Bedding Plants Yellowing and Dying

Q. My newly installed Penta bedding plants are dying, and
the leaves are turning yellow. They are getting plenty of water. Any ideas what
is causing them to die so fast?

Pentas, sometimes called Star Clusters, are summer
annuals grown as bedding plants for their color. The same as any other bedding
plants, they don’t like unamended desert soils, bad quality landscape soils or
desert landscapes. They abhor rock but grow best in soil amended with good
quality compost each time they are planted.

Penta bedding plants are from hot, tropical Africa so they like the heat, must be planted in soils with good drainage and fertilized every six weeks because they love rich soils. They don’t grow well in cool or cold desert soils or planted without a good soil amendment. In fact, they suffer badly when temperatures dip to 40° F in the spring or fall so plant them only when you are confident temperatures are warm and getting hotter.

            My guess
is the soil used for growing the Pentas was poor quality to begin with or a
poor quality soil amendment was added to it. If a poor quality soil or
amendment was used, water drainage will cause root rot which will cause
yellowing of the plants. If they were planted in February or March, they might
have been damaged by cool or cold weather which can also cause yellowing.

            

Soil Pro is a bagged very rich compost available from viragrow in North Las Vegas. If the soil is amended with this compost no fertilizer will be needed for the planting season.

            Add
enough good quality compost or soil amendment so that the soil is dark brown,
and you can dig in the soil with a garden trowel easily. While amending soil
for planting, throw in some 16 – 20 – 0 or comparable organic fertilizers to
get their roots off to a good start and the plants established quickly.

            Irrigate
bedding plants like vegetable transplants; daily after they are established and
twice a day during the two weeks of establishment. If this is a permanent bed
for bedding plants, use half inch drip tubing about 12 inches apart for
watering rather than the skinny laser tubing which tends to plug. Water with
drip irrigation anytime. When using overhead sprinkler irrigation, water
between 3 and 5 AM to minimize disease problems and water loss due to wind.

            If you
use a rich, high quality compost then additional fertilizer won’t be needed for
the first couple of months. After that, lightly fertilize bedding plants
monthly with a high nitrogen fertilizer such as ammonium sulfate or blood meal.
If a good compost is used as a soil amendment, then there are lots of nutrients
in the soil already.