Tips for fertilizer
Plants grow best when conditions are ideal. Weather, water, and nutrients are all key to healthy plant growth. Applying fertilizer can help a plant grow more vigorously, be more resilient, and be better able to resist pests and disease.
In this article, we’ll cover some tips for fertilizing, helping you to make the most of the growing season.
To understand more about fertilizers themselves, check out these two articles from Lexi and Erin:
Understanding Fertilizer Labels
Let's dive in.
Water
Plants need water, but soil does too. When soil dries out, it can contract and crack, becoming less able to absorb water evenly. Water also moves nutrients through the soil; in dry soil, salts can quickly accumulate, which can damage roots and make soil less fertile.
When applying fertilizers, it's important to water before and after application. In addition to preparing the soil, watering beforehand also prepares the plant. The additional nutrients stimulate growth, which in turn increases the plant's water demand, so plants can become easily stressed if the soil is dry when fertilizer is applied.
Ensure the soil around your plants is evenly moist before applying fertilizer. Pay attention to any dry spots and spot water as needed. Then water after your fertilizer application to help the nutrients move into the root zone.
The exact amount of water will vary depending on what kind of fertilizer you are using. Many fertilizers will have specific instructions for use, and some liquid fertilizers will not need watering-in after application because they are a lower concentration compared to granular fertilizer.
Temperature
All plants have an ideal range of growing temperatures. Inside this range, plants are drawing up nutrients and water from the soil and transpiring through their stomata. Outside of this range, plants typically limit growth or stop growing entirely. Some of this growth pause is obvious — many plants go dormant in the winter, for example — while some plants in the heat look much the same, though in heat stress they redirect their energy toward water management rather than growth.
Many fertilizers also depend on microbial activity in the soil to break them down and increase absorption. While it can vary between fertilizers, for most types the ideal temperature range for application is 60°F to 75°F (15°C to 24°C). Applying outside this range, particularly in high heat, can cause fertilizer burn or simply waste the application since the plant isn't actively growing.
Perhaps the greatest exception to this rule is applying slow-release fertilizers in late winter or early spring when plants are still dormant. This allows the nutrients to be available and ready to be taken up as soon as growth resumes in spring.
Type
The four main categories of fertilizers are:
- Organic or synthetic
- Granular or liquid/water-soluble
Erin breaks down these categories in detail in her article here: Fertilizer: Beyond the Bag
Additionally, fertilizers are either slow-release or quick-release, and understanding which type you have will determine how and how often you apply it.
Slow-release fertilizers break down gradually over weeks or months, feeding plants consistently without frequent reapplication. They are a good choice for busy gardeners or for plants that benefit from a steady, low level of nutrients over a long period. Because they release nutrients slowly, the risk of over-fertilizing is lower, making them a forgiving option for beginners.
Quick-release fertilizers act faster and are useful when a plant needs an immediate nutrient boost — if it is showing signs of deficiency, for example, or during a period of rapid growth. However, they need more regular application and carry a higher risk of fertilizer burn if applied too heavily or to dry soil, which is why watering before application is particularly important when using them.
Check the label of your fertilizer to confirm whether it is slow- or quick-release, as this affects both the frequency of application and the watering requirements. When in doubt, less is more — over-fertilizing is more damaging to plants than under-fertilizing.
Timing
There are two aspects to timing. The first is the frequency of application — how often do you need to apply? The second is the time of year, or stage of the plant's life. Both are very important to consider when applying fertilizers.
Frequency
For heavy-feeding plants, regular application may be necessary. Just as regular watering helps to minimize stress, so does regular fertilizer application for plants that need it. The frequency will depend on the type of fertilizer you are using — slow-release fertilizers may only need applying once or twice a season, while quick-release fertilizers may need applying more frequently during the growing season.
Keep a simple fertilizing log — even just a note on your phone — so you can track when you last applied and avoid accidental over-application.
Time of Year
Plants have different nutrient needs at different times of year. During the active growing season — typically spring and summer — plants are drawing up nutrients readily and benefit most from regular feeding.
As days shorten in autumn and plants begin to prepare for dormancy, fertilizer should be applied less frequently and less heavily, giving plants time to harden off and prepare for winter. During full dormancy, fertilizing is generally unnecessary and can do more harm than good.
A good rule of thumb is to fertilize when you see active new growth, and to stop when growth slows. The plant will often tell you what it needs.
Growth Stage
The stage of a plant's growth also matters. Seedlings and young plants need a more diluted application (if any fertilizer at all) to avoid overwhelming their developing root systems — too much fertilizer too soon can cause root burn and set a young plant back significantly.
Established plants can handle regular feeding during their active growing season. Plants that are flowering or setting fruit may benefit from a fertilizer higher in phosphorus and potassium to support that stage of growth, while leafy plants and those grown primarily for foliage tend to respond well to higher nitrogen applications.
Always check the recommended dilution rate for seedlings on your fertilizer label — many manufacturers include separate guidance for young plants, and it's often significantly lower than the standard rate.
Wrapping Up
Fertilizing well is less about adding more and more about adding at the right time, in the right conditions, and in the right amount. With the tips here and the right fertilizer for your plants, you'll be giving them the best possible chance to grow and thrive.
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