Zinnias are popular annual flowers, celebrated for their vibrant colors and ease of growth. While these cheerful blooms can transform a garden, their rapid height often raises the question of physical support. Whether a zinnia requires staking depends on its genetic potential for height and the environmental conditions. Understanding which varieties are prone to flopping and when to intervene ensures your garden remains upright and colorful.
Determining When Support is Needed
The need for support is determined by the specific zinnia variety and its mature height. Dwarf types, such as the Profusion or Thumbelina series, typically grow only 6 to 18 inches tall and are self-supporting due to their compact, branching habit. Support is necessary for tall varieties, particularly cut-flower types like ‘Benary’s Giant’ or ‘State Fair,’ which can reach three to five feet. These towering plants develop thick but often hollow stems, making them structurally vulnerable as they mature.
The weight of large, fully double blooms also increases the likelihood of the stem bending or snapping. Environmental factors compound this issue, as tall zinnias are highly susceptible to strong winds and heavy rainfall. A strong gust can easily cause a fully grown plant to snap or lean permanently, especially if the soil is saturated. Staking is a preventative measure, generally becoming necessary for any variety expected to exceed 36 inches in height.
Practical Methods for Staking and Support
The most effective approach is to install support early, ideally when plants are young and about one-third of their expected mature size. Waiting until stems begin to lean makes correction difficult and risks causing damage. For a few plants, individual staking is straightforward, using bamboo or metal rods sunk close to the main stem, taking care not to injure the roots. Secure the stem to the stake using soft ties or twine in a figure-eight pattern, allowing for growth without girdling the plant.
When growing a large patch of zinnias, especially for cutting, a collective support system is more efficient. A corral or grid system involves placing sturdy stakes at the corners of the area and running horizontal lines of twine or wire between them. Specialized flower netting, such as Hortonova or pea netting, offers a discreet solution. This netting is stretched horizontally over the young plants, suspended 12 to 18 inches above the soil. As the zinnias grow upward through the grid, the netting supports the stems and heavy blooms, becoming nearly invisible once the plants fill in.
Cultivating Sturdy Zinnia Stems
Beyond external support, cultural practices encourage the development of naturally robust stems, lessening the reliance on staking.
Pinching
The technique of “pinching” is an effective method for strengthening a zinnia’s structure. Pinching involves removing the central growing tip when the plant is young, typically when it has reached six to twelve inches and developed two to four sets of true leaves. This action disrupts apical dominance, signaling the plant to divert energy into lateral buds and produce multiple side branches. The resulting plant is bushier, produces more flowers, and features a stronger, more branched stem structure better able to withstand wind and rain.
Spacing and Watering
Proper spacing also contributes significantly to stem strength by improving light exposure and air circulation. Tall zinnia varieties should be spaced 12 to 18 inches apart, while smaller types may require 9 to 12 inches. Adequate space prevents plants from stretching too quickly for light, which results in weak, spindly, or “leggy” growth. Watering practices should focus on encouraging a deep, strong root system to anchor the tall stems. This is achieved by providing deep, infrequent watering at the soil level, rather than light, overhead sprinkling. Overwatering can saturate the soil, weakening the root hold and making the plant prone to toppling.