I am a professional gardener in Melbourne and when it was settle just over 150 years ago, many of the immigrants were Britsh and they loved their cold climate plants such as azaleas and hydrangeas. Initially they grew well, but our climate has changed dramatically over the last 150 years, we no longer have the cold winters or wet springs we used too. Azaleas are native to Asia, Europe and North America and are perfect for English gardens but in our hot Australian gardens, not so good. They love cool roots and lots of moisture with lots of rich organic matter. Now you mightn’t know that Melbourne has experienced 12 years of drought with restrictions that only let us water twice a week. Our spring and summers have been longer and hotter, thus really stressing out our azaleas and hydrangeas. Stressed plants aren’t good as they attract pests and azaleas are no exception. A sick azalea is a beckon to pests and one of the most devilish is the old thrip – so tiny – yet it does so much damage.
Thrips are a sap sucking insects, with long blackish bodies and so small about 1cm long that is very hard to see them. They suck the sap out of the leaf, causing it to go silvery all over and this can never be repaired. The plant can live with the silvery leaves but they look awful. There is also the two-spotted mite that sucks the sap out of the leaf and again leaving it with silver blotches.
Azaleas and How to revive hydrangeas are surface rooted, this means that the majority of their roots lie just a few centermeters under the soil. As the moisture evaporates from the soil and transpires out of the leaves, the roots try to replace the water lost but unfortunately there isn’t any soil moisture available and thus they become water stressed. This is a huge problem over summer and can kill many different species of plants. Leaves can become sunburnt or scorched and these are areas where the cells have been irrevocably damaged. The rest of the leaf can continue to carry out its metabolic funtctions. But if the entire leaf is destroyed, then the leaf and sometimes the entire plant can’t be revived.
Both species do well on clay soils because they are rich in nutrients and hold onto their water better than sandy soil. If you have sandy soils, then I suggest you incorporate lots and lots of compost and animal manure. You will need to do this every year, as sandy soils revert back to its original structure very quickly if it is not constantly being improved.
It is also important that azaleas and hydrangeas are planted in the right position – morning sun and afternoon shade. Morning sun is gentler and not as intense as the harsh afternoon sun. If they cop the afternoon sun, then they are going to struggle. Azaleas also do well under deciduous trees. But it is essential for flower development that both species receive some sunlight.
With some effort and forethought you can prepare your plants for summer. It may not stop them wilting or being water stressed completely, especially if it is really hot, but it may help them survive, waiting for the cooler weather of autumn.
Suggestions on how to prepare your plants for summer:
- In early spring incorporate lots of compost and animal manure as it has good water holding capacities
- Apply lots of leaf mulch, azaleas love it.
- Water around the drip line (edge of the canopy) a wetta soil product. It helps absorb moisture into the soil.
- Incorporate water holding crystals into the soil around the plant. They swell up and hold the water, making it available to the plants roots
- Mulch the garden bed
- Use any spare water you have collected on the azaleas and/or your hydrangeas
Hint: on very hot days, pop an old beach umbrella over the azaleas and hydrangeas to protect them from the harsh mid-day sun.
Growing Azaleas in Pots
If you have your azaleas in pots, you need to be very aware that terracotta dries out very quickly and black plastic pots absorb heat. The soil in the pots heats up and literally cooks the roots. If the damage is severe, it can kill your plant. When planting them into pots, it is a good idea to use the best quality potting mix and add compost and water holding granules to improve the watering holding capacity of the potting mix. The good thing about pots is you can move them around and even bring them inside (if they are not too big) on really hot days. I have a standard azalea and in summer I move it from the backyard to the front yard where it gets no direct sunlight. Behind it is a brick wall and this protects it from the hot western sun and the northerly winds that are notorious in summer. I also put pea straw mulch on my pots and I find that that really helps cut down on the evaporation.
I love hydrangeas, especially the blue flowering ones, but they don’t like Melbourne’s summer climate anymore either. They are native to southern and eastern Asia and North and South Amercia in climates that have cooler summer temperatures and lots of moisture. As our Australian summer (especially southern Australia) have got hotter, the old hydrangea has really taken a battering. They are good plants in that they are indicator plants which means they are the first to wilt and let you know the soil has dried out. They also recover really quickly once they have been watered. But they are not a plant I would recommend today because they take so much water to keep them alive and looking good. For those who have old gardens with them in it, follow the above suggestions and this will help you manage them over summer.