seedlings not growing true leaves

Some seedlings not growing true leaves, stalled at cotyledons


This isn’t my first grow, but this is the first time I’ve started seedlings in rockwool, and the first time I’ve tried growing feminized genetics. All seeds were started the same way I’ve always successfully started seeds using the paper towel method and then directly into the rockwool cubes. The cubes were soaked in PH 5.8 water with a drop of superthrive and 0.5ml of hydroguard. Temps stay in the high 70s low 80s with a RH of 60-70%. Light is a 600w Viparspectra LED about 3 feet away. They are all about 5 days since sprout.

Here are all 6 seedlings:

As you can see, the first three rows are coming up very stunted. The AK and the MK both are showing no signs of developing true leaves, although the SuperSkunk on the left is starting to develop them.

Hey all! This isn't my first grow, but this is the first time I've started seedlings in rockwool, and the first time I've tried growing feminized genetics…

Why Does My Tomato Seedling Stop Growing with 2 Leaves?

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After tomato (Lycopersicon esculentum) seeds germinate the seedlings emerge from soil and have a pair of small leaves, called cotyledons; then about three weeks later each seedling should produce its first set of true leaves. If your seedlings stopped growing before that point, you probably haven’t given them suitable growing conditions. Tomato plants grow as perennials in U.S. Department of Agriculture plant hardiness zones 10 through 11 and as annuals elsewhere.

If your tomato seedlings are not growing true leaves, then they may not be receiving the light, food or water that it needs to thrive.

Light and Temperature

A tomato seedling that doesn’t get adequate light and warmth may end up leggy or stunted. A leggy seedling has a long, thin stem because it stretches toward the light. The young plant doesn’t have the energy to put out more leaves. Ideally, keep your seedling under a bright fluorescent light, such as a shop light, for about 16 hours per day.

Tomato seedling problems can also be caused by temperature variations. A tomato seedling grows best when the temperature is 65 to 72 degrees Fahrenheit. Very hot or cold temperatures are likely to damage the seedling and slow new growth.

Appropriate Use of Fertilizer

If you planted your seedling in a potting mix, it may contain enough nutrients to sustain the plant for a few weeks. If you used sterile seed-starting medium, such as peat or coconut coir, you might need to give the plant a bit of food. Feed the plant with 1 teaspoon of an all-purpose fertilizer, such as a 15-30-15 fertilizer, diluted in 1 gallon of water.

Two evenly spaced applications of fertilizer is usually enough before moving the plant outdoors to a garden. Avoid giving the seedling too much fertilizer. Overfeeding can make a seedling spindly from rapid growth. It also may cause it to stop growing.

Too Much Water

A tomato seedling needs water to grow, but too much water actually can stunt or kill the plant. Excess water sometimes causes fungal diseases, including a condition called “damping off.” A seedling with that problem flops over or rots at the base of its stem. The damage can’t be repaired. In order to help prevent it, allow the seedling’s soil to dry out slightly before watering again. The soil should feel moist, but not soggy, to your touch. Water with clean tap water instead of stored rainwater, which can harbor fungi and bacteria.

Plant Not Growing After Transplant

It’s generally safe to move a tomato seedling to a bigger container after the plant grows its first two true leaves. Those true leaves are not the cotyledons, which are the first two leaves the seedling had when it emerged from the soil. Transplanting a seedling before it has two true leaves can cause the plant to have stunted growth.

Before transplanting, gently lift the seedling out of its container, and check its root growth. Don’t transplant the seedling if its roots are very small. Because a seedling is delicate and easily damaged during transplanting, handle it by its cotyledons to avoid damaging the stem when you move the plant.

Why Does My Tomato Seedling Stop Growing with 2 Leaves?. Tomato plants (Lycopersicon esculentum) offer fruits that burst with rich flavor. Growing the plants from seeds, however, is much less expensive than buying them from a nursery. After the seeds germinate, the seedlings emerge from soil and have a pair of small …