Adventurous gardener tackles hydrangeas

The South Valley Rose Society will have its annual rose pruning demonstration in the Healing Garden at St. Rose Dominican Hospital, Siena Campus, Saturday from 10 a.m. to 2 p.m. If you missed the Las Vegas Valley Rose Society’s demonstration in the north part of the valley, then you can still catch this one at South Eastern Avenue and St. Rose Parkway in Henderson. This is a great climate for roses and this is your chance to ask the experts all your rose questions.

Also on Saturday I will be teaching how to prune pomegranates and persimmons at the University of Nevada Cooperative Extension Master Gardener Orchard in North Las Vegas starting at 9 a.m. and ending at noon. For directions or questions, contact me at

Q: I have a tricolored hydrangea bush in a pot in the front of my house. When is the right time to cut it back and how do I do it? After almost 20 years I finally got beautiful flowers on it last spring. After looking it up on the Internet, I think I’ve been cutting it wrong. I’d like your thoughts on this.

A: Wow. You are adventurous. Hydrangea is certainly not a desert plant. It does not like a lot of heat, low humidity or intense sunlight. It does like filtered light or early morning light and humidity. Just what people would tell you not to grow here. Go for it!

If you have evaporating water somewhere with no wind, it should like the spot, if it’s not too sunny. It does not like wind. You need a balance in the amount of light. Not enough light and the plant will not bloom. Too much light and it might cause leaf scorching, dieback or death.

It also is interesting because in many hydrangeas the flower color may change depending on soil acidity. It is assumed it is because of the availability of aluminum. If there is ever a plant that will test your ability as a gardener, this should be tops on the list. It is probably a wise decision to plant it in a container.

Tricolor refers to the color of the leaves, not the flowers. The leaves are supposed to be a combination of green, light green and a creamy color. This plant has been mislabeled in the past; whenever you see a tender plant with leaf colors like this, it is nearly always one that you must keep out of direct sunlight during the heat.

My understanding is that oak leaf and tricolor hydrangeas are pruned the same way. My understanding is that tricolor blooms on older wood, not this past year’s wood. This means that when you prune you will want to keep your older wood established and remove anything that is getting too old or may be crossing or too close to other productive stems.

The idea is to maintain older wood and selectively remove wood that is too old while constantly renewing the older wood. This also will mean you will have to remove excess new growth that makes the plant too dense and thick while, at the same time, keeping new growth that you want to preserve for future flowers. It’s not an easy task and certainly one that is difficult to explain. I hope this helps.

Q: In your Jan. 5 article on fruit trees, pruning and fertilizing trees, would this information also pertain to citrus trees?

A: Citrus usually does not require a lot of pruning. You will want to remove crossing limbs, along with limbs or stems that are broken or weak and thin if it is too dense to admit more light inside the canopy.

I might add you want to get your pruning done as soon as possible before flowering starts. If it has already started blooming, then you can still go ahead and prune unless it is full of blooms. Then I would wait. But my guess would be they have not started yet or it is a slow trickle of flowers right now. If you still have fruit and it is ripe, harvest it and then prune.

Q: My wife and I are building a raised garden for vegetables. It will be about 6-feet-by-9-feet and just under 3 inches deep and will be made of landscape bricks. What type of liner would be best along the inner walls to avoid weeping of irrigation on the stones? What type of soil can I have delivered to our site that is best for this purpose?

A: Congratulations on your move toward vegetable gardening in raised beds. I think your best alternative for lining your raised bed would be to use rubberized pond liners. They can be purchased in 5-foot-wide strips and in various lengths. These should be puncture resistant.

I would recommend getting a heavy-duty liner perhaps around 45 mil, not the 20-mil types. You can find sources on the Internet by searching for pond liners. It would be nice if it were also ultraviolet resistant.

Make sure you have drainage on the bottom of your raised bed; it should stick up slightly above your soil level and be wider than your wall so that a few inches of it also lies on the ground. These should last at least 10 years or more.

These liners will not add the toxicity to your soil that you might get by painting the inside walls with sealant. Make sure the strips overlap each other when lining the inside walls.

In my opinion, there is not a decent soil “manufactured” in the valley that can be used for vegetable growing and will get fabulous results. These types of soils can be developed over time, usually two to three years of growing plants and adding compost at planting time. This does not mean you will not be able to grow any vegetables; it just means you will see gradual improvement in the quality of the vegetables over time when combined with your efforts.

Whatever you do, do not use reject sand or even add it to an existing soil. This would be a big risk if you use it and just might result in a soil that will not grow anything decently. If it were me, I would use an existing soil at the site or, if purchased, a soil that drains freely.

Amend it with compost in a mixture of at least a 50-50 ratio compost to soil. Good compost is hard to find and it takes a lot of time and effort to make. So it will not be cheap! When evaluating whether you have good compost or not, use all of your senses; look at it, smell it and feel it. It should be dark brown, smell like a forest floor with no off smells like ammonia or manure and a fine texture, not coarse.

Even using the best compost will not give you fabulous vegetables or herbs the first year. It will take about three years for any desert soil, or one manufactured from desert soils, to reach its full potential for vegetable production. Be patient.

You should screen the soil and remove rocks that are larger than a golf ball. If you are growing root crops and asparagus, then you should remove the rocks even smaller than that to a depth of 12 inches. Amend it heavily with compost for the next two to three seasons at each planting and grow something the best you can. Even the first year your vegetables will be better than what you can get at the store; but in two to three years you can have superb vegetables in our desert climate and desert soils.

Bob Morris is a horticulture expert living in Las Vegas. Visit his blog at

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