It was established that during budding, for various optical and biological structures of crops, marigold (calendula as medicinal plant) competed unequally with weeds for light, water and nourishment. Thus, the distance between plants in a row within 20 cm, was found in crops of 20 to 35 pcs. / m2 of annual weeds, their weight varied from 10,2 to 17,9 g/m². It was found 2-4 pcs. / m² of perennial weeds sand their weight was 4,3-8,6 g/m².

By reducing the distance between plants in the row planting of medicinal calendula had higher density, thereby reducing the number and weight of weeds. Thus, it was found from 14 to 24 pcs. /m² of annual weeds with weight from 7,1 to 12,2 g/m² when the distance between plants in a row was within 10 cm of sowing. The number and weight of perennial weeds were from 2 pcs./m² to 4,3 g/m².

The most noticeable weed infestation indicator varied depending on sowing time. Thus, by planting in the first period, the number of annual weeds per 1 m2 was 14-23 pcs., and weight – 7,11-11,7 g. At sowing culture in the second period, the number of annual weeds grew to 16-27 pcs., and weight to 8,2-13,8 g/m². It was observed the biggest quantity and weight of annual weeds – 21-35 pcs., and 10,7-17,9 g in the second sowing.

Consequently, it was found that in the later terms of sowing crop of marigold with annual weeds growing reached to 4-11 pcs./m². Weed-infested indicators of crops were decreased by 6-21 pcs./m² reducing the distance between plants in the row and row spacing to 30 cm.

Besides weeds, diseases caused significant damage to marigold growth. According to scientists, in Ukraine the most common diseases of this medicinal plant are mildew (Erysiphe communis), fusarium wilting (Fusarium), and tserkosporoz and peronosporoz. To prevent the development of these diseases, the authors recommend: to put into effect crop rotation and cultivation farming; to destroy the impressed remains of plants; to sow healthy seeds.

Thus, in the period of sprouts, the lowest prevalence of the disease – 6% and the degree of affect by plants – 12% was observed in the second sowing, while the first term variations of these values were on average 12 and 16%.

In the budding marigold phase for sowing in the first and second periods, the prevalence of the disease was 7 and 12%, and impressed plants – 14 and 19%. These data suggest the spread of diseases in crops. Moderately cold weather with plenty of moisture affected sprouts of medicinal calendula. As a result of field observations and records it was found that fusarium wilt can affect not only the root system of sprouts, primordial leaves and root collar of young plants, but often the disease can spread from sick to healthy plants through the transfer of infectious agents, affecting leaves and buds on later stages of growth and development.

Thus, sowing crops for the first time, the percentage of fusarium wilt infected plants of marigold in full blooming phase increased by an average of 5 points - regardless of the distance between plants. The degree of plant infestation increased by 3% compared with the corresponding figures in the previous phase of plant growth and development.

The range of fusarium wilt disease in crops of medicinal calendula continued to the end of the growing season. It was revealed the same trends.

Key words: marigold as medicinal plant, lines of sowing, methods of sowing, weeds, fusarium wilt desease.