Winter gardening woes and how to solve them

by | Jun 24, 2021

Winter gardening woes and how to solve them

We are now at the beginning of our winter months and with the season change, we as gardeners face new challenges in our garden – from the weather itself to the pests and fungi that become prevalent in the winter months. We’re sharing some tips to help solve some of these problems. Remember, garden problems cannot always be solved and some fatalities in the garden are fairly normal. So don’t be too hard on yourself!

This blog will cover:

  • Winter rainfall problems
  • Frost-prone area problems
  • Winter pests – Aphids
  • Winter pests – Caterpillars
  • Winter pests – Cutworms
  • Winter pests – Scale
  • Winter pests – Snails & slugs
  • Winter fungi – Black spot
  • Winter fungi – Downy mildew
  • Winter fungi – Damping-off disease
  • Winter fungi – Powdery mildew
  • Winter fungi – Rust

Problems in winter-rainfall areas

Most of South Africa experiences summer rainfall but a small part, being the south-west and the Western Cape area, experience winter rainfall and therefore have a different climate and unique winter gardening problems.

  • If your garden has a heavy clay content in a winter rainfall area, you may experience drainage problems and therefore experience rotting of plants, etc. It is said that this can be remedied over time with the addition of agricultural lime to clay soils, which helps to break this type of soil up. What most don’t realise is that agricultural lime has also got the potential to alter the PH of your soil, which can be harmful (Fynbos, for example, cannot handle alkaline products). Gypsum is another product that is used for breaking up clay soils but there are varying opinions as to whether Gypsum is actually an effective product for this purpose. Our recommendation is to rather apply and work large amounts of organic matter like compost and well-rotted manure into heavy clay soils as this will over time improve the structure of the soil as well as to help with drainage. When the organic matter breaks down it will also feed the plants. 
  • Another problem in winter rainfall areas is that, when heavy rains occur, some young plants often get washed away. You can prevent this with mulching around the younglings and in general.
  • Plants that come from more naturally arid areas can experience rotting when there are consistent heavy rains. Examples of these are succulents, cacti and aloes. If plants are in pots it is a fairly easy problem to prevent or remedy – by using gravel or grit as a mulch around the plants as a collar (Prevent stem from being constantly wet). Also apply this method in garden beds. 
  • When mulching, be careful to not apply too thick a layer and make sure that the mulch is not piled high around plants or tree trunks. This is because mulch can hold moisture, which in turn can cause rotting and lead to fungal growth when there is lots of rain. Once plants start rotting, there is not much you can do to remedy the organic decomposition process, so do a spot check on your mulching level during the rainy season to make sure it is not piled up too high.

Problems in frost-prone areas

Some South African summer rainfall areas experience extremely cold winters and frost. There are a few things you can do to minimise frost damage to your plants. 

  • When plants are damaged by frost, do not cut back frost damage as these parts can protect the plant from further harm. Cut it back once all cold weather has passed. 
  • If you see that certain shrubs or small trees are suffering quite heavily from frost damage, rather transplant these into more protected and appropriate areas. This is the correct time to transplant trees and shrubs that may have originally been planted in inappropriate areas as plants are fairly dormant in winter. When transplanting, make sure you water the plant well the day before and try to limit damage to the root ball of the plant which you are transplanting. 
  • If you know you have susceptible plants in your garden that don’t naturally cope with frosty conditions, protect them with some form of frost cover to minimise damage. Examples of frost cover are grass wigwams, frost fleece and hessian. 
  • A lesser-known fact is that frost-prone gardens must get adequate watering. This is because frozen soils do not yield water. Make sure, though, that this watering takes place in the morning. Morning watering is important, so that plants and roots can dry out through the day and do not stay wet at night.  
  • In frost-prone areas the freezing and thawing of soils takes place naturally and this churning and heaving can be damaging to the roots of plants. Adding mulch to the garden regulates the soil temperature as well as moisture, which eases the transition into winter. Mulching creates a buffer against hard weather.

Winter Pests : Aphids

These small, pear-shaped, soft-bodied insects come in various colours and like to suck on plant sap from a broad spectrum of plants throughout the year. They are preferential to new and young plants. This activity sucks the energy out from plants, weakening growth. Aphids can also carry viruses that can be deadly to plants. 

  • When you have an aphid infestation you may notice ants running up and down the infected plant. This is because they have a symbiotic relationship with aphids. The aphids secrete honeydew which the ants eat and in return the ants protect the aphids from natural predators. Unfortunately, your plant is the host to this alliance.
  • At this time of the year, one particular type of aphid is very active and also very destructive, causing the complete dying-back and browning of whole branches. The cypress aphid, as the name says, attacks cypress and conifer plants. If left unattended it can be fatal to your plant or tree. Treat the cypress aphid with a systemic insecticide like Insecticide Granules, which is very efficient.


Make a homemade spray by mixing 3 tsp of cornstarch with 1 tbsp of cold water. Bring 250ml of water to a boil and then mix the cornstarch mix into the boiled water. Boil and let this mix thicken. To use this, mix 125ml of the premix with 5 litres of cold water and spray it onto the affected plants.

Winter Pests : Caterpillars

At this time of the year, we plant a lot of winter-flowering seedlings and winter-bearing vegetables. Many of these veggies are in the brassica family – which is particularly susceptible to deadly attacks by caterpillars. There are many different types of these Larvae that can attack your garden. 

Please, however, take into account that caterpillars are young moths and butterflies, which are all pollinators. If you have decided that you need to treat the plants affected, then opt for a shop-bought product like Margaret Roberts biological caterpillar insecticide.


Make a  homemade spray by crushing 4 hot chillies, 1 small onion, and 1 clove of garlic, and adding this to 2L of water. Bring the mixture to a boil and then let the mix steep for 2 days, after which you can strain it and spray it onto the affected plants. This spray is also effective for aphids and other soft-bodied insects.

Winter Pests : Cutworms

The cutworm caterpillar, which is the early beginnings of a moth, varies in colour but is a smooth and hairless worm that curls up tightly when disturbed. 

  • Cutworms can be problematic at this time of the year – when we plant our winter annuals and veggie seedlings & seed (Target young plants). 
  • The mature cutworm larvae are very destructive, cutting straight through young plant stems, immediately killing the plant. 
  • A great solution is to recycle toilet rolls and use them as plant collars when planting. 
  • You can also sprinkle cornmeal or bran around the affected areas, which they will eat and die from. 
  • Cutworm can also be controlled by putting matchsticks on either side of the newly planted seedling, flush with the seedling. When the cutworm tries to curl around the seedling the matches will get in the way.

The above product which contains Bacillus thurengiensis, Margaret Roberts biological caterpillar insecticide is also effective. Bacillus thurengiensis is a bacteria which when eaten by caterpillars and worms produces proteins that paralyze the caterpillar’s digestive system, which causes them to stop feeding and die. It is safe for use in organic gardens because it has a specific target and is nontoxic to humans, animals, and beneficial insects.

Winter Pests : Scale

Soft and hard scales exist in many different colours and types. Scale can be present throughout the year. It likes to overwinter on larger shrubs, trees and fruit trees and this is where you are likely to find them hiding. 

  • Scale like aphids, are sap-sucking insects that secrete honeydew and have the same symbiotic relationship with ants. Something not mentioned before is that, on top of the honeydew, black sooty mould is likely to form. This is a telltale sign of a serious problem. 
  • If you would like to purchase a product, you can opt for Oleum – an environmentally friendly oil insecticide that works by suffocating insects and eggs.


A homemade solution is to mix 30ml (1 tbsp) of methylated spirits or surgical alcohol and with 250ml (1 cup) of water. Using cotton wool, wipe this mixture over the scale.

Winter Pests : Snails & Slugs

In the winter rainfall area, these will become quite active and be a problem because of the damp and wet overcast weather in which they thrive. 

  • When checking if you have a problem in your garden don’t just think of seedlings planted, veggies, and plants commonly affected by these slimy critters. Remember that plants like succulents are also prone to slug and snail damage. Look at dense plantings in your gardens as well, they tend to hide in these during the day.
  • Mulching and using abrasive materials like eggshells acts as a deterrent to slugs and snails. 

If you don’t have pets then you can also place a saucer of beer near plants that tend to be attacked. They will drink the beer, become intoxicated, fall into the saucer and perish.

Winter Fungi : Black Spot

Black spot is a fungal disease and a common sight on rose leaves. Citrus fruits and quinces are also affected by a form of black spot.

  • On roses, this fungus is characterised by black spots on leaves where surrounding parts eventually turn yellow. This is followed by affected leaves eventually falling off to the extent that almost the whole plant can be defoliated. 
  • Black spot becomes more prevalent now in winter rainfall areas when leaves stay wet for six to eight hours, which allows spores to germinate. 
  • Fungicides containing copper work very well to treat the problem.


You can also make a homemade fungicide by chopping up 500 grams of onions, garlic, and chives and adding this to 10L of water. Allow this mix to ferment for seven days. Strain and dilute this 1:10 with water and then spray onto plants.

Winter Fungi : Downy Mildew

Downy mildew is a fungal disease that presents itself on roses, vegetables from the cucurbit (pumpkin, cucumber, and gem squash) and cabbage families, onions, peas, grapes and a variety of ornamental plants. 

  • The development of downy mildew is common when temperatures are low and heavy rain or dew is experienced. This is why it is a problem in winter rainfall areas. 
  • The most common symptom is spotting with a greyish mildew forming on the undersides of these spots. 
  • Again, fungicides containing copper work well to treat this problem. 
  • The above Allium (onion, garlic, and chive) spray also works for downy mildew.

Winter Fungi : Damping off Disease

Damping off is a horticultural disease or condition, caused by several different pathogens that kill or weaken seeds or seedlings before or after they germinate. It is most prevalent in wet and cool conditions. In winter rainfall areas this can be a problem at the moment. 

  • Damping off can be reduced by planting fungicide-treated seed directly into the garden. Other preventative measures include using well-drained soil and avoiding the overcrowding of plants. Also, clean out all pots thoroughly before reuse and discard contaminated soil.
  • Cinnamon powder can also be used to prevent damping off by sprinkling the powder onto the seedlings or onto the soil. 
  • There is no cure for damping off once plants are experiencing this fungus. Remove plants and discard. Remove affected soil and clean out pots if plants were in pots.

Winter Fungi : Powdery Mildew

This is one of the most common fungal diseases in the garden. It affects various plants: ornamental, vegetables, and fruit. 

  • The symptom is clear white powdery growth on leaves, stems and flowers, as well as fruit surfaces. Severe infestations can even cause the leaves to curl and yellow and flowers and fruits can become distorted and malformed. 
  • This fungus is more common in wet weather. 
  • Margaret Roberts organic fungicide is quite effective in treating this fungus but you can also use the homemade fungicide recipe described above.

Winter Fungi : Rust

This fungal disease affects a wide range of woody and herbaceous plants. Even though it rarely kills plants, it reduces a plant’s health, vigour, and flower production.

  • Rust diseases occur most often in mild, moist conditions. Rust is spread by spores that are transferred from infected plants to healthy plants. These spores can be transferred either by the wind or by water, which is why rust disease often spreads after watering or heavy rains. Wet surfaces are also needed to cause infections.
  • Rust diseases come in different varieties and can affect a wide range of plants. People often struggle with rust on their roses. It is easy to remember the defining characteristics of this fungus, as it matches its name. Rust plant disease will look similar to the rust that appears on metal items. 
  • Rust is extremely difficult to treat and most times it is best to remove affected plants and put them into sealed rubbish bags and take them to the rubbish dump. You can try using a copper fungicide but this is not always effective.

In conclusion, the above information should help you to solve some of your biggest winter-gardening problems. But please remember to be kind to yourself. You cannot always solve every problem in your garden. If your problems persist or you need further advice, ask for a horticulturist’s advice at your local retailer and they should be able to shed some more light. Or send us a direct message if you have a question for Jessica Ruger, our horticulturist partner.

Now let’s try to keep those critters at bay!

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