a very special ventilated blend. However, the method for determining when to water remains the same as for any houseplant: insert your finger into the mixture, if it is dry, you water. According to the conditions and the season, it may be necessary to water an orchid from five days and up to two weeks! Water slowly pouring warm water over the mixture. You can add a fertilizer to irrigation water in spring and summer.
Flowering
Most orchids need cold to flower. In general, a temperature drop in the fall, 10 to 15 ˚ C at night, is enough. Failing to ensure this drop in temperature in the house, you can put the plant outside in the shade for a few days in the fall. Normally an orchid bloom again with the same period every year. So if you bought your plant flowers in spring, you should see a new flower stem to about this time next year.
Repotting
Orchids may remain several years in the same soil. However, over time, it will begin to decompose and must be replaced.Withdrew the plant, knock off the old soil and trim any rotten or dried root, then repot in a mixture sold specifically for orchids. Do not worry about the roots coming out of the soil, it is quite normal for orchids produce aerial roots. By cons, when you repot, you can cover them in part with the new mixture.
Flowers for Valentine’s Day
Feb 08
You let yourself be touched by Cupid’s arrow? Monday, February 14, celebrate your valentine or valentine with a gorgeous bouquet of love!The red rose, emblem of passionIt remains the essential flower to declare your love to beloved ones. Want to offer a bouquet of roses, but you’re not sure the number of stems. It is customary to present an odd number of roses when they are below 10. Beyond that, it’s more the gesture and the message that counts.
But here are some ideas:
1 pink = love at first sight
2 Roses= mutual love roses
3 Roses = I love you
9 Roses = eternal love, we will be together throughout life
11 Roses = You are my treasure, the one / the one I love most in the world
13 roses = secret admirer
20 Roses = I am honest with you
40 pink = my love for you is sincere
50 roses = love without regret
99 Roses = I will love you until the end of my life
108 Roses = marry me
The flowers gather beauty, finesse, delicacy, strength and sensitivity and can express so many feelings. Budding romance, love shy, exclusive and passionate love … anything goes with the flowers. Roses are traditionally associated with Valentine’s Day, but other very pretty red flowers are also perfect, gerbera, tulip, Santini, carnations, Alstromeria the example. A flower … a moment of happiness. Test and see!
Love is written with flowers, passion flower petals … you get the ingredients, you continue this recipe!
Grape Hyacinths
Dec 02
One of the best ways for gardeners to chase away the winter blues is with the blue grape hyacinths. A spring flowering bulb, it is planted in the fall. Although considered a “minor” bulb, being shorter and less common than daffodils and tulips for instance, it contrasts well with most other bulbs, and is striking when planted in masses.
Grape hyacinths are so named because their dense flower stalks, usually about 6 inches high, are comprised of many small flowers (florets) resembling grapes. Their scientific name (Muscari) comes from the Latin word for musk, referring to their slight scent. Depending on the species, they come from the Asia Minor region and all around the Mediterranean. While some selections were made in the last decade, the oldest in cultivation date back 400 years or more.
While there are over 40 species, generally less than 10 and their cultivars (cultivated varieties) are found in catalogs and stores. Grape hyacinths are related to other spring bulbs such as hyacinths, squill (Scilla), and striped squill (Puschkinia). Formerly in the lily family, these are now placed by botanists in either the hyacinth or asparagus families. 
The various grape hyacinths generally are placed into one of 4 groups, with some botanists considering one or more of these as different genera. The Leopoldia group is one of these, with taller plants (8 to 12 inches high), and florets spaced less densely along the stems. Florets are urn-shaped, flower in late spring, and are in colors other than blue. One species (comosum ) commonly found in this group, the tassel hyacinth, is one of the oldest introductions dating back to 1596. It has dark purple florets, while the related ‘Plumosum’ feather hyacinth cultivar dating to 1612 has feathery plumes of reddish violet.
The Pseudomuscari group is another that some consider a separate genus, comprising species that are small, often pale to bright blue, and flowering in early spring. Florets of this group are an open urn shape. A more common species in this group (azureum) was introduced in 1859 from the alpine meadows of eastern Turkey.
The Muscarimia group has one of the oldest species (muscarimi), introduced to cultivation in 1554. It has soft yellow florets with amber edges, with lavender florets on top of the stalks. Native to dry, sunny, and hot hillsides of Turkey and surrounding regions, this species is less cold hardy (USDA zone 5) than most of its relatives. A related species (macrocarpum) in this group has yellow flowers that turn purple as they age, or in the cultivar ‘Golden Fragrance’ they are yellow with a purple top.
The fourth and most common group of grape hyacinths, often considered the “true” ones, are those grouped under Botryanthus. The namesake species (botryoides) comes originally from Italy, and while once the most common is now seldom seen. You may find a white version of this species, or the cultivar ‘Superstar’ with thick stems and periwinkle-blue florets edged with white. Other species of this group may have dark blackish-blue flowers (neglectum), bright blue with white edges on florets (aucheri) or its cultivar ‘Mount Hood’ (one of my favorites) which is cobalt blue with a white top, or deep violet-blue with a periwinkle-blue top (latifolium). The latter originally came in 1886 from open pine forests in northwest Turkey.
Perhaps the most common grape hyacinth species and its cultivars (armeniacum) are also in this latter group. These have florets that are either sterile, or closed tightly so they can’t be easily pollinated. This means that they often stay in bloom longer. ‘Cantab’ is shorter than the species and flowers later. ‘Cote d’Azur’, introduced in 1987, has a rich lobelia-blue color. ‘Blue Spike’ has double, cobalt-blue flowers. ‘Saffier’ has an unusual coloration– green flowers that mature to a dusky blue from the top down.
Then you may find cultivars not in any one group, likely hybrids of species, including a couple of common ones. ‘Dark Eyes’ has sapphire-blue flowers with white rims, coming from the Caucasus region in 1969. ‘Valerie Finnis’ with its lovely pale blue flowers came from a garden in England, and is named after the plantswoman who found it.
Grape hyacinths are easy to care for, simply needing full sun and a well-drained soil for best growth. They will tolerate part shade, and some soil acidity, but prefer a neutral to slightly alkaline soil. Mix in a small amount of bulb food or just compost when planting, and give some fertility in spring after bloom. As with other bulbs, depth of planting should be about twice their height– about 2 inches deep.
Unlike other bulbs, these begin growth in late summer, with the grass-like leaves remaining through the winter. In cold climates, particularly with insufficient snow cover, these leaves may get injured and look poor in spring but usually recover. Grape hyacinths grow well in USDA zones 4 through 8, often into zone 3 with good snow cover.
Grape hyacinths are most effective planted in masses, although small groups of 3 to 5 may be interplanted among other bulbs or among perennials such as primrose and low creeping phlox, or may be naturalized in open woodlands. If in masses, use natural swaths and curves rather than formal blocks or long rows. They are often used along walks and in rock gardens.
Fruit Tree Diseases
Nov 07
Apple scab, brown rot, and black knot are common fungal diseases on tree fruits in New England. Being ready for these if you have crabapples, flowering cherries, and fruit trees, and knowing cultural controls, will help you have better fruit with the least harm to the environment. A New England website of Extension services (pronewengland.org) provides some photos, information, and further resources on these and other garden problems.
Apple scab disease causes velvety brown lesions on apple and crabapple leaves in spring and summer. It causes corky scars and splitting on fruit in late summer and fall. There are similar scab diseases which attack peaches and pears. Watch for the most apple scab after rainy, cool spring weather.
Since infected leaves drop and produce spores the following spring, which spread the infection, one method of control is to keep such leaves raked in the fall and destroyed. There are fungicides that may be used, but if doing so be sure and follow all label directions. Perhaps the best control if you are considering planting apple trees, or replacing old ones, is to plant varieties resistant to this disease. These, and highly resistant crabapples, can be found in a Cornell University leaflet (plantclinic.cornell.edu/Factsheets).
Brown rot disease kills blossoms of peach, cherry, plum, and other stone fruits in spring. It causes a soft, watery rot on fruits in summer. These infected fruits eventually dry (called “mummies”) and produce spores for the following spring. So one of the best controls is to prune such dried fruits from trees and burn or bury them deeply. Insects create wounds on fruits for the disease to enter, so controlling insects in summer helps to minimize damage. Since most stone fruits are susceptible to brown rot to some degree, fungicides often have to be used for optimum control. Check your local garden store for these, and follow all label directions.
Black knot disease is found on plum and cherry trees. Spring infections lead to an inconspicuous swelling on current year growth during the fall. These swellings turn into green and soft knots the following spring. By the second fall these knots turn hard and black, from a half inch to over a foot long. Since this disease takes so long to develop, it is often overlooked until it is hard to manage.
Prune out branches with such knots during winter, before spring bud break. Make sure to cut the branch at least six inches below where you see the knot, in order to remove all the disease. Remove such knots in any wild plums or cherries that may be nearby as well. Pruning, planting resistant varieties, and not planting trees on sites with the problem (abandoned orchard or infected wild trees adjacent) usually will keep this disease under control without fungicides.
Other diseases to be aware of on apples include cedar-apple rust, fireblight, and powdery mildew. Other diseases on stone fruits include botrytis blight, brown rot, cytospora canker, and powdery mildew. More on all these can be found at the above Cornell factsheet website.
Trees Need Feeding
Oct 11
Have you fed your trees this year? If not, they may be quite hungry, if not starving.
Trees should be fertilized in October, or in April as soon as the frost leaves the ground. By fertilizing in the fall, some of the nutrients will have a chance to be absorbed by the roots and will already be in the ground when the roots resume functioning in the spring.
Since we don’t see the roots, we often don’t realize that they continue growing and absorbing nutrients long after the leaves fall, often into December, and begin work again in the spring before the leaves return. After all, they must be absorbing nutrients and water to enable the leaves to resume growth.
A tree may be getting adequate nutrients from the soil already, but it may benefit from additional fertilizer to keep it growing at its best. A healthy, vigorous tree is much less susceptible to attacks from disease, insects, and other stresses.
The recent ice storm a few years ago shows the difference between healthy and stressed trees. One of the hardest cities hit by this storm, Montreal, lost many street trees to ice damage– trees stressed by many factors including inadequate fertility. Trees in the botanic garden, however, were little affected– trees which had received proper care.
So how do you know if your trees need fertilizer? A tree may need fertilizer if:
1) it makes very little growth, even though it is established and there is adequate rainfall;
2) its leaves in midsummer do not have a good green color, but are yellowish;
3) its leaves gradually become smaller, year after year;
4) its leaves turn to their autumn color and drop in August or early September.
Trees benefit from all of the elements, but usually respond more to applications of nitrogen. Often there is adequate phosphorus in soils from previous fertility.
Trees planted in a lawn will benefit from the same fertilizer as put on the lawn, so if you have fertilized the lawn last spring or early fall, there is probably no need to fertilize trees planted in it. If not, a complete fertilizer (one such as 10-10-10 containing nitrogen-phosphorus-potassium), put on with a fertilizer spreader at 3 or 4 pounds for each 100 square feet, should be adequate. Just make sure you don’t use a lawn fertilizer containing herbicides for broad-leaved plants. Such fertilizer may damage or kill your trees.
For trees not planted in lawns, you may also broadcast fertilizer on the surface. Research has shown this to be effective, reaching tree roots, even in lawns. Or you may choose to root feed.
A common method of root feeding for home gardeners is to buy spikes of tree fertilizer and drive these down into the soil. Another method is to make holes in the soil with a crowbar, or similar tool, and pour fertilizer into these holes. Holes should be about 18 inches deep and 1-1/2 to 2 feet apart. They should start about 6 feet out from the trunk of older and larger trees, and extend out about 6 feet beyond the spread of the branches. For younger trees, make holes about every two to three square feet
For a fertilizer containing 10 percent nitrogen (such as 10-8-6), use 2 pounds for each inch of trunk diameter, measured at waist height. So a tree with a 10-inch diameter should receive 20 pounds of fertilizer.
Another method of root feeding is to use a tube you attach to the hose. On the hose end is a container to add fertilizer tablets. Simply push into the ground, turn on the water, and the fertilizer solution is injected into the root zone. Use similar spacing as above. This is the method usually used by tree care professionals. Such wands can be found in complete garden centers, and specialty garden supply catalogs.
October Gardening Tips
Sep 27
Next spring, don’t be haunted by thoughts of tasks you should have completed in October to ensure a good start to the growing season.
By fall, most gardeners are tiring of garden chores, especially when there isn’t much left to harvest, and thus no really good reason to visit the garden. But garden clean-up is essential both for the health of the soil and an early start on next year’s garden. You’ll be able to get into the garden sooner if you get the plot ready now.
Clean-up involves removing corn stalks, vines, and plant debris, then adding healthy plant materials to the compost pile and discarding the rest. You also should do a final weeding. Why? Because weeds left in the garden will go to seed, producing hundreds of new weeds next year.
Remove stakes, row markers, and other man-made objects. Black plastic and other inorganic mulch materials also need to be taken up as they will not decompose and, if left in place, will provide overwintering sites for some pests.
If you are leaving carrots and other root crops in the ground for winter harvest, be sure to mark the rows. Cover with a thick layer of straw or hay after the first frost to prevent the soil from freezing up.
October is a good time to prepare the soil for spring by adding lime (according to soil test results) and incorporating organic mulches into the soil. The organic matter will begin to break down before next year’s planting and will improve soil texture. You also may want to stockpile well-rotted animal manure in a corner of your garden for use next spring. (Get it now to avoid the spring rush.) Cover the pile with plastic to prevent leaching of nutrients.
Rake and remove leaves from under your rose bushes. This will eliminate a prime “breeding ground” for insect pests and fungal diseases like powdery mildew. Picking up fallen fruit from under fruit trees will keep insects from overwintering and causing problems next spring.
Dig up and store dahlias, cannas, and other summer bulbs, if you have not done so already. Clip off the green growth, then store in a dry, cool location.
Shut down your water garden, moving aquatic plants indoors to ensure their survival. Choose a cool, above freezing, indoor location, placing the pots of aquatic plants in a tub with some water to keep them moist. They don’t need to be as deeply covered as outdoors.
Remove pumps or underwater lights and store in the garage or indoors. If it’s a small water garden, you may want to empty out the water now, so it doesn’t freeze solid. This also is a good time to clean the water garden if needed and repair any small cracks.
Protect your blueberry bushes from winter winds with burlap windbreaks or enclosures. This will minimize desiccation or drying out of foliage, which is detrimental, especially to new plantings.
Mulch with three to five inches of straw to protect plant roots from severe winter temperatures. If straw is hard to obtain at this time of year, use sawdust, pine needles, or wood chips instead. Wait to prune until late winter before new bud swell but after winter injury can be easily determined so you don’t remove new, healthy growth.
Garlic, which requires a cold treatment of 40 degrees F for two months to induce bulbing, should be planted before the end of October. This will give it time to develop roots but not to emerge from the soil.
Garlic needs to be planted in soil with a pH of 6.2 to 7.0. Space cloves four to six inches apart and three to four inches deep. Plant the root side down. Mulch heavily with straw to prevent winter injury.
Other activities for October: wrap trees to protect against winter sunburn or injury from deer and rodents; stock up on birdseed; clean garden tools.
Cannas And Viruses
Sep 11
Cannas are a tender perennial, popular and grown by gardeners for their large attractive leaves and large flower spikes. Being tender, their roots need to be overwintered indoors in cold climates.
Within the last ten years, virus diseases have become widespread in cannas throughout the world, so if you have these perennials you may not want to overwinter them but rather discard them this fall after tops are killed by frost.
If you’re not familiar with the canna, it is the only genus in the Canna family. Although tropical, most of the 100 or more cultivars (cultivated varieties) have been developed as hybrids in temperate climates. There, they are grown outdoors in summer for their bold foliage, coarse visual texture, tropical effect, and flower spikes in colors usually from red to orange to yellow.
Leaves are green, reddish bronze, or striped. Depending on cultivar and conditions they may range from 2 to 6 feet or more tall. They prefer full sun, or at least 6 to 8 hours a day, and warm temperatures. They may tolerate some drought but many also can be grown as aquatic plants. Although tops will die back if frozen, the roots (rhizomes) may survive in the ground if mulched where air temperatures stay above zero degrees (F).
Where temperatures freeze outdoors, plants are cut back after frosted, and then dug, or allowed to dry in their pots, and held overwinter in a non-freezing location. Then water in spring, increasing the amount as growth resumes. This is the process that has been used until recently when at least three viruses have been found overwintering in such plants, and spreading through plants worldwide.
This has resulted in many growers no longer selling cannas, and many collections having been destroyed. Larger and reputable specialty growers, and some botanical gardens such as Longwood in Pennsylvania have obtained or selected virus-free plants and are propagating from these.
Two of the viruses, the bean yellow mosaic and canna yellow streak, are in the potyvirus group which is not passed along in seeds. So plants with these could be grown from seeds and be clean of virus, until reinfected. The canna yellow mottle virus is in the badnavirus group which can be passed through seeds– unusual for viruses– so continues the disease and its spread.
What you’ll see with virus-infected cannas first are short, light green streaks in leaves parallel with the veins. Close inspection shows lots of speckling. These streaks grow larger, then turn to dead (necrotic) streaks, with lighter colored streaks in the flower petals. As more of these dead veins appear, leaves turn a more general yellow (chlorotic) and the plants will be less vigorous.
These symptoms are more easily seen in green than bronze cultivars. It is easy to see in some such as ‘Phaison’ with light green streaks against the red instead of the usual pink striping. In other cultivars, such as ‘Pretoria’, it is difficult to see with the usual yellow streaks appearing more sandy in color. If you’re not sure, watch the leaves as they unfold in spring. If they have such streaks or blemishes they are likely infected.
The only effective solution so far for infected plants is to destroy (not compost) them in trash bags, or to bury or burn them. Destroying infected plants will slow the spread of this disease, and help prevent future “clean” plants from becoming infected. Although you may not see aphids on cannas, these can spread viruses. If a low level of virus, you may not see symptoms or they may be mild and plants may continue to grow normally.
If you suspect a virus infection, and have more than a few plants severely infected, you may want to have a laboratory test done as several other problems such as nutrition may mimic virus symptoms. Check with your local state university diagnostic lab to see if they can do such virus testing (www.npdn.org), or tell you where to send samples.
Underwatering or root stress may result in brown leaves. Spider mites may cause speckling and eventual browning. Blackened leaves, beginning with rust-colored spots on undersides, is likely canna rust disease– most prevalent under hot and humid conditions.
Then, when buying future cannas, make sure the sources indicate if the plants are virus free and discuss how they have ensured this. Even if you buy virus-free plants, they may get infected from sick plants nearby. If you like the appearance of cannas, but avoid or discard them due to virus disease, consider some of the other large-leaved tropical plants as alternatives such as ornamental bananas, elephant ear’s, and ornamental gingers.
