Avoid overpruning Feathery Cassia
Some of the questions I fielded this week involved improper pruning, vines, radishes, thick-walled grapefruit and shady grass. Here are my responses.
Question: What is the yellow blooming shrub I see around town?
Answer: It is feathery cassia, or senna. It's an early bloomer covering itself with fragrant yellow flowers to show off through the spring. It never overpowers the landscape with its feathery foliage but becomes an airy attraction even when not in bloom.
Senna is one of the most abused plants in our landscapes. Unprofessional gardeners shear it into geometric shapes in the winter. This removes the flowering wood so all you get is a fuzzy bush and maybe some flowers. These untrained gardeners also do the same to other plants such as Texas Rangers. Both shrubs bloom profusely when pruned right.
When untrained gardeners shear plants, they remove the dominant buds. This activates the dormant buds at the base of each leaf below them and they want to become the dominant bud. This causes excess growth, which leads to smaller leaves that can't produce enough energy to generate blooms, and shrub decline sets in. The excess top foliage also shades the plant's base so foliage can't grow on the lower branches, and you end up with exposed stumps.
When pruned properly, these plants become lush and covered with blooms.
Q: Can you tell me about the lilac vine (Hardenbergia violacea) I fell in love with it at the Spring Preserve?
A: It is a beautiful spring blooming vine that loves our climate. This prolific flowering vine produces intense, bright-purplish pea-type flowers in dangling clusters. Beneath the flowers, dark-green, narrow, pointed leaves about 4 inches long covering the vine. The vine starts out slowly but gains momentum as its roots sink deep into the soil to become a fast grower. It will cover patios, walls and gazebos in shorter order.
Q: Why are my radishes all tops and tiny radishes?
A: All tops is a sign of too much fertilizer or overwatering. If radishes are small, it suggests you didn't thin them out. It could also signal a need for more phosphorous.
Q: Is it too late to prune Thompson seedless grapes?
A: Prune them before they leaf out, but do it earlier next year. They will bleed some but soon stop. If you don't prune grapes yearly, the plants become cumbersome and hard to control.
Q: Why is my grapefruit producing small fruit and thicker rinds?
A: Small fruit signals that the plant isn't getting enough water to its feeder roots. Water citrus out beyond the tree's drip line.
Too much nitrogen causes thick rinds and smaller fruit. Citrus doesn't need much fertilizer, so don't fertilize it this year.
Q: We want to plant a lime tree and want to know more about it?
A: First, limes and other citrus are sensitive to frost, so protect them on those frosty nights.
Limes take about five years to produce. In the meantime, you'll get some fruit but most of the flowers will abort. As it comes into production, it flowers in the spring and six to nine months later depending on the variety.
Q: Will zoysia grass grow in Las Vegas?
A: Yes, but it's slow to cover the area if you plant plugs. It can be invasive, so put a border around, and it goes dormant in the winter.
Zoysia grass handles foot traffic well, but if it breaks down, it's slow to repair. It will grow under shady conditions and conserves water.
If you want zoysia, you will have to order it.
Q: Why are the fronds on my recently planted date palm sagging and browning?
A: It's most likely suffering transplant shock because palms are slow to initiate roots in cold soils. It's also not getting enough water or nutrients because of the lack of root activity.
This is why we suggest planting palms after it warms up. Let's hope you see new growth as the weather warms.
GROWING TOMATOES
It's time to plant tomatoes. I'm giving an in-depth seminar on tomatoes at 8:30 a.m. every Saturday during March at the Springs Preserve, 333 S. Valley View Blvd. I'll show you how to conquer its many challenges. In years past, these seminars filled up fast, so get there early. The class is also taught at 8:30 a.m. on Sundays.
Linn Mills' garden column appears
on Sundays. He can be reached at
linn.mills@springspreserve.org
or 822-7754.
