Feeding Plants for Different Stages of Growth
Getting the nutritional needs of your plants right is one of the key features of successful plant cultivation. But “right” can feel like a moving target sometimes. Here’s what you need to know about feeding your plants for different growth stages.
As tricky as providing the right nutrition for soil-based plants can be, the process is more challenging with a hydroponic garden. A hydroponic set-up is a simulated environment where nutrient recipes have to be water-soluble, complete and stable. In other words, almost everything hydroponic plants need to flourish has to be provided artificially in a water-soluble form.
Plants need different nutrients at different stages of growth. They may also have special requirements depending on the nature of their native soils or the demands of their unique features and characteristics.
This might sound complicated, but most nutrient manufacturers have done the hard work for you by developing complete products that address the general needs of most plants.
They also sell special formulas optimized for different stages of growth and to meet the unique needs of specific types of plants, like tomatoes or orchids, for instance. These formulas can include enhancements that encourage specific desirable characteristics like improved flavor, better color or a stronger scent.
Hydroponic nutrient formulas are proprietary, but the recipes conform to our general understanding of when, how and how much of a particular nutrient a plant will need as it matures. For example, let’s look at the macronutrients nitrogen and phosphorus.
Plants require both of these nutrients to perform essential functions throughout their lives. They’re always important, but during leaf development, nitrogen demand increases dramatically, and phosphorus is particularly useful during bud growth, flowering and seed development. The optimal ratios vary.
You’ll see this on soil fertilizers, where the first two numbers on the front of the bag will change depending on their nitrogen and phosphorus content by weight. Plants also use these macronutrients in combination.
Among its many roles, phosphorus helps plant roots absorb nitrogen more effectively. This kind of interdependence isn’t uncommon, and isn’t limited to the plant world, either. In the human body, vitamin D and magnesium aid in calcium absorption and retention.
Understanding the Different Types of Plant Nutrients
Scientists have identified the most important nutrients in plant cultivation and have placed them into three broad categories: macronutrients, secondary nutrients and micronutrients. The distinction refers to the quantity rather than the importance of any specific nutrient.
As an example, plants use large amounts of nitrogen (a macronutrient) for most of their basic functions, but only need trace amounts of copper (a micronutrient). Both nitrogen and copper are important in photosynthesis.
The following is a list of nutrients you’ll find in hydroponic preparations. Pay attention to the letter designations for each. Nutrients will often be referred to on product labels and in scholarly publications by these initials, which are their identifiers on the periodic table.
- Nitrogen (N)
- Phosphorus (P)
- Potassium (K)
- Magnesium (Mg)
- Sulfur (S)
- Calcium (Ca)
- Boron (B)
- Chlorine (Cl)
- Manganese (Mn)
- Iron (Fe)
- Nickel (Ni)
- Copper (Cu)
- Zinc (Zn)
- Molybdenum (Mo)
While most soil-based fertilizers provide only macronutrients, hydroponic fertilizers contain all three categories of nutrients, although micronutrients are needed in very small quantities measured in parts per million (ppm). Missing from the list above are three essential nutrients plants extract from air and water: hydrogen (H), carbon (C) and oxygen (O).
When to Feed Your Plants
Plants are pretty active, even when they look static. The nutrients necessary to sustain them through huge changes in function overlap, but the demands for specific mineral concentrations shift to a greater or lesser degree during:
- Initial growth and root development (young seedlings)
- Vegetative growth (major leaf and root development)
- Budding, blooming and ripening
Nutrient formulations focus on these key nutrient uptake changes as plants transition from one major stage of development to the next. In fact, hydroponic nutrients are often sold as multi-step powders or concentrated liquids designed to coincide with the shifting needs of growing plants. When sold this way, they are intended to work in a series, not all at once.
There’s a good reason for this separation. Combining some ingredients can limit their effectiveness in water-soluble form. If incompatible minerals are among the ingredients used in a particular nutrient series, they’re designed to be applied in separate steps.
Factors to Consider When it Comes to Plant Nutrition
External factors play a role in the way nutrient blends perform, too. Concentrations of a particular dissolved mineral may increase, sometimes dangerously, when used with local water resources that already contain high levels of that mineral.
It’s a good idea to contact your municipal water utility for information about the water in your area, or consider having your water tested if you plan to use well water to feed your plants.
They can become too concentrated if they aren’t adjusted and managed over time. Crops that grow quickly may also use nutrients and water more rapidly than expected. It’s important to follow the recommendations for use of a particular product, and observe the results closely.
There are a number of variables to consider. Crop type, ambient temperature, water pH, light intensity and CO2 levels are all factors that can impact the way products perform.
These are some of the reasons why experienced indoor gardeners sometimes like to develop their own nutrient recipes using readily available ingredients like calcium nitrate, magnesium sulphate (heptahydrate) and potassium nitrate.
Boost the Performance of Your Plant Nutrients
The right blend of nutrients is at the core of any effective hydroponic fertilizer product, but there are a few other ingredients to keep in mind, especially when you’re working to achieve specific growing goals like early flowering or rapid leaf development.
Plants can make use of helpers to perform certain functions such as absorbing nutrients more easily or using them more efficiently. Hydroponic nutrient manufacturers include these helpers in their products as boosters and enhancers.
The formulas for specific products are protected, but beyond using basic nutrients like phosphorus and potassium to stimulate flower production, they might include vitamins like B1 to help plants sustain the energy necessary for growth spurts, or make it easier for them to combat the destructive effects of stress.
Formulations may also contain enzymes that enhance root uptake, the vegetative equivalent of cutting a steak into manageable bites that are easier to chew. Some additives stimulate root growth early, or enhance root efficiency through the introduction of beneficial bacteria. Others encourage rapid and profuse bud development.
Many nutrient products on the market use ingredients like vitamins, enzymes and boosters to help plants grow faster and larger, or produce sweeter fruits or more abundant flowers. They augment the work of what constitutes the backbone of any hydroponic growing strategy, core nutrients and the environmental conditions necessary to enable plants to fully exploit them.
Written by Sara Elliott | Gardener, Writer