I remember years ago when this site was begun how much difficulty there was in planting trees and shrubs. There is sheet limestone everywhere and planting holes were actually blasted.

Chamelaucium 'Meringur Mist'

Chamaelauciums (Geraldton Wax) have a habit of becoming a little yellow in the foliage when the soil alkalinity is too high. This one was looking very good.

The garden soil has certainly been improved and I was surprised to see a few plants there which usually take on a yellowish tone in the highly alkaline conditions actually coping well with the conditions. It proves that the high pH situation can be improved with some attention given to good garden practice. In this case, garden beds have been raised and composted materials added and mulch has been applied over the years.

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Verticordia plumosa (Feather Flower)

We had unseasonal fierce, hot winds and temperatures last week and a few of my stock plants were scorched badly. A couple of pots had become non-wetting so that when I watered the water passed straight through the pot in channels and also ran down the sides between the pot and mix. This water repelling can be treated with a soil wetter and I used a granular one which has been very effective.

However, in ‘Gardening Down Under’, Kevin suggests that potting mixes are designed to be used in pots to 125mm across and that clean soil should be used in tubs 225mm and larger. I have been thinking about this. I have a load of sandy loam and I think I will try a 50:50 mix of loam and potting mix in the large pots. This way I will still get reasonable drainage and water retention. It won’t stop the pots from heating up. I will need another strategy for that. The other problem is the weight of the pot. At least I will not be wanting to move them often.

The plant in the photo is one of the forms of this Feather Flower. These are sought after by florists. I have never been game to try them in the ground here, as in the wild they grow in fairly deep sand. This would give them very good drainage. Whether the sandy loam/potting mix mixture would work for them is debatable. I want to make a raised bed to try them as well.

He is not only practical in his approach. He also gives the science behind the practical measures he recommends.

With the drought conditions in Australia at the moment, any information about efficient use of water is welcome. There are a lot of recommendations and reasonings in this book which make sense.

Instead of speaking in general terms about soils, he asked the audience what they would like him to discuss. Well! My first question was about dealing with highly alkaline soils. Bless the man, he spent quite a while discussing strategies.

As Kevin said, the obvious solution is to use those plants that don’t mind those conditions. However, for the rest of us who want to try other plants, he offered some possible solutions to try. One I think is a distinct possibility. Under the drip line of the plant make 3 or 4 holes (depending on the size of the plant) and fill with a mixture of cocopeat or potting mix or peatmoss and ferrous sulphate (10 litre cocopeat to 1 cup ferrous sulphate) and cover with a layer of soil.

As an extension of this, I wonder if it would also work to remove the soil from the planting hole, place the plant, add the peat mix to the soil and back fill with it. It is worth experimenting.

In the previous post Make New Plants… By Taking Cuttings, I mentioned obtaining a propagating mix. I have had to compromise with what is available locally. The basic idea of a propagating mix suitable for cuttings is to have excellent drainage, one that does not compact with watering, and maintains some moisture.

Traditionally, coarse sand mixed with peat moss was used. The difficulty is where does one get coarse sand? One of the potting mix companies now markets bags of coarse propagating sand. Whether you can buy it locally is another matter. Other ingredients readily available are blocks of coco peat (more environmentally friendly than peatmoss), vermiculite and perlite both of which are used in hydroponics. My compromise is a mixture of a reasonable bark based potting mix, coco peat and either perlite or vermiculite, in about equal proportions and moistened.

The main thing to do is to work on a recipe and if it works continue to use it. The most important consideration is to use clean ingredients.

Equally as important is to always mix the ingredients in the open and take care when opening bags of potting mix. Perlite floats. It can be a pest to use. A mask is a good idea as some people have been known to contract Legionnaires disease from dry potting mix floating in the air. Keep potting mix moist rather than allowing it to become powder dry.

No.2 of a series on Propagation

Result? Soil with a pH of say 7.5 (I didn’t want much!) is like hen’s teeth around here. The landscape supply place had three lots for me to choose from, all them within the range of pH 8-9. One a loam, another, loam with chook manure added and much favoured for using to grow instant lawn, and a sandy loam mix. I went home feeling quite disheartened especially when the fellow said that they went looking for acid loam and found that it was loam with turkey manure in it to make it acid! What hope is there for we country folk!

End result is that I opted, after some thought, to get the loam thinking that at least is does not have limestone rubble in it. I will still need to work on it with manure and compost and probably sulphur. This could be an interesting experiment.

The soil here is mostly very alkaline. Some areas of the town and outlying districts go down to neutral. The soil structure  is quite good apart from patches of ‘non wetting’ or water repellant sand. It is the limestone rubble that is the problem. At least the drainage is good. None of the books will say what plants will adapt to these highly alkaline soil conditions. In fact there are many plants which will grow happily in alkaline soil, even though the books do not say this. It is the highly alkaline soil which makes life a little more difficult. It has to be a trial and error situation. So my list will reflect what I know to be true.

It is worth getting the soil tested. A test kit costs something like $25 and will last for years. If there is an opportunity to have soil tested at a plant sale, take advantage of the offer. Sometimes plants which are acid soil lovers will grow in alkaline soil, even if not to the ultimate size that is listed. Others will look very yellow and deteriorate. There are remedies which will improve this, like iron chelates or sulphur watered in to the soil surrounding the plant. Follow the directions  on the container.

In poorly drained soil it is worth raising the level of the soil by creating small catchment areas and adding the soil to one side in the form of a mound. Planting on the mound will make an amazing difference to some plants. I have heard that the raised area will also decrease the effects that high alkalinity has on some plants.

I will begin the list tomorrow.

Good gardening practice will always give good results for planting any types of plants, and Australian natives are no exception to this rule.

1. *Weed control is most important. Remove all weeds from the area to be planted. Be aware that cultivating the soil often will encourage weeds to establish. (On the other hand some native grasses will establish on uncultivated soil).

2. *Prepare the soil by forking to at least the depth of the root system, plus half again, and a diameter of 30-50cm (12-18inches) depending on the pot size.

3. Dig in whatever well rotted organic matter you may have, or keep it to apply to the soil surface.

4. I find it a useful thing to fill the planting hole with water and allow the water to drain away. This not only gives moisture in the subsoil to encourage roots downwards, but enables you to check the drainage of the area.

5. Create a raised planting site by bringing in soil from another area of the garden, if poor drainage is a problem or

6. Add gypsum to the soil if water seems to sit too long in the planting hole. About a kilo per square metre is recommended on poorly draining soils ie those that are mostly clay.

7. If water sits on the surface and seems to “bead”, non wetting soil is probably the problem. Buy a suitable soil re-wetting agent and follow the directions on the container. These are usually added after the planting is done.

8. *In general it is a good idea to soak potted plants in a bucket of water with some soil wetting agent added to it just before planting. (Unless you know for sure that the pot already contains this.) Soak long enough for bubbles to stop rising.

9. Adding fertilizer to the soil immediately below the plant can be a good thing. Use about a tablespoon of slow release fertilizer suitable for native plants, or use blood and bone added to the soil used to put around the plant in the planting hole.

10. *When placing the plant, create a small depression in the soil to act as a water catchment for rain or as a dam for hand watering.

11. *Plants need to be established by regular watering around the roots for several weeks, then weekly watering then leave greater intervals, depending on the amount of rainfall received. Don’t expect the plant to survive on natural rainfall if autumn rains have not begun in your district.

12. *Mulch the area surrounding the plant, keeping the mulch back a little from its stem.

13. *Use inorganic mulches like small sized gravel or sand that is free of weed seed.

14. *Or use organic mulches which will break down over time and need replenishing, but in doing so will add humus to the soil.

15. *Suitable organic mulches would be bark or wood chip, pea straw, rotted lawn clippings, or other rotted vegetable material or waste material.

The points marked * are the minimum that should be done.

I measured the pH of the soil at a number of locations over our 5 acres (2 hectares). Is it any wonder the fruit trees have not done as well as I had hoped. The pH is 8+ to 9+ which is highly alkaline. The quality of the soil varies from sandy loam, to limestone rubble to non-wetting mallee sand. There used to be a strawberry farm on our property, so the structure of the soil is not too bad at all.

My usual reaction to someone who says “that won’t grow on your block of land” is to attempt to prove them wrong. I don’t think I am alone! A lot of plants grow very well in alkaline soil. Some plant species will grow reasonably well, but do not achieve the ultimate size. Others sit and “sulk”, and others struggle to maintain good leaf coverage. Of course some of the most desirable plants (in my eyes) are the ones that are native to areas of acid soil! It is amazing how adaptable Australian native plants are.

When I began writing this piece I wondered if I really understood the science behind pH of soils, so I detoured to find some more info. I am glad I did. I realise that I should have been using iron chelate or iron sulphate more diligently on some plants and would have far better growth by now. Some homework to do later this week.

For more information on soil pH see the ASGAP web page Understanding Soils and Nutrients.