Wednesday | October 18, 2017
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When broccoli bolts

Hi, need help! My broccoli plant started off pretty good. The round cluster was about an inch tall. Then it started growing tall and not looking anything like a broccoli. My lettuce does that also. Is it because I am growing them in large pots and not in the ground? — Lori

It’s hard to say for sure, but it sounds like the plants are bolting.

Bolting is the process of premature flower formation in response to high temperatures, as well as drought and starvation. This unwelcome occurrence in leafy plants such as broccoli, cabbage, lettuce, and spinach, takes the plant out of its leaf producing mode and switches over to flower and seed production.

Many vegetables are divided into two groups: cool season and warm season vegetables. Although in Hawaii seasons may vary little in temperature and many vegetables can be grown year around, some will do better when planted within the given time frame.

Broccoli and lettuce are cool season vegetables. As long as the temperatures remain cool, the lettuce will continue to produce tender leaves, and the broccoli flower buds will remain closed.

Generally lettuce and broccoli are planted from September through March/April. During the hot summer months plants can bolt.

At higher elevations, cool season vegetables such as lettuce, broccoli, cauliflower, chard and mustard may be successful planted in late spring and summer. The warm season vegetables include tomatoes, cucumbers, melons, squash, peppers, corn and eggplant.

See my website — — and search “cool season vegetables.”

In March, I will be teaching a class on growing vegetables and further discussing this topic. The class is offered through the University of Hawaii at Hilo College of Continuing Education and Community Service.

Hi, Nick. Thanks for your column. It’s very helpful. I planted four podocarpus bushes a few years ago to serve as a hedge between our neighbor’s property and ours. The bushes are now an ideal height — 8 feet tall. I need to get on a ladder to keep the tops trimmed. Is there anything I can apply to the soil that would slow or stop their growth? I don’t want them getting any higher. Is there any method for height control, other than physically trimming them? Mahalo. — Teri

For all practical purposes, lopers and chainsaws are the principal method for trimming podocarpus.

There is such a thing as chemical pruning; applying an herbicide to the tree or to the ground underneath. These chemicals, which are actually plant growth regulator, will cause the growth between the nodes to be shortened. Bonzi, Cutlass and Embark are three such chemicals. They are expensive and registered in Hawaii for commercial use only. They are used mostly in grower nurseries to cause uniform growth in ornamental plants such as poinsettias. I don’t know of any research conducted on podocarpus.

Dear Nick, I found your blog online while researching blueberry propagation. I’m currently working on a farm near Hilo. I’m trying to get some info on the best way to propagate blueberry bushes. My current thought is to cut softwood sprigs off the top of the plant, place them in a perlite/peat moss mixture and mist them throughout the day. Do you have any advice? Do you think a greenhouse is necessary? Do you know anything about softwood vs hardwood propagation? Thanks. — Liza

Blueberries are propagated from either softwood or hardwood cuttings. You might choose hardwood cuttings since they are collected in late January or February, after sufficient chilling has occurred. Here are some helpful directions:

1. Select healthy material.

2. Avoid propagating from plants that have odd-looking or stunted foliage.

3. Collect shoots from the previous summer, 12 to 36 inches in length.

4. Divide these shoots into pieces 5 to 6 inches long, removing any flower buds.

5. Place cuttings in a propagation bed at a depth of one-half to two-thirds of their length. Keep moist.

Softwood cuttings are taken in late spring from the current season’s growth, 4 to 5 inches long. Collect these cuttings when the stems have developed woody tissue but are still somewhat flexible. Remove all leaves with the exception of two or three terminal leaves. Place cuttings in the propagation bed, under mist at a depth of one-half to two-thirds of their length.

Rooted cuttings are eventually transplanted into pots and held for about one year. During the time of rooting, keep beds moist while being aware not to over water.

For the propagation process, a greenhouse is not necessary, but some type of propagation bed/chamber, under 40-70 percent shade with a mist system is recommended; an area as small as 3-by-3-by-3 can be used.

The mist system should keep the media uniformly moist but not soggy. An intermittent-mist system with frequent, short misting intervals is recommended in order to keep the humidity near 100 percent. However, keeping the cuttings at this constant moisture also creates an ideal environment for pathogenic fungi to grow.

Thus cleanliness is very important; use new or sterilized planting mix and pots, keeping them raised off the ground.

Potting media containing various mixtures of coarse sand, ground pine bark, perlite, sawdust, and peat moss have proven satisfactory. According to the UH publication, a good rooting medium recipe is a mixtures of coarse sand, ground pine bark, and peat moss (1:1:1) or perlite and peat moss (1:1)

For more details, read the UH Cooperative Extension publication found online at

Hilo resident Nick Sakovich is a professor emeritus of the University of California. He has worked in the field of agriculture for 30 years. Email your questions to Sakovich at