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During flowering, rhododendrons are as beautiful as the most attractive shrubs, even roses. In addition, the buds on most species open early, at a time when the garden is dull and many heat-loving plants have just begun to leaf out. Feeding rhododendrons in the spring is very important. And even though the flower buds have been planted since last year, the health of the plant and how the bush will behave in the next season depend on the correct application of fertilizers.
Features of fertilizing rhododendrons
Rhododendron is the largest genus of the Heather family (Ericaceae). The number of species has not been precisely established, since new ones are discovered or separated into a separate taxon every year. Today there are more than 1200 of them.
Wikipedia gives a figure that is half that, but the author obviously took into account only those rhododendrons that were assigned the “accepted” status.Many more species are classified as “unassigned” and are awaiting description.
For few plants, the composition and structure of the soil are as important as for rhododendrons. Feeding also depends on them. If the bush grows in an area rich in sphagnum peat bogs, it will not need to be fertilized. Overly caring owners can reduce crop feeding to symbolic.
Where the soil has a neutral or alkaline reaction, rhododendron must be fertilized constantly. And not from case to case, but by carefully planning the feeding scheme.
Ash should not be used to feed rhododendron. It deoxidizes the soil, just like humus of animal origin. It is because of improper feeding that rhododendrons most often die. When there is a shortage of substances necessary for the culture, and an excess of undesirable ones, conditions are created that are unsuitable for plant life, and it simply dies.
Spring feeding of rhododendrons should contain a large amount of nitrogen. This substance is the main “building” element for plant organisms; it is necessary for photosynthesis, the growth of green mass and flowering. By mid-summer, the need for nitrogen decreases and, in order not to cause a second wave of vegetation on the eve of cold weather, it is excluded from the “diet” of the crop.
Feeding rhododendrons in the fall lays the foundation for next year's flowering and allows the shrub to safely overwinter. Other macroelements – phosphorus and potassium – are of great importance here.They allow the wood to mature, participate in the formation of flower buds, and strengthen the root system.
Soil acidification for rhododendron is especially important on soils with a neutral and alkaline reaction. It is needed even where the pH level is low, but the soil on the site was changed before planting garden crops. There are many ways to do this, the main thing is not to ignore the needs of rhododendrons, otherwise they will stop blooming, will get sick, and as a result will simply die.
How to test soil acidity yourself
Gardeners cannot always say exactly what soil acidity is in their area, and calling a specialist to determine the pH level is troublesome and expensive. In addition, this needs to be done every year, or even better, several times a season.
It’s easy to check the acidity of the soil on your site yourself. To do this, just buy litmus paper. The procedure itself looks like this:
- Under rhododendron bushes at a depth of 0 to 20 cm, you need to take several soil samples.
- The soil is thoroughly mixed, 1 tablespoon is poured with four times the volume of distilled water.
- Leave for 2 hours, shaking constantly.
- Take a strip of litmus paper, soak it in the solution, and compare it with an indicator scale.
This method of determining acidity is very simple, but not perfectly accurate. But it provides objective information about pH levels, and serves as a guide to action (or inaction) for amateur gardeners.
Types of fertilizers for rhododendrons
Now there are a lot of fertilizers on sale that allow you to create comfortable conditions for rhododendrons in areas with any soil.Some of them contain special acidifiers, freeing gardeners from having to adjust the pH level separately. But such fertilizers are usually not cheap.
Meanwhile, it is possible to create acceptable conditions for culture without chemicals at all. True, not everyone will succeed without hassle. So, each gardener must decide which fertilizers to use independently, based on his own conditions and capabilities.
Mineral
Now on sale you can find fertilizers for rhododendrons in any price category, from domestic and foreign manufacturers. It is important to use them correctly, strictly follow the instructions and not engage in amateur activities - it is better to underfeed the plant, then the situation can be improved. If there is an excess of fertilizers, the bush may die immediately, or, for example, if a nitrogen-containing preparation is given in the fall or late summer, it simply will not recover after winter.
Fertilizer for rhododendrons Greenwold (Greenworld) showed good results, which can be used for other heather crops, hydrangeas and lupins. It contains a full range of microelements and is used in the first half of the season - spring and early summer.
The fertilizer for rhododendrons Florovit has a similar effect. Both fertilizers are in the middle price category and are of high quality.
Cheaper fertilizers can also be used. Which ones and how to use them will be described below.
Organic
Supporters of organic farming can do without chemicals at all.For novice gardeners, this can cause an endless stream of questions, because they know two main types of natural fertilizers: ash and manure. And they are strictly contraindicated for rhododendrons.
Here, mulching the tree trunk circle with a layer of 5-8 cm will come to the rescue. But not everything is suitable as a fertilizer. The best materials to not only prevent weed germination and retain moisture, but also feed rhododendrons are:
- Pine needles. But you can’t just take it from the nearest forest if there are crooked or infected trees growing there - along with the litter, pest larvae and pathogens will get into the area. You can take needles only from clean plantings, or buy (ask) at the nearest botanical garden or conifer nursery - there should be enough of this stuff there.Comment! Pine needles are best suited as fertilizer.
- Crushed bark of gymnosperms. Here, again, it is best to use pine. Moreover, mulch, even the smallest fraction, will not work. What is needed is finely crushed fresh bark from healthy trees. So this method of fertilizing rhododendrons is only suitable for those who have a special grinder.
- Peat crumbs, grass, chaff, and leaves performed somewhat worse as fertilizer.
As mulch decomposes, it acidifies and enriches the soil with useful substances, but their supply is not endless. After 2-3 months the layer will have to be updated.
How to feed rhododendron
Fertilizers for rhododendrons in spring can be either organic or mineral. It is important that purchased drugs are specialized. Nitroammofoska or even the best fertilizers for other crops will not work here - they can harm rhododendrons.In the fall, in any case, you will have to use mineral fertilizers.
How to feed rhododendron in the fall
Even if the rhododendron bloomed beautifully, was not affected by pests and diseases, and the bark on the young branches had become lignified by the end of the season and seems to be fully mature, autumn fertilizing cannot be ignored. It depends on them how the crop will survive the winter. And will it bloom profusely next spring?
At the end of summer and beginning of autumn, rhododendron should be given phosphorus-potassium fertilizer twice. Even in an area where pine needle mulch has been regularly changed, this should be done at least once.
You can use a specialized fertilizer for rhododendrons that does not contain nitrogen, but it is difficult to find on sale. And why? There is an excellent domestic preparation, potassium monophosphate, which is used for all perennials. It showed excellent results, and despite the low price, it is no worse than imported fertilizers.
How to fertilize rhododendron in spring
Amateur gardeners often wonder how to feed rhododendron in the spring for lush flowering. It should be noted that if mineral fertilizers are used, they will need to be applied frequently.
And since the buds open early, and the mulching litter does not have time to begin to decompose due to insufficiently high temperatures, the first two feedings of rhododendron in the spring should be done with chemicals, even for supporters of organics:
- as soon as the snow melts, add nitrogen;
- After about two weeks, in April, rhododendrons should be fed with complex fertilizer.
It will be useful for amateur gardeners, who for one reason or another do not have the opportunity or desire to use special preparations, to find out how the crop was fed before.After all, specialized fertilizers appeared not so long ago, and in botanical gardens and nurseries, rhododendrons have always amazed with their lush, abundant flowering.
They were given the following nutrient solutions at intervals of 10-14 days:
- Ammonium sulfate and potassium nitrate - 5 g of each salt per 10 liters of water.
- Urea and potassium magnesium are the same proportion.
Feeding is carried out from April to mid-June, then stops in order to prevent an untimely surge in re-growth of shoots. This will not allow the rhododendron to overwinter safely, and may even lead to the death of the plant.
Foliar feeding
Once every 2 weeks it is useful to spray rhododendrons with foliar fertilizers. You can dissolve preparations intended for soil in water, but it is better to use a chelate complex for these purposes. If amateur gardeners find a special one for rhododendrons, good. Otherwise, chelates intended for conifers or lawns are perfect replacements.
How to acidify soil for rhododendrons
Soil acidification can only be ignored in areas where it already has a low pH. For rhododendrons, the most comfortable level is 3.5-5.5. If the soil has a neutral or alkaline reaction, it is impossible to do without acidifiers - the plants will constantly get sick, wither, and as a result die.
Rhododendrons, which are fed alternately with solutions of ammonium sulfate with potassium nitrate, or urea and potassium magnesium, receive enough acid. The same applies to bushes, the soil under which is covered with constantly renewed mulch from pine needles.
Specialized fertilizers also often contain an acidifier. You can find out whether this is so by carefully reading the instructions.
Starting from mid-June, rhododendrons are no longer given specialized nitrogen-containing fertilizers or self-composed nutrient solutions. Only after this the pH level is maintained by other means.
How to water rhododendron with citric acid
It’s worth noting right away that this method is not the best. But if there is no other way out, watering rhododendrons with citric acid can act as an “ambulance”. Some gardeners constantly moisten the crop with an acidified solution, and claim that they like the result.
A teaspoon of citric acid is thoroughly diluted in 10 liters of water. Before watering the bush, the soil underneath needs to be moistened.
Feeding rhododendrons with vinegar
In fact, watering rhododendron with water and vinegar in the spring is not feeding. A solution of this acid does not contain any plant nutrients. Use vinegar to acidify the soil.
But this is the worst option - the soil deteriorates, and the rhododendron root suffers, so this should be done only as a last resort, and preferably infrequently. It is better to buy a packet of citric acid.
Add 2 tablespoons of vinegar to 10 liters of water and pour over the damp soil.
Other soil acidifiers for rhododendron
It is “other acidifiers” that are best used to bring the pH to the level necessary for the normal development of rhododendrons. These include, first of all, coniferous litter. Pine is considered ideal.
Sphagnum peat acidifies the soil well.It is also used as mulch, pouring a layer of 5-8 cm into the tree trunk circle.
Rules for applying fertilizers
When feeding rhododendrons you need to pay attention to some points:
- Young or newly planted bushes should be fertilized with liquid or dissolved in water preparations.
- Before using fertilizers, you should carefully study the instructions and adhere to the manufacturer’s recommendations.
- Fertilizers containing lime or chlorine should be excluded from the “diet” of rhododendrons.
- Phosphorus supplements are of great importance for crops, especially in autumn, but their abuse will lead to chlorosis.
Conclusion
You can feed rhododendrons in the spring in different ways, the main thing is that the crop does not suffer from a lack of nutrients. There are inexpensive domestic fertilizers that allow you to simultaneously acidify the soil, and quite expensive imported preparations in which the manufacturer has balanced macro and microelements. Organic gardeners can provide their rhododendrons with everything they need by using pine bedding.
