Last Updated on May 12, 2023 by Griselda M.
May Night Salvia is a tough beautiful plant. Problems with salvias, especially issues with flowering are relatively easy to fix if you understand how. This rugged, deer-resistant, stunning flowering plant is a beautiful addition to the edges of your garden. Read on to discover 12 common problems with May Night Salvias and how to fix them.
What Are Salvias?
Salvias are a genus of plants in the sage family that is distributed throughout much of Europe, Asia, Africa, and the Americas. My favorite species is Salvia africana which is a wild bee magnet. In the horticultural world, Salvias normally refers to a group of plants of a much smaller range that are grown for their flowers and beautiful foliage.
One of the more popular of these is the May Night Salvia or Mainacht Salvia which is a hybrid that produces beautiful violet-blue spikes of flowers. This article deals with the May Night Salvia and common problems with salvias of this cultivar and similar ones.
You will read a lot of guides that suggest quite delicate treatment of May Night Salvias – the first time I grew these was by mistake when the local garden service dropped off trimmings in the leaf litter I use for mulch. I believe in mulching everything and some of my mulch started to grow and I identified the flowering plant that came up as May Night Slavia. It is remarkably easy to grow if you give it the right conditions.
Nurseries sell these as rooted cuttings or seedlings – you can buy them in seed trays or bags. Both are effective and are nearly impossible to kill as long as you water them once or twice a week or so once established and do not overwater them. I try to plant salvias in a rich soil comprised of compost, sand, and 20% pearlite (I use my old potato soil mix). A little bit of manure as mulch each year helps keep them healthy. This plant is however able to grow, albeit a bit more poorly, in clay soils as well.
The best time to plant a May Night Salvia is just after the last frosts in Spring. Once they are established they can tolerate pretty harsh weather (Zones 4-8), but early-stage transplants are more sensitive so get them in after the last frost and let the plants establish over summer before they need to learn how to deal with winter.
Damping-off of seedlings and transplants
As a side note, be careful not to overwater seedling transplants. These can, in the earlier months of the year, damp off. When the stems are still green-gray and soft the plants are partially susceptible to various fungi that can kill the roots and stem causing them to damp off. Water once every two to three days, or as needed to keep the soil just damp but not wet. When the plants are young, their ability to absorb a lot of water is quite low and they can end up drowning if you overwater them.
12 Common Problems With May Night Salvias
1) Wilted leaves – Overwatering
The ancestral genetics of the May Night Salvia comes from plants that grew in the northern, forested bits of Europe and Asia. These plants thrived in damp, forest-type top soil with the sandy aged soils typical of this region providing good drainage.
If you overwater compost-rich soil, the soil will actually begin to rot and this uses up oxygen, causing the roots – which need some oxygen – to become stressed and die. This means that the plant will look wilted and dry, but the reason for this is that it has lost its roots and that is why it is dry.
These sorts of stick and measure meters are quite useful while you are learning. I would keep the soil somewhere between normal and wet on this meter. Wet is not good unless you have just watered the plants. Let the soil go to being nearly dry, and water again. Salvias are actually quite tough and can tolerate a bit of dryness – this forces them to put their roots deeper into the soil, and this, in turn, makes your plants much healthier and more hardy. If the soil is very wet all the time their roots scoot along the surface where there is a little bit of air.
2) Wilted leaves – Underwatering
I have found that my Salvias are really really tough. I have quite a heavy mulch that I put around them. The mulch as you may remember is actually why I have them in the first place! The mulch produces an ever-developing compost layer and also keeps moisture in the soil/compost mix. If you do however have a patch of dry weather and do not water them, you will be able to check the soil, and if it feels/measures as dry, and the plants are wilted, you can water them.
Generally, they bounce back really fast with a good watering – sometimes, there may be some damage to the leaves and you can just cut any dead leaves and stems off. The plant shoots up from the base and will recover with time.
3) Yellow salvias – Watering issues
Salvias are tough plants that generally tolerate quite a bit of abuse. However, overwatering as mentioned above, causes the roots to be damaged, and after this, it will cause older and gradually younger leaves to die as the plant essentially rots from the root up.
If you underwater a plant for too long, it will begin to go dormant to save itself, and in this case, the entire plant goes yellow.
4) Yellow salvias – Nutritional issues
Several mineral deficiencies can cause the yellowing of the leaves of Salvias. I have had a few nutrient issues in my soil and about two years ago, I managed to irrigate my garden more than I should have and wash the potassium out of the upper layer of the soil.
In this case, you will notice that the older leaves go yellow and brown on the outside and then the middle of the leaves stay green.
These plants are generally quite tough, and it is difficult to give them major nutrient deficiencies if you keep feeding them compost and mulch. They can however under certain conditions develop Nitrogen deficiency. This will cause an overall yellowing of the plant and it takes on a pale pathetic look.
There is a temptation to run out and buy a chemical fertilizer – Salvias are not big feeders and the risk of giving too much nitrogen is quite high with a chemical 2:3:2 or similar fertilizer. I would suggest using an organic slow-release multi-nutrient fertilizer.
The above, and similar organic fertilizers, together with the addition of compost and weathered manure (small amounts) will keep your soil around the salvias vibrant and healthy. This plant’s natural function is to grow on the edge of forests and trap leaves and feed off these as they break down. Mimic this environment and it will thrive.
5) Salvia not blooming / Salvia not flowering
In my area, there are quite a few trees that provide excess shade, and in the areas where there is insufficient light, my Salvias do not flower. This is not really a problem for me as I just like the color of their leaves.
In sunny spots, where you get abundant sunlight, they will tend to flower if they get enough sunlight – about 6-8 hours a day. This can be in a spot where they get sunlight in the morning for a few hours, then midday shade and late afternoon sunlight for a few more hours to give 6-8 hours a day of direct sunlight. This mimics what would be expected on the edge of a forest in its natural environment at higher latitudes.
If your salvia has a good layer of compost and mulch, and you have given it a slow-release organic fertilizer such as the one listed above, it will not have nutrient deficiencies and the soil moisture should be ok. In this case, the only real cause of it not flowering is a lack of sunlight.
6) Plant goes gray and the leaves die
If this happens on the top of the plant, it is probably powdery mildew, and on the bottom, it is Botrytis blight. I normally find that powdery mildew and botrytis blight is one of the secondary symptoms of whitefly infestation and poor airflow. Look under the leaves and see if there are little white insects that flutter away when you disturb them. Whiteflies transmit powdery mildew and are a general pain in the neck.
If the underside of the leaves are fluffy and white it is Botrytis blight – another irritating fungus.
I spray my plants with Neem oil. Neem oil inhibits the enzyme the whitefly use to escape their skin when they molt causing them to basically die in their skin. Neem oil is also, rather usefully, toxic to powdery mildew and botrytis – hence you manage to kill three birds with one stone.
I spray neem oil once every three days for serious infestations, or once every two weeks prophylactically. The Prophylactic spraying is preventative – hence you are spraying only when you think there is a risk. I spray in misty wet warm periods – this is when powdery mildew, whitefly, and other pests thrive. Botrytis is also controlled by prophylactic spraying. I find that botrytis is a pretty rare occurrence. If you find it is a problem, plant your salvias in a place with better sunlight and better airflow.
7) Leaves go spotty yellow
This is a symptom of spider mites. Look on the underside of the leaves and look for little red dots and spider web-like material. These tend to be a problem in hot dry weather. Much like for whitefly, neem oil spray is perfect. Treatment for red spider mites is really just symptomatic – if you see them starting to be a problem, kill them with neem.
8) Long scraggly plants that fall over
I have had Salvia become quite scraggly and threadbare looking. They can get long and stretched out, looking leggy and pathetic and then they collapse on themselves and rot and generally make a mess. This is normally due to reduced sunlight – which causes them to stretch towards the sun. You may find that a tree has grown a bit somewhere in the line the sun tracks across and a perfect bed has now got a bit shaded. The plants try to grow up towards the light, and then collapse.
I have several Fiskars products that I use in my garden, including my beloved Fiskars 27″ Maul which keeps my house provided with firewood. The Fiskars pole saw is a lovely piece of engineering.
You can look back from the flower bed and look for branches that cast shadows over your flower beds, and then using the pole saw you can trim these branches off. I have had several different products, including a Stihl Pole Saw (I love my Stihl chainsaw, but their pole saw is useless) and I can firmly say the Fiskars pole saw is probably the best design I know of. It has a fiberglass handle – many pole saws have metal handles meaning you will fry yourself if you accidentally drop a branch on a power line (this happens easily).
Buy a spare blade when you buy the saw and keep that handy. The blades last about two years maintaining a three-acre garden like mine. If you use them in the rain, they get dull faster – it helps to spray the blade with WD-40 before and after cutting.
I find oak trees have acidic sap and this kills the blade fast – spraying with WD-40 really helps. If you are cutting trees that have a lot of resin (pines, cedar, etc) it helps to spray the blade every few branches, and this seems to stop the blade from getting gunked up with resin and sawdust (really irritating).
Pruning tall trees is great fun – unless you know your way around cutting trees, do not try to cut branches over about 4″ in thickness – and always wear a helmet. When big branches hit you on the head you can develop multiple personality disorders quickly (splattered brains all over the place).
9) Funny-shaped leaves – Aphids
Sometimes you will find a few deformed leaves – when you look under these you find a clump of little insects nesting in the deformed bit. These are normally aphids. I just remove such leaves and feed them to my chickens – chickens love aphids. Neem oil controls aphids. Be sure to wet under the leaves.
10) Plants get covered in caterpillars after they flower
Caterpillars are the larval stages of butterflies and moths that are attracted to the flowers and lay eggs that develop into caterpillars. If this happens, live with it! Butterfly species are in monumental decline – think of it – when last did you even see a butterfly? When I was a kid you drove 10 miles in summer and had to clean the radiator to stop your engine from overheating! Now you can drive across the country and get one splat on the window if you are lucky.
I cherish every butterfly I see these days – I hope my kids and grandkids will enjoy being able to chase after beautiful bright wings flapping through the grass as I did. If we do not live with nature, we will most likely cease to live.
11) Big round holes in leaves – Leafcutter bees
I often find my Salvia leaves to get more and more holes towards winter as the population of leafcutter bees increases. Here is an article I wrote on these bees. If you get holes cut in your leaves by these bees consider it an honor and explain to everyone that this is why it looks like somebody took a shotgun to your salvias – you are conserving wild indigenous pollinators.
You can even follow my advice in that article and put up a nesting site for these beautiful largely harmless bees (If you take one and stick it on your tongue it may sting you – as a now prominent aphidologist in Nevada once discovered in the Congo).
Leafcutter bees are some of the best, most faithful pollinators you can have. To explain – a honeybee can fly miles to flowers – if it finds something better than your strawberry plants, or your blueberries, it will just go there – they are not faithful.
A leaf-cutter bee loyally pollinates flowers within a few hundred feet of where she nests. If she is cutting holes in leaves in your garden to make a nest for her babies, she lives in your garden and she faithfully pollinates every flower you have! Live with her and love her for the magical little creature she is.
12) Lots of dead flower stalks
After flowering and pollination of the May Night Salvia, the flower develops into a dry woody mess that can produce seeds. These are best dead-headed – cut off – before the plant decides it does not want to flower anymore. Many perennial plants will keep flowering until they set seed. If you keep removing the flower heads this encourages the plant to keep producing more flowers until it gets something to set seed. In nature, animals love eating flowers, so this is how plants have adapted to herbivory pressure.
In Summary: Most Common Problems With Salvia Plants
In this article, we have seen that problems for salvias include the damping-off of seedlings, stem and root rots, powdery mildew, Botrytis blight, aphids, spider mites, and whiteflies. In short, if you put the plants in an area that gets enough sunlight, exposure to air movement, and has well-drained soil, you should have few problems.
Use only organic slow-release fertilizer, mulch, and well-weathered manure on your May Night Salvias and you will be rewarded with beautiful, butterfly and bee-attracting flowers that just make your garden special. Enjoy!
Dr. Garth A. Cambray is a Canadian/South African entrepreneur and beekeeper with 28 years of experience in apiculture and specializes in adding value to honey. His Ph.D. research developed a new advanced continuous fermentation method for making mead that has resulted in a number of companies globally being able to access markets for mead. His company, Makana Meadery, exports honey mead to the USA where it is available to discerning connoisseurs. He has also developed technologies to commercially manufacture organic honey vinegar in Zambia for export globally. He holds a few patents globally in the ethanol industry and believes in technology and knowledge transfer for human development and environmental sustainability. One of his proudest achievements is the fact that the wind farm he started at one of his old apiary sites has essentially made his hometown carbon neutral.