Traditionally trees and shrubs are planted anytime between October and April providing the ground isn’t waterlogged or frozen solid. Spring is the ideal time to fertilise shrubs just before the new growth begins as nitrogen fertiliser has the strongest effect on plants approximately one month after application. However, like most things in the garden it is weather dependant and if there are heavy spring rains, wait until they have passed as heavy rainfall can leach fertiliser out of the soil before it has had a chance to take effect.
Shrubs are so useful providing endless landscaping opportunities by either adding height, colour, texture or by creating a living divide between areas within the garden that can be evergreen or change with the seasons. No matter what type of shrub you choose there are a few golden rules to follow when planting. It is so important to ensure the area you want to plant is enriched and ready for planting. This can be done by adding a soil conditioner (such as revive compost or mushroom compost 100mm in depth) over the surface area of where you want to plant and cultivate it into the soil to improve the soil structure and base fertility. First of all, ensure that the shrub is thoroughly watered or placed in a bucket of water for about 20-30 minutes but allow excess water to drain before planting. Dig a square hole that measures twice the width and depth of the existing container or rootball; the Niwaki Golden Spade will make light work of this. Remove the shrub from its pot, tease out some roots to encourage growth and place in the hole ensuring that the top of the rootball is the same level as the surrounding ground. Before infilling completely, you can add some fertiliser and moisture retaining tree bags (Botanic Pax) in the hole approximately two thirds up so that the nutrition will dissipate around the roots rather than underneath. Continue to fill in the gaps around the newly planted shrub with the soil mix set aside from the hole earlier and firm it down to remove air pockets with the heel of your boot. Water in well with at least one full watering can and then top off with mulch or bark chippings (such as composted bark fines or spruce ornamental) to reduce weeds and retain moisture.
Types of Feeds and Fertilisers
There are four types of fertilisers: pellets, granules, liquids and powders which are used to improve plant growth. It is a general rule of thumb that the faster growing the plant/shrub then the more beneficial a fertiliser will be. Fertilisers are also used when a plant is showing signs of nutrient deficiency (discolouration, yellowing leaves or a general change in overall health) and good soil health is just as important as applying topical fixes of fertilisers/feeds. Maintaining healthy soil and pH levels by forking in organic matter creates space for air pockets and drainage. This enables the roots to access nutrients and with the addition of soil conditioners, will help to prevent nutrient depletion.
There are two main choices of fertilisers; organic and inorganic. Organic fertilisers are those which are derived from plants or animals and inorganic are synthetic/man-made. Organic fertilisers tend to be slower acting as large organic molecules need breaking down by soil organisms before the nutrients can be released into the soil for the plant to then absorb. Examples of organic fertilisers include: blood, fish and bone, nettle feeds, poultry manure pellets, seaweed, liquid comfrey, well-rotted animal manure as well as hoof and horn.
Inorganic fertilisers are generally more concentrated and faster acting. This is because they do not need to be broken down in the same way as organic fertilisers due to their composition of synthetic/ artificial plant nutrients or naturally occurring mined minerals. Many of these off the shelf fertilisers are aimed at producing instant results and would need repeated applications. However, this type of fertiliser can result in the plant leading a boom and bust life where it is fed and then goes hungry which often leads to stress and poor growth long term.
The application of a fertiliser is perhaps most critical at the time of planting or repotting as they provide the roots direct and easy access to the micro-nutrients and moisture that are needed to support good growth.
A granular fertiliser that is a blend of both organic and inorganic ingredients will provide a slower release of nutrients and will therefore benefit the plant over a longer period. Another benefit of this type of fertiliser blend is that with fewer applications needed it encourages and promotes healthy sustainable growth allowing the plant to become self-sufficient (although it is recommended that an annual feed is used to maintain health and performance). An example of a blend is Stripy Green Fertiliser which not only can be used on lawns but has all the micro-nutrients needed to promote good plant growth as an annual feed.
Summary of Fertiliser and Feed Application
The type of fertiliser you use will determine the application method. The most common methods include top dressing, base dressing, watering on or foliar feeding. Top dressing is probably the most common and is usually done in the spring. Top dressing is the application of fast acting fertiliser to the soil surface and around the base of plants. Base dressing is the incorporation of fertiliser directly into the soil before potting/planting/sowing. Watering on is as the name suggests and is for liquid or soluble powders or granules that are diluted or dissolved in water before watered onto the base of the plant. This type of fertiliser can give an instant boost as it is easily utilised by the roots of the plant and are usually used for bedding plants, glass house crops or pot plants. Finally, is foliar feeding which is the application of dilute fertiliser directly to the leaves of the plant. This type of feed is generally used as an emergency treatment to correct nutrient deficiencies or fast acting supplementary feed. The absorption is greatest on new tender leaves and on the underside surface. Caution should be used not to apply foliar feeds in bright sunlight due to the risk of leaf scorch.