Nellie R. Stevens

The Nellie R. Stevens holly is an excellent choice when looking for a shrub for privacy screens that grows to a decent height.

DEAR NEIL: How often should I be watering new red oak trees I planted from 20-gallon pots last March over this dry winter? Maybe by the time this runs in the paper it will have rained, but for general purposes, how often?

Dear Reader: There are several variables that also enter the picture. Temperature is a big one, of course. Plants dry out much more quickly if it’s 70 or 75 degrees than if it’s cooler. And soil type, wind and plant size at planting (which you did not identify) all matter.

In general terms, if it’s been a week since last you soaked a new plant, you could water it deeply without fear of overwatering it. It’s better to keep it a bit too moist (but not wet) than it is to let it get a little too dry, especially if cold weather is about to arrive.

DEAR NEIL: What is the best fast-growing, tall screening shrub? We have a new shopping center behind us and I need privacy quickly.

Dear Reader: That’s a difficult challenge, because fast growth often translates into a plant that can get out of control quickly. At all costs, avoid Japanese ligustrum and golden bamboo. (Both are horribly invasive.)

Do not use redtip photinias. (It is highly prone to a fatal disease.) Waxleaf ligustrum is good in the southern two-thirds of the state, and it does not produce viable seeds.

However, my go-to tall privacy screen is Nellie R. Stevens holly. It grows to 12 to 15 feet tall and 8 or 9 feet wide with very infrequent trimming. It actually can grow even larger in Southeast and East Texas.

If that’s too large, step down to Willowleaf holly, which peaks out at 10 to 12 feet tall and 8 or 9 feet wide. These are evergreen shrubs that also produce large red fruit that persist all winter. They’re suited to sun or shade and all kinds of soils.

To speed up your privacy, buy larger plants initially. Set them out two-thirds as far apart as you’re going to allow the plants to grow tall. As example, if you’re growing Nellie R. Stevens hollies 12 feet tall, plant them 8 feet apart.

Water all new ligustrums and hollies by hand for their first two years. Water every three days during the warm months, and soak them deeply without fail. They do not wilt when they are beginning to dry.

DEAR NEIL: I like to raise my greenhouse plants in clay pots, but I frequently have green scum on the rims and outsides of the pots, also across the top of the potting soil. How can I get rid of that?

Dear Reader: That’s an algal scum that suggests that you’re overwatering your plants. Cut back either on the amount, or more likely the frequency with which you’re watering the plants.

It’s best to water deeply, then to let the top of the soil dry ever so slightly before you water again. However, the algal growth will remain dormant there, so you also need to remove it.

I usually take the opportunity to repot those plants. I’ll carefully tap them out of their old pots and set the pots aside. I’ll use a table fork to “comb” all the scum and top quarter-inch of potting soil off the top of the root ball.

I reset the plants into new, clean pots filled with fresh potting soil, carefully putting a thin layer of new soil across the top. From that point on I’m more careful in my watering.

Then I place the old pots into a washtub filled with water and 10 percent chlorine bleach and let them soak for a day or so. I pour out the bleach into a drain, flooding it with copious amounts of water, and I let the clean pots dry.

DEAR NEIL: We live in the Texas Hill Country, and I’m wondering what is doing this to our century plants. Stags rubbing their horns? Wild pigs? Any ideas?

Dear Reader: Great question, and I spent half an hour researching my reply. Deer would be a possibility as they rub the velvet off their antlers.

And the other thing that was mentioned commonly was agave snout weevils. These insects bore into the bases of the leaves of large species of agaves, most notably Agave americana (century plants) and lay their eggs. They do fatal damage to the crowns of the plants.

A couple of your photos looked somewhat similar to the snout weevil damage, so I at least wanted to introduce that possibility to you so you could do a little online research and exploring.

DEAR NEIL: I would like to grow some of my own annual flowers from seed. How difficult would it be to grow marigolds, zinnias, begonias and periwinkles?

Dear Reader: If you’re talking about starting them in greenhouse-like conditions, all except the begonias are definitely possible. But you’ll need fairly cool (65-70 degrees) conditions and full sunlight. Start marigolds and zinnias seven or eight weeks before you intend to plant them into the garden (no earlier than your frost-free date for your area).

Periwinkles would need really warm temperatures, so their seeds shouldn’t be planted until probably late March at the earliest.

Sow your seeds onto a screened, lightweight, sterile seeding mix. I prefer to sow in rows to make transplanting easier, and I only plant one type of flower in a given container. Use a fine spray to water the seeds into the top surface of the planting mix and cover it almost completely with glass or clear plastic.

Leave a narrow opening to allow excess moisture and heat to escape. Put it in a sunny location and keep a close eye on it to be sure the covering doesn’t fog up with condensation.

Transplant the seedlings when they’re large enough to handle by their first sets of true leaves, then pot them into 3-inch pots filled with lightweight potting soil.

Wax begonia seeds are extremely tiny. You can certainly start your own plants from seed, but it’s a much more challenging task. Do your homework ahead of time to learn how. Start begonia seeds sometime soon. They take several months to reach sizes suitable for planting outdoors.

It’s much more difficult to sow seeds directly into the garden. In the off-chance that that might be what you were asking, only zinnias and marigolds are really candidates at all. In those cases you’d need to wait until mid-April. Transplants are a much better idea.

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Have a question you’d like Neil to consider? Email him at mailbag@sperrygardens.com. Neil regrets that he cannot reply to questions individually.

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