One way to manage a potential problem is to put strategies in place to prevent the problem before it occurs. To be sure, this does not help with problems already in place, but it prevents you having to deal with new ones cropping up, and so it is with weeds! Plus, of course, if you are just starting out these strategies can save you a lot of trouble down the track by keeping your weed problems to a minimum.
Weeds make their way into our landscapes three ways –
- Weed seeds or runners are imported in things we buy for our garden,
- Weed seeds are brought onto the property by natural forces such as wind, water or transport by animals or ourselves (think cobblers’ pegs in your dog’s coat or your socks!), or
- They are pre-existing.
Acknowledging number one above, that a way of preventing weed infestations is by not importing weeds onto your property in the first place, there are three main ways in which this can happen, ie buying in –
- Seeds,
- Plants,
- Mulches and other soil improvers
Clearly this may be something we do a lot of, particularly in the establishment phase of gardening, so it is important to understand what the risks are and how to address them.
1. Seeds
Problems
There are a couple of potential problems when we buy in seeds. The first one being that the seeds we buy in may contain a proportion of weed seeds which we then sow, thinking we are getting a crop but we are also introducing a weed(s).
The second problem may be associated with the plant themselves. Many years ago I was looking at sowing some grain in the back yard for our consumption, but I had tried our go-to – wheat – without much success due to lack of land. I had subsequently read about a South American grain called amaranth (this was back before the internet, yes I am that old!) and thought it would be worth a go. I got hold of some seed from a seed supplier planted it out and waited for it to do its thing. Well, it turns out that grain amaranth produces huge numbers of tiny (and edible) seeds that get EVERYWHERE! It took me ten years to eradicate the stuff from the back yard, although we still get some weed amaranth cropping up occasionally.
This is weed amaranth, but the theory holds!
The strategies
A. Only buy seed from reputable suppliers – preferably your local seed savers or permaculture group or from the smaller sellers of organic seed available on line, rather than mega-commercial seed suppliers. They should also be open pollinated so you can grow from your own seed, the safest option.
B. Start your seed in punnets rather than direct sowing, that way you can keep an eye out for anomalies. You should only plant out seedlings after they have reached the true leaf (as opposed to seed leaf) stage, where weed leaves should look different from the plants you are wanting to grow.
Our system that uses punnets and newspaper pots gives us plenty of time to spot 'non-standard' seeds!
C. Do your research – before you obtain and start sowing seeds of a plant which you are not familiar with, check out the following questions: Are they easily pollinated? Do they produce copious amounts of seed? Do they reproduce by roots, tubers, corms or runners as well as seeds? Do they grow vigorously and outcompete surrounding species? A yes answer to any of these does not necessarily mean a problem, but if you are committed to the plant then you may need to work out how you are going to control it, before sowing the seeds into your garden.
2. Plants
Problems
New plants being introduced to your garden may bring problems with them or they may be the problem. When you bring plants in pots into your garden, the soil in those pots may contribute weed seeds as well as the plant for which you paid.
Sometimes though, the plant which you have bought may have weed potential. A popular climbing plant people get for their gardens is jasmine, it is easy to grow, attractive and the flower has been used medicinally as well as to extract a material that can be used to encourage plant cuttings to root. It is, however, incredibly invasive and once you have it you’ve got it for life.
Jasmine - beautiful but dangerous!
Unfortunately, the weed potential may also be from a part of the plant itself. As an example, many years ago we bought a couple of passionfruit vines to go at the back of the house. They were grafted ‘Nelly Kelly’ variety and while we didn’t know it at the time, the rootstock they use is a hugely invasive pest. The leaves look different and while it does produce a fruit of sorts, the fruit isn’t edible. It has ensconced itself under the back deck and we are still dealing with it.
Passionfruit 'Nelly Kelly' rootstock, poking its head up to see if the time for takeover has arrived!
The Strategies
A. when buying deciduous shrubs or trees including fruit trees consider buying them bare rooted, while they are dormant. Bare rooted plants do not bring any foreign soil into your garden and so cannot be responsible for bringing in weed seeds.
B. When buying in perennials which are not bare rooted, consider root washing. The process should be carried out when the plants are dormant and during the cooler times of the year to prevent heat stressing the plants involved. As the name implies, remove any pot or plastic bag and place the soil covered roots into a tub or bucket of water, soak for 10 minutes then gently agitate the roots to remove any soil. If the plant is root bound the roots can be teased out to spread them better. Once the soil has been removed, replant into prepared ground, water with Seasol and mulch. Keep the plant well-watered until it has recovered. The soil and water mix, which will contain any weed seeds, can then be disposed of.
C. Do your research – before bringing any new plants, especially perennials into your garden check with any experienced gardeners you have access to, or gardening groups on the internet to see if there are any undisclosed problems. Also be aware that phrases like ‘fast growing’ or ‘easy to grow’ in advertising the plant may mean the plant has weed potential.
3. Mulches and other soil improvers
The problem
We mainly use wheat straw mulch, and as a result there are some wheat seeds that will get through and germinate. This may or may not be a problem, depending on your point of view. You may wish to let the wheat come up and then ripen so you can harvest it, or it may just be another weed for you.
Years ago I used to get a locally grown grass hay to use as mulch, produced by a local farmer. Being produced locally meant fewer kilometres it had to travel, which was a good thing, but it also left me with the gift that keeps on giving – stinging nettle! It appears that stinging nettle was part of the hay and they had viable seeds. I do have uses for stinging nettle but they are still capable of surprising me when I go to harvest a veggie form the patch.
Animal manures are a great source of fertiliser, but depending on the animal and their diet they may contain weed seeds. Also commercial organic fertilisers, soil conditioners and other soil amendments may contain weed seeds, although hopefully not, but anything is possible.
The Strategies
A. Use chooks - We have a separate chook shed for the older birds that do not produce many eggs, we call it the retirement village. All of our straw mulch is put into the retirement village where the chooks dig through it, break down the long stalks, mix it with manure and eat any wheat seed still mixed in with the straw, so this process provides us with a number of advantages.
Wheat straw, worked over by chooks, does the job as weed free mulch for us.
B. Mushroom compost - Another strategy is to use spent mushroom compost. Due to the nature of how it is used (initially sterilised, kept in low light conditions) it is unlikely to hold any viable weed seeds. Also, on the plus side, spent mushroom compost can produce a second flush of mushrooms under the right circumstances. The compost would not produce enough to be economically viable for the mushroom farmer, but can provide a nice side-crop for us amateurs.
C. Composting - take the amendment, particularly if bought in bulk, hill it up and leave it in the rain to compost for a bit. Any weed seeds will germinate during this time and the plants can be removed. This process is also beneficial for cow or horse manure where the animals may have been wormed recently, and the composting allows the wormer to break down, so that there will be no problems with earth worms being affected.
Conclusion
There are quite a number of ways that weeds can get into our gardens, there is no need to make it more difficult by importing them ourselves. Before bringing any seeds plants or other garden related materials, do the research and avoid the weeds where possible, and then select any strategies for treatment which are appropriate to your situation!
Other articles in this series:
