It is frustrating when the leaves start turning yellow and the plant just stops growing for weeks. Sometimes stunted plants recover and are off to the races after stalling for some time, and sometimes they don’t.
How can you tell when stunted plants will recover, but when they won’t?
Stunted growth caused by pests and infections generally cannot be recovered. But plants that are stunted growing under suboptimal conditions have a much higher chance to recover. Such conditions include extreme temperature, excessive light, overwatering or underwatering, nutrient deficiency, pesticide residue, and transplant shock.
It is therefore crucial to identify the root cause of stunted growth in your plants to know whether it has a high chance to recover.
In this article, we’ll go through 8 possible factors and the corresponding remedies to help stunted plants recover.
1. Low or high temperature
Extreme low and high temperatures that are outside of the optimal range for photosynthesis (60 to 104 Fahrenheit or 15 to 40 Celcius) can stunt plant growth.
Low temperatures impair growth because photosynthesis can be halted, causing a hormonal imbalance to push nutrients into the roots, twigs, stems and buds. If it drops below 40 Fahrenheit (5 Celcius) in winter, the cells and structures of non-hardy plants can get damaged.
But many plants such as aloe vera or peaches often go into dormancy during low temperatures and are often mistaken for stunted growth. When they come out of the resting phase, they recover and continue growing.
On the other hand, extreme high temperatures cause vegetables like lettuce or cucumbers to turn bitter and have poor yield quality.
One study suggests an exposure to temperatures above 91 Fahrenheit (33 Celcius) can lead to a reduction in acid content and fruit size for perennial and annual plants.
Solution: For potted plants, move them to a location within their optimal range of temperature. For plants on the ground, try to raise the soil temperature if it is too cold using different methods such as mulching, a cold frame, and a low tunnel. If it is too hot, create some shade above the plants.
The absence of essential macronutrients such as nitrogen (N), potassium (K), phosphorus (P), calcium (Ca), sulfur (S) and magnesium (Mg) often impairs plant growth.
The impact of nutrient deficiency on all kind of plants are basically the same. Depending on whether the deficiency occurs in mobile or immobile nutrients, the symptoms appear on both the old and new growths of a plant.
Nutrient deficiency generally manifests as the yellowing of leaves, also known as “chlorosis”, due to a loss or disruption in the production of chlorophyll, which is crucial in photosynthesis. It can appear on the edges of new and old leaves as well as between the veins with visible green veins like a mosaic pattern.
It can also appear as “necrosis”, or cellular death, causing plant tissues usually at the leaf margins to turn dry, brown, or black. The problem can spread, causing an eventual leaf drop or bud blast.
Deficiency in potassium can result in weak stalks and burnt leaf tips. If the underside or upper sides of the leaves are turning purple, your plants could be lacking phosphorus which promotes photosynthesis.
Deficiency in Calcium causes “dieback” or burnt tips on new leaves since Calcium helps with plant cell formation. While an early sign is the dropping of flowers, the leaf tips will eventually burn, and the fruits will look smaller than usual.
When plants are deficient in magnesium, they’ll experience stunted growth due to low chlorophyll production. The leaves show signs of magnesium deficiency by turning pale while the veins remain green.
There will also be signs of stunted growth when essential micronutrients are inadequate. The common micronutrients include zinc, boron, manganese, iron, copper, chlorine, and molybdenum.
Solution: Feed your plants a low dose of NPK fertilizer frequently, especially Cal-Mag in later winter or spring for new growths.
Different plant types have different tolerance to light, which is crucial for photosynthesis, a process for plants to generate carbohydrates.
Plants like Phalaenopsis orchids, Dracaena, Peace Lily, and the zz plant make great indoor plants because they can only tolerate low light conditions and will exhibit symptoms of stunted growth under high light conditions.
A common symptom of high light intensity is their leaves turning pale or discolored.
Low light conditions, however, would only lead to etiolated or elongated stems but do not stunt plant growth.
Solution: The sunburnt areas can be left alone without removal. To recover, move the potted plant to a cooler location or provide shade to the grounds in the garden.
Pests and pathogens can also stunt plant growth because they often attack the leaves, thus inhibiting photosynthesis.
Infections caused by bacteria or fungi (e.g. downy mildew, fusarium wilt, and clubroot) often cause rotting and yellowing of the leaves and distort the rate of cellular growth.
Most insects or pests also prefer to feed on the leaves, stems, and buds of younger plants. That would affect their process of photosynthesis and thus the production of food necessary for optimal growth.
Unfortunately, plants that are stunted by pests and pathogens often cannot recover because the infection can spread quickly to other areas and the problem is often too advanced when it is discovered.
Solution: The infected area must be removed immediately by using sterilized cutters before it spreads to other areas. Use fungicide such as Physan 20 or 3% hydrogen peroxide solution to kill fungi, bacteria or pathogens. Keep the infected area dry by dusting over some cinnamon powder which serves as a natural fungicide. Remove it from other plants to prevent any pathogens from spreading.
The problem of soil pH is related to nutrient deficiency.
Most plant nutrients are readily available for absorption in a low pH or acidic environment. In particular, Maganese (Mn) and Iron (Fe), which are minerals crucial for chlorophyll production and photosynthesis, are best taken up by the roots when the soil pH is low.
Although most plants do not require a high amount of such nutrients, acid-loving plants require higher amounts of such minerals and are thus most sensitive to the soil pH.
Dehydration or a lack of water causes leaves and the tender parts of the plant to shrivel and wilt, while excessive water in the growing medium can cause root rot and leaves to turn yellow.
When the roots absorb too much water, the pressure inside the plant builds up and causes cell walls to rupture. This makes the leaves turn yellow.
Humid conditions also create a suitable environment for harboring mold and pests like gnats, which make the plant become vulnerable to infections.
That is why it is crucial to choose a growing medium that retains the amount of water appropriate to the plant’s water needs.
For example, succulents, cacti, and orchids do not like to be in a waterlogged growing medium. They, therefore, grow best in a substrate that does not retain water and has good drainage. Examples include chunky materials such as gravel, perlite, coarse sand, lava rock, and bark chips, instead of potting soil or compost which are highly water retentive.
Prolonged dehydration however can significantly lower the recovery rate of stunted plants. Stunted plants begin to wilt entirely once the dehydrated cells in the leaves and stems have collapsed.
Solution: Change the growing medium to one with better drainage. Change the watering habits, which can be less frequent and/or bottom watering instead of watering from above.
7. Pesticide residue
Pesticides are made of synthetic compounds that could kill beneficial microorganisms which are crucial for maintaining soil fertility and the healthy development of plants.
If the toxicity levels are high, stunted growth would be an adverse effect a grower might have to deal with.
Solution: The only way to solve the problem of pesticide residue is to prevent growing in soil with pesticides. Be aware of the safety of the soil or compost purchased from an external source.
8. Transplant shock
Transplant shock happens when there is a drastic change in growing environments and can definitely put a setback to plant growth. This happens especially to young seedlings with delicate roots which are often damaged during the transplant. If the damage of roots is not serious, they usually recover after 1-2 weeks in the new environment.
Solution: Germinate your seeds in heavy-duty seed starting trays with a large drainage hole on the bottom that you can push your finger up to pop out the seedlings without hurting their root ball.
How long do stunted plants take to recover?
In most instances, stunted plants regain their vigor after removing the stress factors.
The time it takes for stunted plants to recover varies depending on whether you are dealing with nutrient deficiencies, pests, diseases or poor growing conditions.
If the stems are still alive, new leaves can sprout in 3-4 weeks, or less.
Plants that are stunted due to viral or fungal infections have a low chance to recover because the infection often spread quickly and it is often too late when the problem is discovered.
But plants that are stunted growing under suboptimal conditions for a short period of time have a much higher chance to recover. Such conditions mentioned above include extreme temperature, excessive light, overwatering or underwatering, nutrient deficiency, and pesticide residue.
Many growers might have to deal with stunted growth at some point. There are different factors that lead to stunted growth.
With the right remedies and suitable growing conditions, it will be easy to make your plants recover. Trimming the dead stems and leaves can give room for new growth.
You also want to moisten the soil only when it feels dry to avoid the harmful effects of overwatering. Most of all, your plants need a consistent supply of essential nutrients.
Johnson, G. & Ernest, E. G. (2018). Stunted Vegetable Transplants. University of Delaware: Weekly Crop Update
Oregon State University extension service. Environmental factors affecting plant growth
Hatfield, J. L & Prueger, J. L. (2015). Temperature extremes: Effect on plant growth and development. Science Direct: USDA Research and Programs on Extreme Events
Jiang, Q. Y. (2020). Identifying Nutrient Deficiency in Plants. National Parks Buzz
University of Missouri (2011). Diagnosing Nutrient Deficiencies. Integrated Pest Management
Hentchsel, R. (2020) Chilling Hours Help Break Spring Dormancy. University of Illinois Urbana.