Avocados will grow in our area, but watch out for cold temperatures

Garden columnist Dan Gill answers readers’ questions each week. To send a question, email Gill at gnogardening@agcenter.lsu.edu. 

How does one grow avocado trees in Orleans Parish? If an avocado tree is grown from a seed, will it produce fruit? Does one need two trees for cross-pollination? Thank you. P. Bernard.

Growing avocados is not hard, but they are prone to freeze damage if temperatures get down to the low 20s, and they may be killed by temperatures in the teens. So severe winter freezes are the major issue when growing avocado trees.

Plant the trees in the ground in a sunny, well-drained area and hope for mild winters. Despite the issues with cold hardiness, avocado trees do produce fruit in southeast Louisiana in hardiness zone 9.

There are generally enough years between these catastrophic occasional freezes to get production, particularly in the south shore New Orleans area.

People often start avocado trees from pits, or you can purchase grafted named varieties at the nursery. The trees started from seeds can and do produce fruit. Grafted trees will produce fruit sooner and generally of better quality than seed-grown types.

Also, the avocado varieties offered at nurseries have generally been chosen to sell because they are among the more cold-tolerant types.

As to whether you need more than one tree to ensure production, avocado trees produce flowers with both male and female parts, but the stamens (male parts) and pistils (female parts) tend to mature at different times, preventing self-pollination. So, production is more reliable when more than one tree is planted (or if there are other avocado trees growing in your neighborhood), or when a self-pollinating, grafted named variety is planted.

I think I have a brown fungus on the leaves of some white caladiums I recently planted. There are brown splotches on the leaves between the veins. I have pink and red ones and they do not have this, and they all are planted in the same garden. Thank you, Don.

Disease problems are uncommon for caladiums. That helps make caladiums one of the most reliable plants for areas of our landscape that receive some shade.

The issue with your white caladiums is sunburn, a common problem when caladiums are planted in too much sun or plants grown in shady greenhouses are planted into sunny flowerbeds.

Sunburn causes tan patches on the leaves between the veins. Eventually, the tissue can burn through, and holes will even form.

In your situation, the caladiums were grown in shady conditions by the grower and the retail nursery where you purchased them. The spot where you planted the white caladiums gets more sun than they were accustomed to — so the leaves burned.

This does not necessarily mean there is too much sun in that location for them to do well. It is possible that the new leaves that grow out in this location will adapt to the sun and not burn — and all will be well.

But, if time goes by and the plants send out new growth and the new leaves also burn, you need to move the white caladiums to a shadier location. The pink and red caladiums are better adapted to the sun they are receiving, so they are not burning.

Caladium varieties vary on how much sun they can tolerate. Some will even grow in locations with full sun.

I have beautiful, large, green tomatoes on my bushes, but they will not ripen. It’s driving me crazy, and I’m sure I must be doing something wrong. How can I get my tomatoes to turn red? Chris

The old saying “a watched pot never boils,” comes to mind. When we focus on something intently while we wait for it to happen, it seems to take forever. And nothing seems to take longer than seeing those first green tomatoes finally turn red.

It takes six to eight weeks from the time of pollination until tomatoes reach maturity. This is not a problem. It is just a matter of patience.

Garden tips

LURE BUTTERFLIES: Pentas, lantana, verbena, zinnia, salvia (many different species and cultivars), milkweed and buddleia are excellent flowering plants to attract butterflies into your garden. These plants also provide colorful flowers through the summer. Do not use insecticides (even organic) on plants grown for butterflies.

MAY VEGGIES: Vegetables planted in May must be able to take the extreme heat of summer. Those that can be planted this month include amaranth (a great leafy green for summer gardens), cantaloupe, cucuzza, cushaw, eggplant (especially the narrow Japanese types), Malabar spinach, edamame (edible soybean), peanuts, pumpkin, Southern peas, hot peppers and sweet peppers other than bell peppers, luffa gourd, mirliton, okra, heat tolerant tomatoes, sweet potato, watermelon and yardlong beans.

HEAT IS HERE: May is a transitional month for Louisiana gardeners. Intense heat arrives in May with daytime highs reaching the 90s and nighttime lows staying in the 70s. Although the ideal season for planting hardy trees and shrubs is past, many heat-tolerant vegetables, bedding plants, summer bulbs and tropicals can be planted now.

WATCH THE WATER: As the weather heats up, monitor rainfall in your garden carefully (use a rain gauge) and water deeply, thoroughly and occasionally if the weather is dry.

TLC FOR TERRA-COTTA: Terra-cotta pots are beautiful, but as time goes by water evaporating from the sides and rim can leave behind unattractive mineral salt residues. Remove these by soaking empty pots overnight in a solution of one part vinegar to four parts water. The residue should come off with a stiff brush. If the pot is too large to soak, scrub it with the vinegar solution.