No more blooms - Knowledgebase Question

Scottsdale, AZ
Question by Marjie177
September 4, 2007
My garden has lost all it's flowers! I have several Lantana, a Bougainvilla, a few air ferns and a Hibiscus in a planter about 1.5 ft wide and 20 feet long. I have tried the direct sun color spots and things like marigolds in my garden but they do not do well for more than a month. I get pretty heavy sun for about five hours midday and it seems to toast the lighter plants. The plants that are surviving are doing well but not blooming at all and I would really like to have some flowers out there, it is why I bought them. The Lantana and Hibiscus in my apartment community landscaping blooms all year long, what am I doing wrong? I had a hard time starting out the garden the soil as pretty bad and very rocky but I added compost and some potting soil down about a foot. I have also added a soaker hose through the planting bed for easy watering. I give the whole thing about 20 min every morning. Is that too much or too little? I also want to start some kind of vine along the retaining wall but am not sure which kind since it would have to grow quickly and survive the heat and sun. Any suggestions on how to brighten up my garden with a flowering vine and return the blooms to the exhisting plants would be helpful. Thanks!

Answer from NGA
September 4, 2007


There are a variety of issues that may come into play. Even plants with long flowering seasons will take breaks. Plants that like full sun, such as the bougainvillea and lantana, may not be getting enough. Full sun is generally 8 hours per day. Hibiscus, on the other hand, benefits from protection from the hottest part of the day, such as some filtered light. As for annuals like marigolds, if you happen to plant, say a cool season flower, just before the warm season begins, it won't last long. There are two distinct growing seasons in the low desert with different annuals thriving in each season. There's a cool season from approximately the end of September through April. Annuals can be installed from late September to February. Some gardeners prefer to wait until October, as cooler temperatures also help kill off whitefly populations which can quickly decimate plants. The warm season starts with planting in mid to late February. Some plants will make it through the summer's heat; others will end their growth when the heat arrives in May or June. As for whether that's enough water, I can't say. It depends on how much water the soaker hose puts out, soil conditions, weather, etc. Here's some basic info on watering plants in the desert that will help you determine whether your watering needs adjustment. As a general guideline, most landscape plants, such as you have, shouldn't need daily watering.

Running drip several times a day is not effective because the root ball doesn?t get moistened. For example, an emitter that puts out one gallon per hour would only put a quart of water on the ground in 15 minutes. For mature trees, water should soak 3 feet deep; for newly planted trees, about 2 to 2.5, depending on the size/depth of the rootball when it was planted. I've included some info on watering below:

Use a soil probe (any long, pointed piece of metal or wood to poke into the soil) to check how far water has penetrated. The probe moves easily through moist soil, but stops when it hits hard dry soil. There are numerous variables involved for watering schedules, such as type of soil, how fast or slow it drains, sun and wind exposure at your site, temperature, age and condition of the plants and much more. Use the information above to determine how moist the soil is before automatically applying more water. It's essential that you allow your drip system to run long enough for water to penetrate the appropriate depth. Depending on the size emitters, soil type, etc. this might take several or many hours.

Use the 1-2-3 Rule as an easy method to remember how much water to apply. Small plants with shallow root systems, such as perennials, veggies, herbs, cacti, succulents have roots that reach about 1 foot deep, so water needs to penetrate that far. When the top 1 inch of soil dries out, it's usually time to water again. Shrubs have root systems that are 2 feet deep so water needs to soak 2 feet deep. When the top 2 inches of soil dries out, it's time to water. Trees are 3 feet deep. As plants establish root systems, the time between waterings can be lengthened, but it is always essential to water to the same depth. So you are applying the same amount of water with each irrigation regardless of the time of year, but the frequency changes. As warm weather arrives, you need to water more frequently than during winter.

Desert soil and water both contain salts, which can accumulate in the root zone over time. This salt buildup forms where the water stops penetrating. Short periods of watering cause salts to build up in the top layers of soil and damage or kill your plant. Salt burn shows up as yellowing, browning along leaf edges, and leaf drop. Deep watering?or leaching?prevents this by flushing the salts past the root zone. Always water slowly, deeply and as infrequently as possible.

Here are some desert-adapted vines:

Pink trumpet vine (Podranea ricasoliana) blooms in summer and fall. Needs significant support.

Cat's claw vine (Macfadyena unguis-cati) blooms in spring (yellow)

Lady Bank's Rose (Rosa banksiae) blooms in spring (white or creamy yellow depending on variety.) There's an absolutely enormous one in bloom right now at Boyce Thompson hanging above the herb garden. I'm sure there are others closer to home, but if you get out there, take a look.

Queen's Wreath (Antigonon leptopus) blooms summer and fall (coralish-reddish sprays). Frost sensitive but comes back.

Yellow Morning Glory (Merremia aurea) blooms spring (yellow)

Passionvine (Passiflora spp.) Food for larval stage of butterflies.

Hardenbergia. blooms in February/March with narrow purple clusters, somewhat lilac-like.

Snail vine (Vigna caracalla). blooms in spring/summer with lavender flowers. Frost sensitive, but comes back.

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