Growth Phase: Guide for Outdoor Growers
Do you want to grow strong, healthy plants in your garden this year and harvest a solid yield? You need to start already during the vegetative phase – the period when plants build roots, leaves and stems that will later form the basis of your harvest. In our guide we’ll advise you how to support vegetative growth in outdoor cultivation.
During their life cycle plants go through two specific periods – the vegetative (growth) phase, when they grow and form leaves, roots and stems, and the generative (flowering) phase, when they bloom and produce seeds. The length of the vegetative and generative phases varies between species: some have a long vegetative phase and short flowering (e.g. trees), others quickly switch to the generative phase (e.g. annuals), and for some plants (e.g. perennials) these phases repeat cyclically over several years.
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Why healthy stems and roots are important
During the growth phase it is crucial for plants to develop enough roots, leaves and stems, because during flowering they will devote most of their energy to producing flowers, fruits and seeds. Simply put, without strong stems and healthy leaves and roots you won’t get a proper harvest. Stems support leaves, flowers and fruits and contain the vascular system that transports water and nutrients throughout the plant. The root system also serves multiple functions: roots take up nutrients and water from the substrate and act as a reserve during dry periods. In addition, deep and well-branched roots ensure plants can withstand strong winds, which is important for outdoor growing.
Sufficient nitrogen
Just like with people, a proper diet is half the battle for plants. Throughout their lives plants need a total of 17 different nutrient elements. Some they obtain from the air and water (carbon, oxygen, hydrogen), but most are taken up from the soil by the roots. If any of these essential nutrients are lacking, it will have a significant impact on their health. Fertile soil and the right fertilizers are therefore the first step to keeping your plants in good shape during the vegetative phase so they quickly develop robust stems and many roots. 
The three most important nutrients in the soil for plants are nitrogen (N), phosphorus (P) and potassium (K), which they consume in the largest amounts. During the vegetative phase nitrogen in particular plays a key role — it is the cornerstone for producing proteins, which are the “building blocks” for all plant cells and tissues. Without proteins plants couldn’t form new leaves, stems or roots. Nitrogen is also a component of chlorophyll, the green pigment that enables photosynthesis — the conversion of light into energy. Finally, nitrogen is part of RNA and DNA and various enzymes. Nitrogen gets into the soil by several routes:
Biological nitrogen fixation: Some bacteria (e.g. Rhizobium or Azotobacter) convert atmospheric nitrogen (N₂) into ammonia (NH₃). These bacteria live both in the soil and on the roots of leguminous plants (peas, beans, clover). Planting these species in beds (green manuring) is a great natural way to increase nitrogen levels in the soil.
Organic matter: Nitrogen also enters the soil as part of decomposing organic matter, which soil microorganisms convert into nitrates (NO₃⁻). The most effective way to add organic matter to the soil is compost, humus and mulching.
Growth fertilizers: There is a vast range of fertilizers, from fully organic to purely mineral, with slow or fast effects, in powder or liquid form. The right choice depends mainly on your cultivation method. While liquid fertilizers with fast action are suitable for growing in pots, organic slow-release variants are better for soil. Whatever you choose, a growth fertilizer should always contain a high proportion of nitrogen (N).
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Supporting nutrients
Calcium (Ca) and silicon (Si) are two nutrients that most outdoor growers don’t pay much attention to because they are usually sufficiently present in the soil. Still, a deficiency of silicon or calcium during the growth phase can have a major impact, since both elements directly affect the strength of cell walls. When a plant receives enough silicon and calcium it has stronger leaves and stems and better resists wind, drought and pathogens.
Calcium: This element is essential for the development of new cells and also regulates the transport of water and nutrients between cells. Calcium deficiency in plants shows as deformed or dying young leaves and slowed growth. A good source of calcium for outdoor cultivation is dolomitic limestone, which also helps reduce soil acidity. A quick source of calcium for plants in the growth phase are liquid fertilizers containing calcium and magnesium (CalMag). Calcium is also present in decomposing organic matter such as compost or mulch.
Silicon: In outdoor cultivation in open soil silicon is widely available to plants, but if you grow in coco or inert substrates your plants may lack it. Silicon increases the strength of cell walls so plants better withstand high temperatures, dry air and drought. If you want to provide silicon quickly and protect plants against hot weather, try silicon as a foliar application, for example Terra Aquatica Silicate.
Watering and soil moisture
The vegetative phase is a period of rapid, intensive growth and plants need a regular supply of water. Especially young plants with developing roots can be severely slowed by drought. On the other hand, overwatering the substrate can lead to root rot and the development of molds. Therefore, when watering outdoor plants it is good to follow these rules:
- Water more often but in smaller amounts rather than all at once.
- Check soil moisture regularly – it should feel damp to the touch but not waterlogged.
- Water in the morning or evening.
- During periods of heavy rain ensure sufficient soil drainage.
For more useful tips and guides for outdoor and indoor growers visit our Higarden blog!