Angus Stewart, kangaroo paw and wicking beds
In this article we explore tips for growing the best Kangaroo Paw from master breeder and horticulturalist, Angus Stewart. Wicking beds are excellent for growing edible plants, but they can also be used to great advantage with some native plants, like kangaroo paws. This article outlines:
- The advantages wicking beds provide for growing kangaroo paws
- The optimum soil mix for growing resilient and bountiful Kangaroo Paws
- The benefits this can have for other commercial growers, home gardeners and council gardeners planting Kangaroo Paws
About Kangaroo Paw
Kangaroo paws are rhizomatous perennials, meaning they are long-lived plants and grow from a tuber-like rhizome underground. The kangaroo paw family comes from southwest Western Australia and has two genera in it:
- The genus Macropidia has only one species in it, Macropidia fuliginosa, commonly known as the black kangaroo paw.
- The Anigozanthos genus has a number of species within it, and these are the kangaroo paws that you will commonly find in nurseries and that are used for breeding new types of kangaroo paw. There are a number of species and forms in the Anigozanthos genus, including the dwarf and tall kangaroo paws in a range of flower colours. The floral emblem of Western Australia is Anigozanthos manglesii, the red and green kangaroo paw.
It’s a common perception that Australian natives don’t need much water or nutrients to perform well. This is certainly the case with some species. Indeed, Kangaroo Paws are a drought-tolerant plant and can resprout from rhizomes – however they really thrive and flower best when given optimum levels of water and nutrients, rather than simply left to their own devices. This is according to Angus Stewart is a horticulturalist and plant breeder who has been working with kangaroo paws for decades – and in recent years with WaterUps wicking garden beds.
Plant breeding involves many hours of painstaking labour, and if plants become stressed, then large amounts of work can be lost. To look after his invaluable collection of breeding stock, Angus was looking for a system that would be as safe as possible in terms of keeping plants healthy. He found that in WaterUps.
Reduces Black Spot
Kangaroo paws are less susceptible to black spot when they have ideal levels of water and nutrients. The wicking bed system also helps to reduce black spot by delivering water from below via capillary action, meaning there is less surface moisture which helps to reduce the incidence of black spot. Angus has seen this in his own kangaroo paw collection – a collection that includes his prized breeding stock.
Kangaroo Paws are sensitive to overwatering which can cause root rot and crown rot so it’s important not to overwater and to ensure adequate drainage around the roots. The WaterUps systems provides the optimal watering system as water is wicked up through perlite in the wicking cells and the lower layers of soil, providing the right amount of moisture and aeration. Using WaterUps, plants are watered via the top inlet once the reservoir below is empty, and there is an overflow drain once the reservoir is full. Using WaterUps in raised garden beds, gardeners often only need to water their plants about 20% of the time of their previous watering schedule (depending on climate and season)
Prevents Plant Stress
Angus has amassed quite a collection of important stock for his breeding work and in recent years has been trialling the WaterUps wicking beds as a way of keeping these valuable plants in peak health. When growing plants for breeding work, it is important to maintain optimal levels of water and nutrients to ensure plants don’t get stressed.
Plants can become stressed in two main ways: water stress and nutrient stress.
- Water stress is quite obvious, as you can see the leaves of plants wilting. Plants that have experienced water stress generally bounce back when rehydrated, but if the plant is under water stress for a longer period, it may reach what is known as permanent wilting point. Permanent wilting point is the stage at which plants cannot be rehydrated, even when soaked in water for 12 hours. However, any amount of water stress can be damaging to a plant, as it alters the way the plant grows and these effects are not necessarily reversable.
- Nutrient stress can be harder to spot, but it makes plants more susceptible to diseases and impacts the overall health and vigour of the plant.
Water and nutrient levels are also correlated in that soil needs to have enough moisture in it for nutrients to be taken up by the plants.
WaterUps provides Optimal Soil Moisture
For Angus the WaterUps wicking beds has proven to be an excellent solution for maintaining consistent moisture, but the other part of the equation for healthy plants is maintaining optimum nutrient levels as well – and this is dependent on the soil and feeding the plant
The best growing medium
To maintain optimum nutrient levels in the wicking beds, the growing medium is vitally important. The single-cell WaterUps unit is a closed system, so all nutrients need to be added into the planter. This is best achieved by selecting a high-quality growing medium when filling the planter, as well as adding slow-release and liquid fertilisers as required.
In order to find out what kind of growing medium works best for the kangaroo paws, Angus has been trialling different potting mixes and observing the results with his breeding stock.
A recent trial involved growing kangaroo paws in WaterUps planters using two different potting mixes: an experimental mix containing biochar (further details in Footnote below), and a high-quality premium Australian Standards potting mix.
There were 10 single-cell WaterUps planters of each mix, so 20 containers in total. Angus found that the experimental mix with biochar was not delivering enough nutrients to the plants. This was abundantly clear when they were compared with the planters containing premium mix. The plants in the premium mix could not have performed better, while the experimental mix was inadequate in terms of providing sufficient nutrients. The premium mix delivered excellent results from both a growth and breeding point of view.
As you can see from the below photograph – the plants were twice as high and at least four times as dense. – this meant more plant to be divided and harvested – as well as more flowers and seeds for harvesting.
While some natives, such as banksias, need very well-drained soil and low phosphorus soil mix and fertiliser to grow well, kangaroo paws are actually gross feeders. In other words, the more nutrients they are given (up to a certain level), the better the growth and flowering.
More Flowers / Longer Lasting Flowers
Angus found that due to the optimal soil moisture conditions in the WaterUps wicking beds, he was able to achieve greater flower productivity and longer lasting flowers.
Making the most of Wicking beds
The experiment clearly showed that the advantages of the wicking bed system for kangaroo paw growing can be fully realised when using a great potting mix, so that plants do not get nutritionally stressed. The capillary watering system ensures that plants don’t suffer water stress, while the potting mix needs to ensure that plants don’t suffer from nutrient stress. This is particularly the case for plants grown in containers, as they do not have any sources of nutrients beyond what is put in the container.
From a professional horticulturalist’s point of view, the WaterUps system is an excellent way for Angus to keep his breeding stock at its full potential. Firstly, it is a great system for maintaining such a valuable collection. Secondly, kangaroo paws perform very well in the wicking bed system, despite perceptions that they thrive on neglect. Thirdly, it is not just the consistency of water that is important for plant health, it is also nutrient levels in the soil: when both are at an optimum, plants will perform at their best.
Public Garden Implications
Kangaroo paws are a popular plant choice for council gardens and verge planting across Australia. (see pics below). To this end, WaterUps wicking cells and our Sub-irrigation channel can be used in creating garden beds that will require less watering from council trucks, while delivering healthier planters and longer lasting blooms. They will also help ensure more resilient plants, helping council’s planting and maintenance budgets go further.
Biochar is a charcoal-like substance that’s made by burning organic material from agricultural and forestry wastes (also called biomass) in a controlled process called pyrolysis. Although it looks a lot like common charcoal, biochar is produced using a specific process to reduce contamination and safely store carbon.
The results of the experiment show that biochar in and of itself doesn’t necessarily improve plant health, and there are a few reasons for this.
Biochar is a highly variable product, and the properties it has depend on what kind of biomass was used to produce it, and the conditions under which the biomass is burned (or “pyrolised”). One important aspect of biochar is that it needs to be “activated” in order to have the beneficial properties ascribed to it. “Activation” is a physical or chemical process that expands the surface area of the charcoal and increases its adsorptive properties, thereby increasing its capacity to store water and nutrients for plants to take up when needed. Biochar is a site for the activity of beneficial microbes, but those microbes also need nutrition to be beneficial to plant growth.
Biochar has great potential as a beneficial addition to soils that improves soil quality and plant health, but there are a few factors that need to be taken into account when using it. The main factor to consider is that biochar in and of itself is not a fertiliser, so it has no nutrient value on its own. Simply adding biochar to soil may not produce beneficial effects in a closed system with inadequate nutrients. Biochar needs to be “charged” with nutrients and “inoculated” with beneficial microbes in order to reach its full potential as a soil conditioner. In this experimental potting mix, the biochar had not been charged with nutrients, and the mix did not contain enough nutrients to enable the biochar to reach its full potential. Angus is going to do a subsequent trial with activated and charged biochar, and we will report on those results to see how the benefits of biochar can be fully harnessed. Biochar can be charged and inoculated with worm juice or a product called POPUL8 from Australian fertiliser company Neutrog, amongst other things. When biochar is produced and used in the correct way, it is a powerful tool for sustaining plant growth and sequestering carbon in a stable form.