Boost Your Hydrangeas with Urea Nitrogen Fertilizer
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1. When to Use Urea Nitrogen Fertilizer on Hydrangeas2. How to Use It3. Benefits of Using Urea in The Fall4. Combining with Other Fertilizers5. FAQ6. Conclusion
Urea fertilizer, commonly used in gardening, contains around 46% nitrogen and is the primary source of nitrogen fertilizer.
Plants need nitrogen to grow well. Nitrogen helps plants keep healthy by strengthening their leaves, stems, and buds. It also helps the leaves to absorb more sunlight. So, when we use urea nitrogen fertilizer, it helps the plants grow better with lush green leaves and beautiful flowers.
Hydrangea is a highly ornamental shrub. From late summer to early fall, the nitrogen content in its leaves can be as high as 50% of the total nitrogen of plants. As the leaves naturally fall off, 50% of the nitrogen in the leaves will transfer to the stem and roots. The hydrangea will use the nitrogen stored in the stems and roots for new growth in the next growth cycle.
1. When to Use Urea Nitrogen Fertilizer on Hydrangeas
After the blooming period, we will prune the hydrangea stems, leaves, and flowers from early July to mid-August. However, the hydrangea leaves did not fall off naturally at this time and were still green.
Hydrangea loses much nitrogen when we prune the plant leaves before they naturally fall off. It is one of the reasons why some hydrangeas do not grow well in the next year after pruning. At this time, we use urea to give enough nitrogen to help the plants store enough nitrogen for their growth in the next year.
In short, after finishing pruning from July to August, we need to foliar spray urea nitrogen fertilizer to hydrangea.
2. How to Use It
We only need to spray hydrangea leaves with urea solution in the fall.
- Dosage
The urea content in the water solution will determine whether it is effective and whether plants are safe. If the content is too low, it will not be able to replenish the nitrogen plants need. If the content is too high, it will burn plants.
Diluting urea with water 1500 to 2000 times is safe for hydrangea. In other words, we can mix 2.5 grams of urea with a gallon of water as foliar fertilizer.
- Spraying method
- Use a sprayer to spray the urea solution evenly on the front and back of the leaves.
- Cover the leaves thoroughly with the solution, but avoid excessive dripping or runoff.
- Choose early morning or evening, and avoid high temperatures or direct sunlight.
- After fertilizing, protect the plants from the rain, and do not water on top.
3. Benefits of Using Urea in The Fall
- Storage
When hydrangeas grow, they use a lot of nitrogen from the soil. So, there will be a shortage of nitrogen in the soil. Foliar urea application in the fall can reduce the dependence of hydrangea on soil nitrogen and reduce nitrogen runoff. At the same time, foliar spraying urea can increase the nitrogen content of hydrangea roots.
Leaves can quickly absorb most of the nitrogen, and the plant will transfer from the leaves and store the nitrogen. The stems and roots of hydrangea sprayed with urea had 47% higher nitrogen content than those without urea spray.
- Stems
Before hydrangea goes dormant in winter, nitrogen causes it to grow new stems and thicken old ones. Enough nitrogen stored will make hydrangea form a strong cell wall. So, the more nitrogen stored in a hydrangea plant, the better it can endure cold weather.
- Leaves
Using urea spray on hydrangea leaves during fall can help promote the growth of more and larger leaves in the next growing season, especially for bigleaf hydrangeas. Moreover, the content of chlorophyll in leaves will also increase.
- Flowers
Spraying urea on hydrangea leaves in the fall can increase the blooming size and fullness in the next year.
4. Combining with Other Fertilizers
In the fall, spraying urea on the hydrangea leaves can help the plants store more nitrogen. In addition to nitrogen (N), hydrangea needs other nutrients, such as phosphorus (P) and potassium (K). Hydrangea needs different nutrients at different growth stages.
- Cuttings
The primary way of hydrangea propagation is cuttings, and I usually do this task from May to July. One of the critical factors for the success of cuttings is to keep the soil moist.
I will use 10-52-10 (N-P-K) liquid fertilizer to promote root growth in cuttings. In the late growth stage of cuttings, using the same liquid fertilizer once a week can make the stem length of the cuttings thicker. When the cuttings are mature, I will use this liquid fertilizer again to promote the root growth of the cuttings.
- Growth period
Hydrangea likes moister and well-drained soil. So there can be no waterlogging in the soil, which can lead to mold infection.
When transplanting hydrangeas, I use a slow-release 15-9-11 fertilizer as a base applied to the soil. I use water-soluble fertilizer (18-11-18) and trace elements to ensure rich and balanced nutrition. Before hydrangea blooms, I will use fertilizers with high phosphorus content to help flowering and extend the blooming period.
- Late growth stage
I stop using water-soluble balanced fertilizers. I will use 4-19-35 (N-P-K) water-soluble fertilizer and trace elements to meet the nutritional needs of plants.
5. FAQ
Q: Is urea suitable for all plants?
A: How to use urea depends on the nutritional needs of plants, soil types, and environment. Generally, grass and some vegetables need a lot of nitrogen during their growth. Avoid using urea for some plants that are sensitive to high nitrogen. It can lead to over-nutrition or make the plants die.
Q: Can flowering plants use urea?
A: No plant can grow without nitrogen. Urea is a good source of nitrogen that can make the leaves healthier and improve roots' growth.
Whether urea is suitable for flowering plants depends on plant type, growth stage, and method of use. However, do not use too much urea fertilizer, which will hurt plants. Especially at the beginning, be sure to use a small amount.
If you plan to use urea in your garden, getting advice from an expert is a good idea. It's better to be safe than sorry.
Q: Will urea change the pH of the soil?
A: Urea will change the soil pH and make the soil acidic. So, to keep your soil healthy, it's essential to check soil pH regularly. You can use some soil modifiers to keep the soil healthy.
Q: What are the cons of urea fertilizer?
A：
- Volatile will cause the use effect not to be good and pollute the air.
- Excessive use of urea will increase plant diseases and pests.
- Using the wrong way can cause pollution in rivers and lakes.
- It only has nitrogen and nothing else that plants need to grow.
6. Conclusion
Nitrogen can make the hydrangea stem grow thicker and make the flowers fuller. Spraying urea before falling leaves can increase nitrogen storage and pave the way for growth and blooming in the next year.
Giving plants a steady and balanced supply of nutrients over a long period is vital to help them grow well. I do not recommend using urea frequently, as it can upset the balance of nutrients in the soil and harm the soil's health.
If you have any questions or opinions, please message me, and I wish you a pleasant gardening trip.
Bibliography:
- Bi, G., Scagel, C. F., & Harkess, R. (2008). Rate of Nitrogen Fertigation During Vegetative Growth and Spray Applications of Urea in the Fall Alters Growth and Flowering of Florists' Hydrangeas. HortScience horts, 43(2), 472-477. Retrieved Feb 18, 2024, from https://doi.org/10.21273/HORTSCI.43.2.472
- What is nutrient pollution? NOAA. https://oceanservice.noaa.gov/facts/nutpollution.html
- Bi, G., & Scagel, C. F. (2008). Nitrogen Uptake and Mobilization by Hydrangea Leaves from Foliar-sprayed Urea in Fall Depend on Plant Nitrogen Status. HortScience horts, 43(7), 2151-2154. Retrieved Feb 20, 2024, from https://doi.org/10.21273/HORTSCI.43.7.2151
- Bi, G., & Scagel, C. F. (2009). Effects of Fall Applications of Chemical Defoliants, Urea, and Gibberellic Acid on Defoliation in the Fall and Performance of Hydrangeas During Forcing. HortScience horts, 44(6), 1604-1607. Retrieved Feb 20, 2024, from https://doi.org/10.21273/HORTSCI.44.6.1604
- HERO ID 6980742, Reference Type Journal Article, Title Rate of nitrogen fertigation during vegetative growth and spray applications of urea in the fall alters growth and flowering of florists' hydrangeas, Author(s) Lenssen, AW; Sainju, UM; Jabro, JD; Bi, G; Scagel, CF; Harkess, R, Year 2008, Is Peer Reviewed? Yes, Journal HortScienceISSN: 0018-5345, Publisher AMER SOC HORTICULTURAL SCIENCE, Location ALEXANDRIA, Volume 43, Issue 2, Page Numbers 472-477, DOI 10.21273/HORTSCI.43.2.472, Web of Science Id WOS:000254026400037
My name is Arthur Mo. I am a gardener who loves gardening so much. I graduated from Ocean University of China. After I returned to Japan, I began to learn how to cultivate hydrangeas and daisies. Mr. Mitsuhiro (my master) taught me to sow, cut, fertilize, and manage diseases and pests. For nine years, I have been sharpening my planting skills. In 2022, my family and I moved to Florida. The warm climate of Florida gives me the impulse to continue cultivating hydrangeas and daisies. I began my gardening trip in my backyard and unswervingly contributed my efforts to these plants. I love these plants deeply, and at the same time, I also thank my family, my master, and friends for their understanding and support.