monspessulana samples from its native range and the majority of invasive French broom samples from California. Chloroplast and nuclear phylogenetic analyses revealed a clade containing G. Our results suggest multiple origins of invasive French broom in California. These samples were used to reconstruct a phylogeny of brooms using two chloroplast ( trnL-F spacer and tRNA-leu intron) and two nuclear (ITS and ETS) DNA regions. To address these objectives, we collected samples from 25 invasive French broom populations from a range of altitudes and habitats throughout California, six landscape plantings, seven horticultural outlets, and nine botanical gardens and arboreta from its native range. The goals of this research are to: i) identify the cultivated sources of invasive broom populations in California, and ii) determine whether hybridization between ornamental cultivars, species, and naturalized populations has occurred. It is no longer available commercially, but its close relative, sweet broom, assumed to be Genista racemosa, is a popular ornamental and may be contributing to invasive populations. French broom, believed to be Genista monspessulana, was introduced into California by the horticultural industry and has caused serious environmental damage throughout the state. Evidence of hybridization is important because it can increase invasiveness and make management, particularly biological control, difficult. These invaders are often difficult to identify due to hybridization among ornamental cultivars and species, and naturalized populations. Take care not to cut beyond where the plant begins to branch, as the shrub will then be bushier as it grows back.The horticultural trade provides a major pathway for the introduction of invasive plants. This means cutting or sawing all branches down to a height of approximately 40 cm. However, if you do not prune the broom on a regular basis, vigorous pruning is still recommended every three to four years. Of course, you may simply want to trim your broom into shape, or prevent it from becoming larger than intended. In the third year the last of the old branches can be cut down and now the entire plant will then have been rejuvenated. Repeat this process the following year, selecting about half of the remaining ‘old’ branches for removal. If you want to rejuvenate your broom through pruning you need to select about one third of the branches, divided evenly over the shrub, and cut these down to about 40 cm from the ground. If you do this in autumn or winter you will reduce the number of flowers your shrub produces the following summer. If you leave this until it is fully grown, it is too late to avoid it looking dishevelled and you will be unable to reshape it by trimming.īroken or diseased branches can be pruned at any time but when pruning the size and shape the best time for this is at the end of May, after flowering. If you start before it is mature and do this annually you will keep it looking its best. It is important to start trimming the tree while it is still young. But, you must know when and how to prune your broom to avoid missing your chance. This may be required due to broken or diseased branches or it may just have outgrown its space, becoming wild and untidy. Pruning the broomīroom responds well to pruning. This is why pruning broom is essential, whether you just want to tidy it up or cut it right back. This fast development, along with a wide branching root system and thick stems, has caused the plant to become quite invasive. These small-to-large shrubs grow very quickly. Scotch has a five-sided stem while Spanish appears almost round. There are several varieties but the most common are the Scotch and Spanish. It has angled stems, small leaves and bright yellow spring flowers. The broom, or cytisus praecox, is a shrub that can grow anywhere from three to about ten feet tall.
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