Intermittent mist was a great revolution in propagating plants. It enabled the propagator to quickly and cost effectively produce many plants at a time. However, with the benefits comes negative impacts on the nutrients that are within the cuttings. Not knowing how your cuttings are performing can cause them to form roots very slowly, not form roots at all, or cause them to die.
Unrooted cuttings rely on their reserves of nutrients to help the cutting survive until they form roots. Until the cuttings actually form roots, they do not absorb new nutrients from the rooting media. The cuttings get these reserves from the parent stock plant the cutting was originally taken from.
Cuttings absorb nutrients from the rooting media or potting media once the roots have formed, but until the formation of roots has completed, leaching of the nutrients from within the cutting is possible. Hardwood cuttings tend to be more susceptible to leaching than softwood cuttings because the softwood cuttings retain more nutrients in their cell walls which make the nutrients harder to leach out. The level of nutrients in the cuttings is highest when first taken from the stock plant, declines as the cutting is rooted, and increases again once roots develop.
Nitrogen, phosphorus, calcium, magnesium, iron and boron are the most likely nutrients to be leached out of cuttings while they are under mist. The result usually will be first seen as foliar deficiencies. These deficiencies may be yellowing of the leaves, spotting, and other symptoms.
Most small plant propagation nurseries do not have the facilities to properly test for nutrient leaching. So what should you do?
- Be sure the stock plant you will be taking your cuttings from is healthy and well fed with fertilizer before actually taking the cuttings. This will ensure that the cuttings you do take will have the maximum amount of nutrients in them. Ensuring the cuttings have high nutrient levels will increase your odds of them surviving past the critical stage of when the unrooted cutting turns into a cutting with roots that is able to absorb new nutrients from the soil.
- Do small scale tests and record your findings. Add a small amount of slow release fertilizer to your rooting media. This will ensure the cutting will have nutrients available when it needs them. Too little fertilizer is better than too much! Note which plants do best and the amount of fertilizer you used. Good record keeping will enable you to duplicate the process when you find the one that works. Your records will also keep you from making the same mistakes over and over again!
- Do not over mist. Over misting will leach the nutrients from the cuttings much faster. You want to keep the leaves of the cutting moist but not too wet. On the other hand, never let the cuttings wilt during the misting process.
Ok, I can hear you thinking…why not use liquid water-soluble fertilizer like Miracle Grow? A few reasons.
- It leaches out of the rooting media quickly.
- Some cuttings do not do well when the fertilizer is applied to the leaves or stems.
Paying careful attention to your stock plants nutritional health before taking cuttings is one of the easiest methods you can do to be sure your cuttings have the nutrients available to them during the rooting process.