Gardening is both an art and a science, but often there are factors outside our control that cause plants to die. So, if you’re new to the game and find yourself staring into the abyss asking ‘why do plants die?’, then we’ve got the perfect beginner’s guide to gardening below.
Read on to find out how to avoid the most common plant problems, and maybe get some reassurance from the fact that some plants are simply short-lived!
Why do plants die?
In this tutorial, we’ll be running through some basic problems, like plant-killing diseases, and some simple mistakes you can avoid to achieve a healthier garden and keep plants alive.
We’ll start with diseases, growing problems, and pests, but then look deeper into the science and biology of plants so you can choose long-lived plants, and avoid those that need more regular care (if you’re after a low-maintenance garden that is).
Common reasons that plants die
The three most common reasons plants die, other than age, are:
And in every single case, prevention is far better than cure!
To keep things simple, we’ve compiled three tables, each with details of common problems, their symptoms, and how to fix or, better yet, how to prevent them in the first place.
Plant killing diseases
|Blight||Black or brown patches along a stem, or brown circles on leaves, with yellow rings.||Remove any blighted material and burn it.|
|Canker||Dark pits in the bark of trees and woody shrubs. Advanced cases will have orange pits in the leaves.||Remove any affected material and burn it.|
|Root rot||Wilting leaves that look dry, while the soil is wet. Black, brown, or mushy roots.||Lift the plant, and cut out any bad roots. Rinse the remaining roots, and plant it into fresh compost.|
|Club root||Club root stunts plant growth, and causes yellow leaves, particularly in brassicas (cabbages, broccoli, etc.).||Club root is a fungal infection that needs brassicas to survive. Remove the plants, and do not plant in the same spot for at least three years.|
|Xylella||Leaf scorching that looks like sunburn, and generally wilted growth. Shriveled fruit, and premature leaf loss.||Cut back affected material and burn it. The bacterial disease is spread by insects, particularly moths and spittlebugs, so remove them when you see them.|
Plant care problems & growing conditions
|Over-watering||Dry leaves, or yellowing wilted foliage.||Reduce watering until the soil has dried out. Roots may begin to rot but can recover in most plants.|
|Sunburn||Brown leaf tips. Pale, crisp foliage.||Move the plant into the shade, or if that’s not possible, make sure it is well watered through any droughts to counteract the heat.|
|Nutrient deficiency||Yellow leaves, or leaf tips. Stunted growth.||Test your soil and add the appropriate fertilizer or mulch.|
|Aphids||Clusters of white, black, or green insects along new growing tips.||Scrape the aphids off, or introduce predators like ladybugs.|
|Slugs||Slime trails and large bites out of fruit or leaves.||Go out at night with a torch, and pick them off your plants, or install chemical-free slug traps.|
|Ants||Rapidly defoliated plants, usually perennials.||Encourage birds into the garden, or pour hot water into their burrow.|
|Moths & Caterpillars||Wrinkled or puckered leaves, with bites taken out.||Remove the caterpillars and put them on a bird table. Birds will learn that they’re there and eat the rest (usually).|
|Spider mite||Small yellow or orange spots on the surface of the leaf, with corresponding brown marks on the underside.||Water plants slightly more. and increase ventilation. Spider mites like dry soil.|
Plants with short life spans
Once you’ve resolved any of the above, it’s worth bearing in mind that there are a few different groups of plants that will die after one year, or just a few short years, in your garden. This isn’t a problem, just an opportunity to fill their space.
- Short-lived perennials
- Tender perennials
Annuals (most vegetables)
Annuals, a group of plants that includes most vegetable groups (cucumbers, squashes, salads, beetroot, celery, etc.) are plants that go through their entire life cycle in one year. They start the year in spring, or in late fall before spending winter largely dormant.
Annuals then develop leaves and foliage through spring and early summer, before flowering towards the end of the growing season. Finally, annual plants produce seeds, which can be harvested, or left to fall to the soil to replace their parents.
So if your prized flowers and vegetables are turning brown, wilting, or completely dying back, don’t worry, this is normal!
Another plant group containing many vegetable species is short-lived perennials. But this group also contains many ornamental garden plants, like perpetual sweet peas, or penstemon, which will thrive for a few years, and then fade. In most gardens, tomatoes and peppers won’t over-winter at all, so are treated as annuals, but are technically short-lived perennials.
Again, when short-lived perennials begin to fade after a couple of years they have simply exhausted themselves, and are ready to be replaced. Early signs of aging are reduced flower production (usually year three or four), and a higher prevalence of pest damage as plant defenses are dropped.
Tender perennials group together many different plant groups, and have a distinctly blurred boundary with short-lived annuals. Tomatoes and peppers fall into both categories, while bananas and even some shrubby fruit bushes like pomegranate and citrus are not particularly winter-hardy either.
If you don’t have a greenhouse, tender perennials are hard to keep alive and will blacken over winter if subjected to frost. They tend to be tropical plants, or sub-tropical plants that like high summer heat, and mild winters.
If you identify these plants in late fall before frosts, you can dig them up and move them indoors, or into the greenhouse. Failing that, try wrapping them in fleece. They are mostly dormant over winter, so won’t mind having their light blocked out, and will stay cozy and warm until spring, when you unwrap them, ready to sprout after the last frost.
Biennials are possibly the most confusing plant group there is, with many doing their work in their second year, while others are actually far more useful in their first.
Take onions for example. Onions are biennial flowers, with gorgeous globes of flowers in their second year, but actually need to be harvested in their first year while the goodness is stored in their swollen bulbs. Garlic and leeks are the same.
Brassicas are also technically biennials, best sown in fall to over winter, which gives them better flavor in spring. Some, like broccoli, are only harvestable in their second year, as the crop is the flower. Others, like kale, are better in their first year as they bolt and set flowers and seeds in their second, making the leaves tough and flavorless.
After flowering, biennials can continue for a few years before fading, but will usually fade.
Can you save dying plants?
If your garden is still struggling, and you’ve got a plentiful array of green, hardy perennial plants that are looking sad or faded. Or, if your annuals are dying too early in the season, way before they should crop, there are plenty of ways to save dying plants.
How to save plants from common diseases
Trees and shrubs have a slightly different set of problems to herbaceous plants (loose definition: green-stemmed plants). As such, the guide below should be taken as general, rather than specific to any one plant, but both fungal and bacterial infections can occur in all types.
The most common fungal problem for cooler climates is mildew, caused by cool humidity, and moved by wind. In warmer areas, blight is more common, but can happen regardless of temperature. Both create moldy surfaces over the leaves and stems of plants, but blight is brown and black, with visible spores when touched. Mildew is typically white. Both should be treated by removing any damaged material and burning it to prevent re-infection.
Other common fungal problems include verticillium wilt (v-shaped marks on the edge of leaves), rust (orange pustules, which eventually meet up to create orange foliage on otherwise green plants, and root rot.
Nearly all fungal infections are spread by insects, wind, or dirty tools, and take hold wherever a plant is wounded, either by insects, or tools. However, root rot and blight (particularly southern blight) can affect annual plants very badly as a result of overwatering, which increases humidity, and causes stagnant water which promotes fungal growth – particularly in warm conditions.
Bacterial problems can look the same as fungal ones, and the effects and treatment are similar. However, while you can treat fungal problems with fungicides and desiccants (bicarbonate of soda, vinegar, etc.), bacterial problems simply need to be cut out and disposed of.
One of the most frustrating bacterial disease that kills plants is canker. The are many types of canker, but the worst one in edible gardens is fruit tree canker, which creates sunken pits in the bark of trees and shrubs, usually darker than the usual bark color. If left untreated it will spread both up, and down the trunk, spoiling fruits, and ultimately killing the tree, before moving to other woody trees in the garden.
If you see canker, it must be removed at least 1ft below the damaged area, which can often mean removing a large portion of your tree. This does not mean your plant is dead! Most trees will recover once canker is removed, and after two or three years, will likely produce higher yields as a result of a harsh prune.
How to stop plants from dying
Under-watering is unlikely to kill most plants, so forgetting to water for a week, often even a month, will not kill a plant, but will affect its health. Overwatering kills far more plants than underwatering by promoting the fungal problems we discussed earlier.
Gardening is generally pretty intuitive, but when it comes to finding the right location for your plants, it can be surprisingly tough. For example, tropical plants don’t necessarily need full sun. Many are forest-floor tropicals, meaning they thrive in dappled shade. Research every plant to find the right location.
Too much sun can cause sunburn, while too little can kill plants entirely as most plants need sunlight to photosynthesize (making the sugars they need to survive).
Soil / Nutrients
Any plant you buy will have some basic information on the label about the type of soil you can plant in, but for fresh-faced gardeners, the terminology can be confusing.
It’s worth investing in a basic soil testing kit for any new garden, so you can get an idea of the sort of nutrients that are available in your existing soil. Then, use fertilizers and mulches to improve drainage, moisture retention, or nutrient levels accordingly.
|Clay soil||Clay soil is the most complained about soil by gardeners, but it is really quite misunderstood. Clay soil has poor drainage, and heavy water retention, which makes it unsuitable for many tropical species. However, it is packed with nutrients, and will only dry out completely in severe drought.|
|Sandy soil||Sandy soil is not an indication of nutrient levels, but rather a sign of very good drainage. Depending on where you are in the country, sandy soil can be rich in minerals but will need improving with either soil improver or compost to boost moisture retention. Otherwise, water will run through too quickly for most plants, meaning those minerals go unused.|
|Loam||Loam is the ideal soil for any garden. It is a mix of sand, silt, and clay, and is particularly prevalent on old alluvial sites, where different geologies mixed. |
Loam has the drainage qualities of sand, with the nutritional benefits of clay. And can be easily created in most gardens over a few years or by mulching poor soils with good compost.
|Compost||Compost is decomposed plant material and organic matter. It can be made at home from kitchen scraps, grass clippings, and leaf litter, and after two to three years is a brilliant planting medium for vegetables thanks to high moisture retention and balanced nutrients.|
|Humus||Humus, or humus-rich, soil is effectively soil with a fine, moisture retentive structure. After three or four years, compost will become humus. Its nutrient levels are lower by this point, but it makes a great planting medium and an ideal seed starter.|
If you’ve done everything else right, but are still suffering from plant infections, there could yet be one final cause; hygiene. Not yours, of course, but that of your tools. Dirty, rusty, or blunt garden tools hold onto fungal spores and harbor bacteria. To avoid spreading diseases between plants clean your tools regularly. That goes for tomatoes as well as hedges and shrubs. At the very least, rinse your secateurs after each plant.
If you get all of that right, your plants will live long, healthy lives. Fungal problems will always occur in domestic gardens, as they spread from neighbor’s yards, and live for several years in the soil, but regular and attentive care goes a long way in keeping plants alive.
So, that question you were asking earlier; ‘why do plants die?’. Hopefully, you’ve got your answers. And remember, we’re always here at Tiny Garden Habit, with new advice for gardeners, no matter how dedicated, from newcomers to seasoned pros.